WorldWideScience

Sample records for plasma poloidal magnetic

  1. Experimental Measurement of Asymmetric Fluctuations of Poloidal Magnetic Field in Damavand Tokomak at Different Plasma Currents

    Science.gov (United States)

    Moslehi-Fard, Mahmoud; Alinejad, Naser; Rasouli, Chapar; Sadigzadeh, Asghar

    2012-08-01

    Toroidal and Poloidal magnetic fields have an important effect on the tokomak topology. Damavand Tokomak is a small size tokomak characterized with k = 1.2, B t = 1T, R 0 = 36 cm, maximum plasma current is about 35 KA with a discharge time of 21 ms. In this experimental work, the variation of poloidal magnetic field on the torodial cross section is measured and analyzed. In order to measure the polodial magnetic field, 18 probes were installed on the edge of tokomak plasma with ∆θ = 18°, while a limiter was installed inside the torus. Plasma current, I p, induces a polodial magnetic field, B p, smaller than the torodial magnetic field B t. Magnetic lines B produced as a combination of B t and B p, are localized on the nested toroidal magnetic surfaces. The presence of polodial magnetic field is necessary for particles confinement. Mirnov oscillations are the fluctuations of polodial magnetic field, detected by magnetic probes. Disrupted instability in Tokomak typically starts with mirnov oscillations which appear as fluctuations of polodial magnetic field and is detected by magnetic probes. Minor disruptions inside the plasma can contain principal magnetic islands and their satellites can cause the annihilation of plasma confinement. Production of thin layer of turbulent magnetic field lines cause minor disruption. Magnetic limiter may cause the deformation of symmetric equilibrium configuration and chaotic magnetic islands reveal in plasma occurring in thin region of chaotic field lines close to their separatrix. The width of this chaotic layer in the right side of poloidal profile of Damavand Tokomak is smaller than the width in the left side profile because of Shafranov displacement. Ergodic region in the left side of profile develops a perturbation on the magnetic polodial field lines, B p, that are greater in magnitude than that in the right side, although the values of B p on the left side are smaller than that on the right side of the profile. The Left

  2. Main Cause of the Poloidal Plasma Motion Inside a Magnetic Cloud Inferred from Multiple-Spacecraft Observations

    Science.gov (United States)

    Zhao, Ake; Wang, Yuming; Chi, Yutian; Liu, Jiajia; Shen, Chenglong; Liu, Rui

    2017-04-01

    Although the dynamical evolution of magnetic clouds (MCs) has been one of the foci of interplanetary physics for decades, only few studies focus on the internal properties of large-scale MCs. Recent work by Wang et al. ( J. Geophys. Res. 120, 1543, 2015) suggested the existence of the poloidal plasma motion in MCs. However, the main cause of this motion is not clear. In order to find it, we identify and reconstruct the MC observed by the Solar Terrestrial Relations Observatory (STEREO)-A, Wind, and STEREO-B spacecraft during 19 - 20 November 2007 with the aid of the velocity-modified cylindrical force-free flux-rope model. We analyze the plasma velocity in the plane perpendicular to the MC axis. It is found that there was evident poloidal motion at Wind and STEREO-B, but this was not clear at STEREO-A, which suggests a local cause rather than a global cause for the poloidal plasma motion inside the MC. The rotational directions of the solar wind and MC plasma at the two sides of the MC boundary are found to be consistent, and the values of the rotational speeds of the solar wind and MC plasma at the three spacecraft show a rough correlation. All of these results illustrate that the interaction with ambient solar wind through viscosity might be one of the local causes of the poloidal motion. Additionally, we propose another possible local cause: the existence of a pressure gradient in the MC. The significant difference in the total pressure at the three spacecraft suggests that this speculation is perhaps correct.

  3. On the toroidal current density flowing across a poloidal-magnetic-field null in an axisymmetric plasma

    Science.gov (United States)

    Rodrigues, Paulo; Bizarro, João P. S.

    2013-04-01

    The axisymmetry condition and two of Maxwell's equations are used to show that, in general, there are no nested magnetic surfaces around a poloidal-magnetic-field null for a sufficiently small value of the toroidal current density flowing there. Hence, the toroidal current density at the axis of a magnetic configuration with extreme shear reversal cannot continuously approach zero unless nested surfaces are first broken or particular values are assigned to boundary conditions and other plasma parameters. The threshold of the toroidal current-density at which the topology changes is shown to be set by such parameters, and some examples of the predicted topology transition are presented using analytical solutions of the Grad-Shafranov equation.

  4. On the toroidal current density flowing across a poloidal-magnetic-field null in an axisymmetric plasma

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Paulo; Bizarro, Joao P. S. [Associacao Euratom-IST, Instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, 1049-001 Lisboa (Portugal)

    2013-04-15

    The axisymmetry condition and two of Maxwell's equations are used to show that, in general, there are no nested magnetic surfaces around a poloidal-magnetic-field null for a sufficiently small value of the toroidal current density flowing there. Hence, the toroidal current density at the axis of a magnetic configuration with extreme shear reversal cannot continuously approach zero unless nested surfaces are first broken or particular values are assigned to boundary conditions and other plasma parameters. The threshold of the toroidal current-density at which the topology changes is shown to be set by such parameters, and some examples of the predicted topology transition are presented using analytical solutions of the Grad-Shafranov equation.

  5. Self organization of high βp plasma equilibrium with an inboard poloidal magnetic field null in QUEST

    Science.gov (United States)

    Mishra, Kishore; Zushi, H.; Idei, H.; Hasegawa, M.; Onchi, T.; Tashima, S.; Banerjee, S.; Hanada, H.; Togashi, H.; Yamaguchi, T.; Ejiri, A.; Takase, Y.; Nakamura, K.; Fujisawa, A.; Nagashima, Y.; Kuzmin, A.; QUEST Team

    2015-08-01

    Successful production of high βp plasmas (ɛβp ⩾ 1) fully non-inductively (NI) and their long pulse sustainment with the help of modest power (<100 kW) of electron cyclotron waves is demonstrated. High βp plasmas are found for the first time to be naturally self organized to form a stable natural inboard poloidal field null (IPN) equilibrium. A critical βp value is identified, which defines the transition boundary from inboard limiter (IL) to IPN equilibrium. A new feature of plasma self organization is evidenced, which enhances its negative triangular shape to sustain high βp. These results show a relatively simple method to produce and sustain high βp plasma close to the equilibrium limit in a stable configuration exploiting its self organization property.

  6. Strongly magnetized accretion discs require poloidal flux

    Science.gov (United States)

    Salvesen, Greg; Armitage, Philip J.; Simon, Jacob B.; Begelman, Mitchell C.

    2016-08-01

    Motivated by indirect observational evidence for strongly magnetized accretion discs around black holes, and the novel theoretical properties of such solutions, we investigate how a strong magnetization state can develop and persist. To this end, we perform local simulations of accretion discs with an initially purely toroidal magnetic field of equipartition strength. We demonstrate that discs with zero net vertical magnetic flux and realistic boundary conditions cannot sustain a strong toroidal field. However, a magnetic pressure-dominated disc can form from an initial configuration with a sufficient amount of net vertical flux and realistic boundary conditions. Our results suggest that poloidal flux is a necessary prerequisite for the sustainability of strongly magnetized accretion discs.

  7. Strongly magnetized accretion discs require poloidal flux

    CERN Document Server

    Salvesen, Greg; Simon, Jacob B; Begelman, Mitchell C

    2016-01-01

    Motivated by indirect observational evidence for strongly magnetized accretion discs around black holes, and the novel theoretical properties of such solutions, we investigate how a strong magnetization state can develop and persist. To this end, we perform local simulations of accretion discs with an initially purely toroidal magnetic field of equipartition strength. We demonstrate that discs with zero net vertical magnetic flux and realistic boundary conditions cannot sustain a strong toroidal field. However, a magnetic pressure-dominated disc can form from an initial configuration with a sufficient amount of net vertical flux and realistic boundary conditions. Our results suggest that poloidal flux is a necessary prerequisite for the sustainability of strongly magnetized accretion discs.

  8. Poloidal rotation induced by injecting lower hybrid waves in tokamak plasma edge

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The poloidal rotation of the magnetized edge plasma in tokamak driven by theponderomotive force which is generated by injecting lower hybrid wave(LHW) electric field hasbeen studied. The LHW is launched from a waveguide in the plasma edge, and by Brambilla’sgrill theory, analytic expressions for the wave electric field in the slab model of an inhomogeneouscold plasma have been derived. It is shown that a strong wave electric field will be generated inthe plasma edge by injecting LH wave of the power in MW magnitude, and this electric field willinduce a poloidal rotation with a sheared poloidal velocity.PACS: 52.55.Fa

  9. Toroidal and poloidal magnetic fields at Venus. Venus Express observations

    Science.gov (United States)

    Dubinin, E.; Fraenz, M.; Woch, J.; Zhang, T. L.; Wei, Y.; Fedorov, A.; Barabash, S.; Lundin, R.

    2013-10-01

    Magnetic field and plasma measurements carried out onboard Venus Express during solar minimum conditions suggest the existence of two kinds of magnetic field configuration in the Venusian ionosphere. We interpret these as the manifestation of two different types of generation mechanisms for the induced magnetosphere. A different magnetic field topology (toroidal and poloidal) arises if the induced currents are driven either by the solar wind motional electric field or by the Faraday electric field—a conducting ionosphere sees the magnetic field carried by solar wind as a time-varying field. At the dayside, both driving agents produce a similar draping pattern of the magnetic field. However, different magnetic field signatures inherent to both induction mechanisms appear at lower altitudes in the terminator region. The conditions at low solar EUV flux when the ionosphere of Venus becomes magnetized seem to be favorable to distinguish between two different types of the induced fields. We present cases of both types of the magnetic field topology. The cases when the effects of the Faraday induction become well noticeable are especially interesting since they provide us with an example of solar wind interaction with a tiny induced dipole field immersed into the ionosphere. Another interesting case when poloidal magnetic fields are evidently displayed is observed when the IMF vector is almost aligned with the solar wind velocity. In general case, both mechanisms of induction probably complement each other.

  10. Application of poloidal beta and plasma internal inductance in determination of input power time of Damavand tokamak

    Science.gov (United States)

    Noori, Ehsanallah; Sadeghi, Yahya; Ghoranneviss, Mahmood

    2016-10-01

    In this study, magnetic measurement of poloidal fields were used to determine poloidal beta and plasma internal inductance of Damavand tokamak combination of poloidal beta and plasma internal inductance (β _p+{l_i}/{2} ), known as Shafranov parameter, was obtained experimentally in terms of normal and tangential components of the magnetic field. Plasma internal inductance and poloidal beta were obtained using parametrization method based on analytical solution of Grad-Shafranov equation (GSE) and compared with parabolic-like profile of toroidal current density approach for determination of the plasma internal inductance. Finding evolution of β _p+{l_i}/{2} and plasma internal inductance. Finding poloidal beta (Shafranov parameter and internal inductance) and using energy balance equation, thermal energy and energy confinement were determined qualitatively in terms of poloidal beta during a regular discharge of Damavand tokamak.

  11. Control of neo-classical double tearing modes by differential poloidal rotation in reversed magnetic shear tokamak plasmas

    Science.gov (United States)

    Wang, Jialei; Wang, Zheng-Xiong; Wei, Lai; Liu, Yue

    2017-04-01

    The control of neo-classical tearing modes (NTMs) by the differential rotation in the reversed magnetic shear (RMS) configuration with different separations Δ {{r}\\text{s}} between two rational surfaces is numerically studied by means of reduced magnetohydrodynamic (MHD) simulations. It is found that the differential rotation with a strong shear at the outer resonant surface can effectively suppress the explosive burst of double tearing modes (DTMs)/NTMs. Critical values of the strength of rotation to suppress the burst are also presented for different bootstrap current fractions {{f}\\text{b}} . Furthermore, a couple of measurable parameters ≤ft(δ, κ \\right) , corresponding respectively to the triangularity and elongation of the magnetic islands at the outer resonant surface, are introduced to characterize the deformation of islands in the nonlinear phase. It is found that the triangularity δ is more likely to precisely predict the onset of burst than the island width w and elongation κ . For a given Δ {{r}\\text{s}} , the critical value of triangularity {δ\\text{crit}} is obtained by scanning different plasma parameters. Establishing such a database of ≤ft(δ,κ \\right) is helpful to effectively control the development of NTMs in the RMS experimental discharges.

  12. Gyrokinetic simulations predict anomalous poloidal rotation in tokamak plasmas

    Science.gov (United States)

    Dif-Pradalier, Guilhem; Grandgirard, Virginie; Sarazin, Yanick; Garbet, Xavier; Ghendrih, Phillippe; Angelino, Paolo

    2008-11-01

    First-principle based collisionless gyrokinetic theory consensually provides today's deepest insight on turbulence-related problems in plasma physics. Conversely, neoclassical theory describes the effects of binary Coulomb collisions in a toroidal and inhomogeneous magnetic geometry and its consequences on particle trapping. The interplay between turbulence and collisions is a subject of great current focus for first-principle modeling since recent evidences have started to emphasise its relevance for the onset and the control of enhanced confinement regimes in the next-generation devices like Iter. A finite differences Fokker-Planck ion-ion collision operator is implemented in the full-f and global GYSELA code and has been thoroughly benchmarked in neoclassical regimes. Two types of simulations are compared, either purely neoclassical or turbulent including neoclassical effects. In each case, three different values of collisionality in the banana regime are investigated. Preliminary results show an enhancement of about 30% of the poloidal rotation of the main ions (Z=1) in the turbulent regime as compared to its neoclassical value. In all cases the radial force balance equation is satisfied within a few percent. Most of this increase comes from the radial electric field.

  13. Effects of the poloidal variation of the magnetic field ripple on enhanced heat transport in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Uckan, N.A.; Tsang, K.T.; Callen, J.D.

    1976-06-01

    The use of a finite number of coils to generate the toroidal field of a tokamak introduces a magnetic field asymmetry and is responsible for an additional particle trapping that can affect the plasma confinement. The enhanced transport coefficients associated with the ripple-induced drifts have been calculated. The calculations include both the radial and poloidal variation in the magnitude of the field ripple. It is found that the consideration of poloidal variation significantly reduces the ripple-trapped transport but does not affect the banana-drift diffusion. Results relevant to the ORNL Experimental Power Reactor (EPR) reference design are discussed.

  14. Detailed characterization of laser-produced astrophysically-relevant jets formed via a poloidal magnetic nozzle

    Science.gov (United States)

    Higginson, D. P.; Revet, G.; Khiar, B.; Béard, J.; Blecher, M.; Borghesi, M.; Burdonov, K.; Chen, S. N.; Filippov, E.; Khaghani, D.; Naughton, K.; Pépin, H.; Pikuz, S.; Portugall, O.; Riconda, C.; Riquier, R.; Ryazantsev, S. N.; Skobelev, I. Yu.; Soloviev, A.; Starodubtsev, M.; Vinci, T.; Willi, O.; Ciardi, A.; Fuchs, J.

    2017-06-01

    The collimation of astrophysically-relevant plasma ejecta in the form of narrow jets via a poloidal magnetic field is studied experimentally by irradiating a target situated in a 20 T axial magnetic field with a 40 J, 0.6 ns, 0.7 mm diameter, high-power laser. The dynamics of the plasma shaping by the magnetic field are studied over 70 ns and up to 20 mm from the source by diagnosing the electron density, temperature and optical self-emission. These show that the initial expansion of the plasma is highly magnetized, which leads to the formation of a cavity structure when the kinetic plasma pressure compresses the magnetic field, resulting in an oblique shock [A. Ciardi et al., Phys. Rev. Lett. 110, 025002 (2013)]. The resulting poloidal magnetic nozzle collimates the plasma into a narrow jet [B. Albertazzi et al., Science 346, 325 (2014)]. At distances far from the target, the jet is only marginally magnetized and maintains a high aspect ratio due to its high Mach-number (M ∼ 20) and not due to external magnetic pressure. The formation of the jet is evaluated over a range of laser intensities (1012-1013 W/cm2), target materials and orientations of the magnetic field. Plasma cavity formation is observed in all cases and the viability of long-range jet formation is found to be dependent on the orientation of the magnetic field.

  15. Resonant magnetic perturbations and divertor footprints in poloidally diverted tokamaks

    CERN Document Server

    Cahyna, Pavel

    2010-01-01

    General formula describing both the divertor strike point splitting and width of magnetic islands created by resonant magnetic perturbations (RMPs) in a poloidally diverted tokamak equilibrium is derived. Under the assumption that the RMP is produced by coils at the low-field side such as those used to control edge localized modes (ELMs) it is demonstrated that the width of islands on different magnetic surfaces at the edge and the amount of divertor splitting are related to each other. Explanation is provided of aligned maxima of the perturbation spectra with the safety factor profile - an effect empirically observed in models of many perturbation coil designs.

  16. An analytic determination of beta poloidal and internal inductance in an elongated tokamak from magnetic probe measurements

    Energy Technology Data Exchange (ETDEWEB)

    Sorci, J.M.

    1992-02-01

    Analytic calculations of the magnetic fields available to magnetic diagnostics are performed for tokamaks with circular and elliptical cross sections. The explicit dependence of the magnetic fields on the poloidal beta and internal inductances is sought. For tokamaks with circular cross sections, Shafranov's results are reproduced and extended. To first order in the inverse aspect ratio expansion of the magnetic fields, only a specific combination of beta poloidal and internal inductance is found to be measurable. To second order in the expansion, the measurements of beta poloidal and the internal inductance are demonstrated to be separable but excessively sensitive to experimental error. For tokamaks with elliptical cross sections, magnetic measurements are found to determine beta poloidal and the internal inductance separately. A second harmonic component of the zeroth order field in combination with the dc harmonic of the zeroth order field specifies the internal inductance. The internal inductance in hand, measurement of the first order, first harmonic component of the magnetic field then determined beta poloidal. The degeneracy implicit in Shafranov's result (i.e. that only a combination of beta poloidal and internal inductance is measurable for a circular plasma cross section) reasserts itself as the elliptic results are collapsed to their circular limits.

  17. An analytic determination of beta poloidal and internal inductance in an elongated tokamak from magnetic probe measurements

    Energy Technology Data Exchange (ETDEWEB)

    Sorci, J.M.

    1992-02-01

    Analytic calculations of the magnetic fields available to magnetic diagnostics are performed for tokamaks with circular and elliptical cross sections. The explicit dependence of the magnetic fields on the poloidal beta and internal inductances is sought. For tokamaks with circular cross sections, Shafranov`s results are reproduced and extended. To first order in the inverse aspect ratio expansion of the magnetic fields, only a specific combination of beta poloidal and internal inductance is found to be measurable. To second order in the expansion, the measurements of beta poloidal and the internal inductance are demonstrated to be separable but excessively sensitive to experimental error. For tokamaks with elliptical cross sections, magnetic measurements are found to determine beta poloidal and the internal inductance separately. A second harmonic component of the zeroth order field in combination with the dc harmonic of the zeroth order field specifies the internal inductance. The internal inductance in hand, measurement of the first order, first harmonic component of the magnetic field then determined beta poloidal. The degeneracy implicit in Shafranov`s result (i.e. that only a combination of beta poloidal and internal inductance is measurable for a circular plasma cross section) reasserts itself as the elliptic results are collapsed to their circular limits.

  18. Prototype detectors for measuring poloidal magnetic flux with an ion beam probe

    Science.gov (United States)

    Crowley, T. P.; Demers, D. R.; Fimognari, P. J.; Kile, T. D.

    2016-10-01

    Development of a detector and associated techniques to determine the localized magnetic flux, and therefore poloidal magnetic field and current density profile, in an axisymmetric plasma device is underway. This will provide invaluable information on equilibrium, transport and stability studies of fusion plasmas. A singly charged ion beam is injected into the plasma and the detector located outside the plasma measures doubly charged ions created within a cm-scale sample volume of the plasma. The ions are split into beamlets at the detector. The toroidal angle of the beam's velocity is determined by measuring the fraction of the beamlets that strike detection plates and wires. The corresponding angle is used to determine the beam's toroidal velocity component. Due to canonical momentum conservation, that toroidal velocity is proportional to the poloidal flux function in the sample volume. We have built several prototype detectors and measured the angle of a 45 keV potassium ion beam. The cross-section of the plasma that can be studied will be maximized and system costs will be minimized if the detector has a direct view of the plasma and is operated close to it. However, this subjects the detector to noise due to UV-induced photoelectrons and plasma particles. We have conducted experiments that demonstrate reductions of this noise to facilitate measurement of ion beam signals. Experimental and design results will be presented. This work is supported by US DoE Award No. DE-SC0006077.

  19. Modelling the influence of temperature anisotropies on poloidal asymmetries of density in the core of rotating plasmas

    Science.gov (United States)

    Bilato, R.; Maj, O.; Angioni, C.

    2014-07-01

    A consistent set of equations is derived to model poloidal density asymmetries induced by temperature anisotropies in tokamak rotating plasmas. The model can be applied to compute poloidal density asymmetry of highly charged impurities due to additional plasma heating.

  20. Hall Equilibria: Solutions with toroidal and poloidal magnetic fields in Neutron Star Crusts

    CERN Document Server

    Gourgouliatos, K N; Lyutikov, M; Reisenegger, A

    2013-01-01

    We present Hall equilibrium solutions for neutron stars crusts containing toroidal and poloidal magnetic field. Some simple cases are solved analytically while more complicated configurations are found numerically through a Gauss-Seidel elliptic partial differential equation solver.

  1. The effect of magnetic resistivity in advection dominated accretion disk with poloidal magnetic

    Directory of Open Access Journals (Sweden)

    J Ghanbari

    2009-12-01

    Full Text Available In this work, we carry out self –similar solutions of viscous-resistive accretion flows around a magnetized compact object. We consider an axi-symmetric, rotating, isothermal steady accretion flow, which contains a poloidal magnetic field of the central star. The dominant mechanism of energy dissipation is assumed to be the turbulence viscosity and magnetic diffusivity due to the magnetic field of the central star. We explore the effect of viscosity, magnetic diffusivity and advection on a rotating disk. We show that dynamical quantities of advection dominated accretion flows (ADAFs are sensitive to the advection, viscosity and magnetic diffusivity parameters.

  2. Toroidal and poloidal plasma rotation measurements in Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Hess, W.R.; Garbet, X.; Guirlet, R.; Hesse, M.; Payan, J. [Association Euratom-CEA, Centre d`Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee

    1993-12-31

    Plasma rotation measurements by visible spectroscopy and by a CO{sub 2}-laser scattering experiment (ALTAIR) are presented. The ALTAIR diagnostic is used to study the turbulence changes at the plasma edge during operation of the ergodic divertor (ED). Heterodyne detection allows discrimination between waves propagating in the electron or in the ion diamagnetic direction. (author) 6 refs., 4 figs.

  3. Poloidal OHMIC heating in a multipole

    Energy Technology Data Exchange (ETDEWEB)

    Holly, D.J.

    1982-01-01

    The feasibility of using poloidal currents to heat plasmas confined by a multipole field has been examined experimentaly in Tokapole II. The machine is operated as a toroidal octupole, with a time-varying toroidal magnetic field driving poloidal plasma currents I/sub plasma/ - 20 kA to give densities n/sub e/ - 10/sup 13/ cm/sup -3/ and temperatures T/sub e/ - 30 eV.

  4. Magnetic field pitch angle and perpendicular velocity measurements from multi-point time-delay estimation of poloidal correlation reflectometry

    Science.gov (United States)

    Prisiazhniuk, D.; Krämer-Flecken, A.; Conway, G. D.; Happel, T.; Lebschy, A.; Manz, P.; Nikolaeva, V.; Stroth, U.; the ASDEX Upgrade Team

    2017-02-01

    In fusion machines, turbulent eddies are expected to be aligned with the direction of the magnetic field lines and to propagate in the perpendicular direction. Time delay measurements of density fluctuations can be used to calculate the magnetic field pitch angle α and perpendicular velocity {{v}\\bot} profiles. The method is applied to poloidal correlation reflectometry installed at ASDEX Upgrade and TEXTOR, which measure density fluctuations from poloidally and toroidally separated antennas. Validation of the method is achieved by comparing the perpendicular velocity (composed of the E× B drift and the phase velocity of turbulence {{v}\\bot}={{v}E× B}+{{v}\\text{ph}} ) with Doppler reflectometry measurements and with neoclassical {{v}E× B} calculations. An important condition for the application of the method is the presence of turbulence with a sufficiently long decorrelation time. It is shown that at the shear layer the decorrelation time is reduced, limiting the application of the method. The magnetic field pitch angle measured by this method shows the expected dependence on the magnetic field, plasma current and radial position. The profile of the pitch angle reproduces the expected shape and values. However, comparison with the equilibrium reconstruction code cliste suggests an additional inclination of turbulent eddies at the pedestal position (2-3°). This additional angle decreases towards the core and at the edge.

  5. Non-Newtonian viscosity in magnetized plasma

    CERN Document Server

    Johnson, Robert W

    2007-01-01

    The particle and momentum balance equations can be solved on concentric circular flux surfaces to determine the effective viscous drag present in a magnetized tokamak plasma in the low aspect ratio limit. An analysis is developed utilizing the first-order Fourier expansion of the poloidal variation of quantities on the flux surface akin to that by Stacey and Sigmar [Phys. Fluids, 28, 9 (1985)]. Expressions to determine the poloidal variations of density, poloidal velocity, toroidal velocity, radial electric field, poloidal electric field, and other radial profiles are presented in a multi-species setting. Using as input experimental data for the flux surface averaged profiles of density, temperature, toroidal current, toroidal momentum injection, and the poloidal and toroidal rotations of at least one species of ion, one may solve the equations numerically for the remaining profiles. The resultant effective viscosities are compared to those predicted by Stacey and Sigmar and Shaing, et al., [Nuclear Fusion, 2...

  6. Deuterium-tritium TFTR plasmas in the high poloidal beta regime

    Energy Technology Data Exchange (ETDEWEB)

    Sabbagh, S.A.; Mauel, M.E.; Navratil, G.A. [Columbia Univ., New York, NY (United States). Dept. of Applied Physics] [and others

    1995-03-01

    Deuterium-tritium plasmas with enhanced energy confinement and stability have been produced in the high poloidal beta, advanced tokamak regime in TFTR. Confinement enhancement H {triple_bond} {tau}{sub E}/{tau}{sub E ITER-89P} > 4 has been obtained in a limiter H-mode configuration at moderate plasma current I{sub p} = 0.85 {minus} 1.46 MA. By peaking the plasma current profile, {beta}{sub N dia} {triple_bond} 10{sup 8} < {beta}{sub t{perpendicular}} > aB{sub 0}/I{sub p} = 3 has been obtained in these plasma,s exceeding the {beta}{sub N} limit for TFTR plasmas with lower internal inductance, l{sub i}. Fusion power exceeding 6.7 MW with a fusion power gain Q{sub DT} = 0.22 has been produced with reduced alpha particle first orbit loss provided by the increased l{sub i}.

  7. Global Observations of Magnetospheric High-m Poloidal Waves During the 22 June 2015 Magnetic Storm

    Science.gov (United States)

    Le, G.; Chi, P. J.; Strangeway, R. J.; Russell, C. T.; Slavin, J. A.; Takahashi, K.; Singer, H. J.; Anderson, B. J.; Bromund, K.; Fischer, D.; hide

    2017-01-01

    We report global observations of high-m poloidal waves during the recovery phase of the 22 June 2015 magnetic storm from a constellation of widely spaced satellites of five missions including Magnetospheric Multiscale (MMS), Van Allen Probes, Time History of Events and Macroscale Interactions during Substorm (THEMIS), Cluster, and Geostationary Operational Environmental Satellites (GOES). The combined observations demonstrate the global spatial extent of storm time poloidal waves. MMS observations confirm high azimuthal wave numbers (m approximately 100). Mode identification indicates the waves are associated with the second harmonic of field line resonances. The wave frequencies exhibit a decreasing trend as L increases, distinguishing them from the single-frequency global poloidal modes normally observed during quiet times. Detailed examination of the instantaneous frequency reveals discrete spatial structures with step-like frequency changes along L. Each discrete L shell has a steady wave frequency and spans about 1 RE, suggesting that there exist a discrete number of drift-bounce resonance regions across L shells during storm times.

  8. Observing and modelling the poloidal and toroidal magnetic fields of the global dynamo

    Science.gov (United States)

    Cameron, Robert; Duvall, Thomas; Schüssler, Manfred; Schunker, Hannah

    2017-08-01

    The large scale solar dynamo is a cycle where poloidal flux is generated from toroidal flux, and toroidal flux is generated from poloidal flux. The toroidal and poloidal fields can be inferred from observations, and the Babcock-Leighton model shows how differential rotation and flux emergence explain the observed evolution of the fields.

  9. 2D profile of poloidal magnetic field diagnosed by a laser-driven ion-beam trace probe (LITP)

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoyi; Xiao, Chijie, E-mail: cjxiao@pku.edu.cn; Chen, Yihang; Xu, Tianchao; Lin, Chen [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Wang, Long [Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China); Xu, Min [Center for Fusion Science of Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041 (China); Yu, Yi [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026 (China)

    2016-11-15

    Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (B{sub p}) and radial electric field (E{sub r}) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D B{sub p} profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.

  10. 2D profile of poloidal magnetic field diagnosed by a laser-driven ion-beam trace probe (LITP)

    Science.gov (United States)

    Yang, Xiaoyi; Xiao, Chijie; Chen, Yihang; Xu, Tianchao; Lin, Chen; Wang, Long; Xu, Min; Yu, Yi

    2016-11-01

    Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (Bp) and radial electric field (Er) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D Bp profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.

  11. Upgrading of the Magnetic Confinement Plasma Device KT-5E

    Institute of Scientific and Technical Information of China (English)

    何迎花; 余羿; 闻一之; 刘万东; 李定; 俞昌旋; 谢锦林; 李弘; 兰涛; 王昊宇

    2012-01-01

    In this article we present ideas of providing appropriate poloidal magnetic field for helimaks to help to generate toroidal magnetic plasma torus. Placing a conductive ring in the center of the cross-section to induce a suitable current, we change the helical magnetic field lines in the helimak discharge into magnetic surface. In this kind of discharge, the plasma density is greatly increased, and the corresponding density fluctuation is significantly decreased, showing a better confinement by magnetic shear. It allows more flexible and efficient experimental investigations on the toroidal magnetic confinement plasmas to be carried on in this kind of device.

  12. Poloidal beta and internal inductance measurement on HT-7 superconducting tokamak.

    Science.gov (United States)

    Shen, B; Sun, Y W; Wan, B N; Qian, J P

    2007-09-01

    Poloidal beta beta(theta) and internal inductance l(i) measurements are very important for tokamak operation. Much more plasma parameters can be inferred from the two parameters, such as the plasma energy confinement time, the plasma toroidal current profile, and magnetohydrodynamics instability. Using diamagnetic and compensation loop, combining with poloidal magnetic probe array signals, poloidal beta beta(theta) and internal inductance l(i) are measured. In this article, the measurement system and arithmetic are introduced. Different experimental results are given in different plasma discharges on HT-7 superconducting tokamak.

  13. Computational Study of Poloidal Angular Momentum Transport in DIII-D

    Science.gov (United States)

    Pankin, Alexei; Kruger, Scott; Kritz, Arnold; Rafiq, Tariq; Weiland, Jan

    2013-10-01

    The new Multi-Mode Model, MMM8.1, includes the capability to predict the anomalous poloidal momentum diffusivity [T. Rafiq et al., Phys. Plasmas 20, 032506 (2013)]. It is important to consider the effect of this diffusivity on the poloidal rotation of tokamak plasmas since some experimental observations suggest that neoclassical effects are not always sufficient to explain the observed poloidal rotation [B.A. Grierson et al., Phys. Plasmas 19, 056107 (2012)]. One of the objectives of this research is to determine if the anomalous contribution to the poloidal rotation can be significant in the regions of internal transport barriers (ITBs). In this study, the MMM8.1 model is used to compute the poloidal momentum diffusivity for a range of plasma parameters that correspond to the parameters that occur in DIII-D discharges. The parameters that are considered include the temperature and density gradients, and magnetic shear. The role of anomalous poloidal transport in the possible poloidal spin up in the ITB regions is discussed. Progress in the implementation of poloidal transport equations in the ASTRA transport code is reported and initial predictive simulation results for the poloidal rotation profiles are presented. This research is partially support by the DOE Grants DE-SC0006629 and DE-FG02-92ER54141.

  14. Inertial-Acoustic Oscillations of Black-Hole Accretion Discs with Large-Scale Poloidal Magnetic Fields

    CERN Document Server

    Yu, Cong

    2015-01-01

    We study the effect of large-scale magnetic fields on the non-axisymmetric inertial-acoustic modes (also called p-modes) trapped in the innermost regions of accretion discs around black holes (BHs). These global modes could provide an explanation for the high-frequency quasi-periodic oscillations (HFQPOs) observed in BH X-ray binaries. There may be observational evidence for the presence of such large-scale magnetic fields in the disks since episodic jets are observed in the same spectral state when HFQPOs are detected. We find that a large-scale poloidal magnetic field can enhance the corotational instability and increase the growth rate of the purely hydrodynamic overstable p-modes. In addition, we show that the frequencies of these overstable p-modes could be further reduced by such magnetic fields, making them agree better with observations.

  15. Efficient magnetic fields for supporting toroidal plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Landreman, Matt, E-mail: mattland@umd.edu [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States); Boozer, Allen H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

    2016-03-15

    The magnetic field that supports tokamak and stellarator plasmas must be produced by coils well separated from the plasma. However, the larger the separation, the more difficult it is to produce a given magnetic field in the plasma region, so plasma configurations should be chosen that can be supported as efficiently as possible by distant coils. The efficiency of an externally generated magnetic field is a measure of the field's shaping component magnitude at the plasma compared to the magnitude near the coils; the efficiency of a plasma equilibrium can be measured using the efficiency of the required external shaping field. Counterintuitively, plasma shapes with low curvature and spectral width may have low efficiency, whereas plasma shapes with sharp edges may have high efficiency. Two precise measures of magnetic field efficiency, which correctly identify such differences in difficulty, will be examined. These measures, which can be expressed as matrices, relate the externally produced normal magnetic field on the plasma surface to the either the normal field or current on a distant control surface. A singular value decomposition (SVD) of either matrix yields an efficiency ordered basis for the magnetic field distributions. Calculations are carried out for both tokamak and stellarator cases. For axisymmetric surfaces with circular cross-section, the SVD is calculated analytically, and the range of poloidal and toroidal mode numbers that can be controlled to a given desired level is determined. If formulated properly, these efficiency measures are independent of the coordinates used to parameterize the surfaces.

  16. Effect of a localized magnetic perturbation on magnetic islands in a cylindrical plasma

    Energy Technology Data Exchange (ETDEWEB)

    Bateman, G; Morris, R N

    1980-05-01

    A self-consistent plasma equilibrium model is developed to study the width or ergodic regions and magnetic islands in a periodic cylindrical plasma under the influence of a localized magnetic perturbation, such as that produced by a bundle divertor or ripple coil set. It is found that localized perturbations tend to produce poloidally symmetric annular ergodic regions and poloidally elongated magnetic islands rather than simple magnetic islands. Our plasma model takes into account the flattening of the current profile across each annular ergodic region and the concommitant steepening of the current profile between ergodic regions. Using current profiles inferred from experimental data, saturated tearing mode amplitudes are computed and found to agree with the experimentally observed Mirnov oscillation amplitudes. As the applied magnetic perturbation is turned on and increased, it is observed that the steepened current profile and resulting enhancement of tearing modes produces wider ergodic regions than would be expected from the vacuum magnetic perturbation alone.

  17. Magnetic Fluctuation Measurement in Sino United Spherical Tokamak Plasma

    Institute of Scientific and Technical Information of China (English)

    LIU Fei; WANG Wen-Hao; HE Ye-Xi; LIU Jun; TAN Yi; XIE Li-Feng; ZENG Long

    2007-01-01

    To investigate the magnetic fluctuations and for further transport study, the poloidal and radial magnetic field measurement is conducted on the Sino United Spherical Tokamak (SUNIST). Auto-power spectral density indicates that the magnetic fluctuation energy mainly concentrates in the frequency region lower than 10kHz. The magnetic field oscillations, which are characterized by harmonic frequencies of 40 kHz, are observed in the scrapeoff layer; by contrast, in the plasma core, the magnetic fluctuations are of Gaussian type. The time-frequency profiles show that the poloidal magnetic fluctuations are temporally intermittent. The autocorrelation calculation indicates that the fluctuations in decorrelation time vary between the core and the edge.

  18. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak.

    Science.gov (United States)

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-01

    An X-mode polarized V band (50 GHz-75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz-19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from -1 km/s to -3 km/s.

  19. Variational calculation of neoclassical ion heat flux and poloidal flow in the banana regime for axisymmetric magnetic geometry

    Science.gov (United States)

    Parker, Jeffrey B.; Catto, Peter J.

    2012-08-01

    We present a numerical solution of the drift-kinetic equation retaining the linearized Fokker-Planck collision operator which is valid for general axisymmetric magnetic geometry in the low collisionality limit. We use the well-known variational principle based on entropy production and expand in basis functions. Uniquely, we expand in pitch-angle basis functions which are eigenfunctions of the transit-averaged test particle collision operator. These eigenfunctions, which depend on the geometry, are extremely well suited to this problem, with only one or two basis functions required to obtain an accurate solution. As a simple example of the technique, the neoclassical ion heat flux and poloidal flow are calculated for circular flux surfaces and compared with analytic approximations for arbitrary aspect ratio.

  20. GEM detector development for tokamak plasma radiation diagnostics: SXR poloidal tomography

    Science.gov (United States)

    Chernyshova, Maryna; Malinowski, Karol; Ziółkowski, Adam; Kowalska-Strzeciwilk, Ewa; Czarski, Tomasz; Poźniak, Krzysztof T.; Kasprowicz, Grzegorz; Zabołotny, Wojciech; Wojeński, Andrzej; Kolasiński, Piotr; Krawczyk, Rafał D.

    2015-09-01

    An increased attention to tungsten material is related to a fact that it became a main candidate for the plasma facing material in ITER and future fusion reactor. The proposed work refers to the studies of W influence on the plasma performances by developing new detectors based on Gas Electron Multiplier GEM) technology for tomographic studies of tungsten transport in ITER-oriented tokamaks, e.g. WEST project. It presents current stage of design and developing of cylindrically bent SXR GEM detector construction for horizontal port implementation. Concept to overcome an influence of constraints on vertical port has been also presented. It is expected that the detecting unit under development, when implemented, will add to the safe operation of tokamak bringing creation of sustainable nuclear fusion reactors a step closer.

  1. Tokamak Plasmas : Internal magnetic field measurement in tokamak plasmas using a Zeeman polarimeter

    Indian Academy of Sciences (India)

    M Jagadeeshwari; J Govindarajan

    2000-11-01

    In a tokamak plasma, the poloidal magnetic field profile closely depends on the current density profile. We can deduce the internal magnetic field from the analysis of circular polarization of the spectral lines emitted by the plasma. The theory of the measurement and a detailed design of the Zeeman polarimeter constructed to measure the poloidal field profile in the ADITYA tokamak are presented. The Fabry-Perot which we have employed in our design, with photodiode arrays followed by lock-in detection of the polarization signal, allows the measurement of the fractional circular polarization. In this system He-II line with wavelength 4686 Å is adopted as the monitoring spectral line. The line emission used in the present measurement is not well localized in the plasma, necessiating the use of a spatial inversion procedure to obtain the local values of the field.

  2. Impact of poloidal convective cells on momentum flux in tokamaks

    Science.gov (United States)

    Garbet, X.; Asahi, Y.; Donnel, P.; Ehrlacher, C.; Dif-Pradalier, G.; Ghendrih, P.; Grandgirard, V.; Sarazin, Y.

    2017-01-01

    Radial fluxes of parallel momentum due to E× B and magnetic drifts are shown to be correlated in tokamak plasmas. This correlation comes from the onset of poloidal convective cells generated by turbulence. The entire process requires a symmetry breaking mechanism, e.g. a mean shear flow. An analytical calculation shows that anti-correlation between the poloidal and parallel components of the turbulent Reynolds stress results in anti-correlation of the fluxes of parallel momentum generated by E× B and curvature drifts.

  3. Magnetic configuration control of ITER plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Albanese, R.; Mattei, M. [Assoc. Euratom-ENEA-CREATE, Univ. Mediterranea RC, Loc. Feo di Vito I-89060, RC (Italy); Portone, A. [EFDA-CSU, Max Planck Institute for Plasmaphysics, Boltzmannstrasse 2, D-85748 Garching (Germany)], E-mail: alfredo.portone@tech.efda.org; Ambrosino, G. [Assoc. Euratom-ENEA-CREATE, University Napoli Federico II, Via Claudio 21, I-80125 Naples (Italy); Artaserse, G. [Assoc. Euratom-ENEA-CREATE, Univ. Mediterranea RC, Loc. Feo di Vito I-89060, RC (Italy); Crisanti, F. [Associazione EURATOM-ENEA sulla Fusione, Frascati, C.P. 65, 00044-Frascati (Italy); De Tommasi, G. [Assoc. Euratom-ENEA-CREATE, University Napoli Federico II, Via Claudio 21, I-80125 Naples (Italy); Fresa, R. [DIFA, University della Basilicata, Contrada Macchia Romana I-85100, PZ (Italy); Sartori, F. [Euratom/UKAEA Fusion Assoc., Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Villone, F. [Assoc. Euratom-ENEA-CREATE, University Cassino, Via Di Biasio 43, I-03043 Cassino (Italy)

    2007-10-15

    The aim of this paper is to present some new tools used to review the capability of the ITER Poloidal Field (PF) system in controlling the broad range of plasma configurations presently forecasted during ITER operation. The attention is focused on the axi-symmetric aspects of plasma magnetic configuration control since they pose the greatest challenges in terms of control power and they have the largest impact on machine capital cost. Some preliminary results obtained during ongoing activities in collaboration between ENEA/CREATE and EFDA are presented. The paper is divided in two main parts devoted, respectively, to the presentation of a procedure for the PF current optimisation during the scenario, and of a software environment for the study of the PF system capabilities using the plasma linearized response. The proposed PF current optimisation procedure is then used to assess Scenario 2 design, also taking into account the presence of axisymmetric eddy currents and possible variations of poloidal beta and internal inductance. The numerical linear model based tool derived from the JET oriented eXtreme Shape Controller (XSC) tools is finally used to obtain results on the strike point sweeping in ITER.

  4. Toroidal vs. poloidal magnetic fields in Sun-like stars: a rotation threshold

    CERN Document Server

    Petit, P; Solanki, SK; Donati, J-F; Aurière, M; Lignières, F; Morin, J; Paletou, F; Ramírez, J; Catala, C; Fares, R

    2008-01-01

    From a set of stellar spectropolarimetric observations, we report the detection of surface magnetic fields in a sample of four solar-type stars, namely HD 73350, HD 76151, HD 146233 and HD 190771. Assuming that the observed variability of polarimetric signal is controlled by stellar rotation, we establish the rotation periods of our targets, with values ranging from 8.8 d (for HD 190771) to 22.7 d (for HD 146233). Apart from rotation, fundamental parameters of the selected objects are very close to the Sun's, making this sample a practical basis to investigate the specific impact of rotation on magnetic properties of Sun-like stars. We reconstruct the large-scale magnetic geometry of the targets as a low-order (l<10) spherical harmonics expansion of the surface magnetic field. From the set of magnetic maps, we draw two main conclusions. (a) The magnetic energy of the large-scale field increases with rotation rate. The increase of chromospheric emission with the mean magnetic field is flatter than observed ...

  5. Neutral-beam current-driven high-poloidal-beta operation of the DIII-D tokamak

    Science.gov (United States)

    Simonen, T. C.; Matsuoka, M.; Bhadra, D. K.; Burrell, K. H.; Callis, R. W.; Chance, M. S.; Chu, M. S.; Greene, J. M.; Groebner, R. J.; Harvey, R. W.; Hill, D. N.; Kim, J.; Lao, L.; Petersen, P. I.; Porter, G. D.; St. John, H.; Stallard, B. W.; Stambaugh, R. D.; Strait, E. J.; Taylor, T. S.

    1988-10-01

    Neutral-beam current-drive experiments in the DIII-D tokamak with a single null poloidal divertor are described. A plasma current of 0.34 MA has been sustained by neutral beams alone, and the energy confinement is of H-mode quality. Poloidal β values reach 3.5 without disruption or coherent magnetic activity suggesting that these plasmas may be entering the second stability regime.

  6. Experimental investigation of magnetically confined plasma loops

    Energy Technology Data Exchange (ETDEWEB)

    Tenfelde, Jan

    2012-12-11

    Arch-shaped magnetic flux tubes generated in a pulsed-power plasma experiment were investigated with a variety of diagnostics concerning their expansion properties. Specifically, the expansion velocity was of interest, which is observed as constant for a wide range of experimental parameters. An MHD transport mechanism is investigated as possible cause of a uniform arch cross section: Axial transport of poloidal magnetic flux along the plasma may cause a pinch force leading to a uniform diameter along the arch. Despite numerous experimental findings at a very similar experimental setup, no indication for the relevance of this process could be found. Instead, magnetic probe data showed that the plasma current in the apex region is constant. A constant expansion velocity was observed for considerably different experimental conditions. This included different plasma source designs with fundamentally different toroidal magnetic field topology and variation of the working gas, which lead to plasma densities lower by an order of magnitude. Inside the current channel of the arch, Alfven velocities were estimated. To this end, plasma density profiles obtained from interferometry were inverted to obtain local densities, which were in turn verified by means of Stark broadening of hydrogen Balmer lines. Furthermore, measurements of multiple components of the magnetic field of the plasma arch were performed. An estimate for the conductivity was obtained from Spitzer's formula for fully ionized plasma using electron temperatures obtained from elementary optical emission spectroscopy. From the presented data of ccd imaging, magnetic field probes, and to lesser extent, interferometry, the underlying assumption of residual plasma (and considerable plasma currents through it) below the actual arch structure is very plausible. Rough estimates of the electric field strength along the arch and results of the magnetic field measurements showed, that the detected expansion

  7. Starfire poloidal coil systems

    Energy Technology Data Exchange (ETDEWEB)

    Evans, K. Jr.; Kim, S.H.; Turner, L.R.; Wang, S.T.

    1980-01-01

    The poloidal coils for STARFIRE consists of three systems: (1) equilibrium field (EF) coils; (2) ohmic heating (OH) coils; and (3) correction field (CF) coils. The EF coils are superconducting and lie outside the toroidal field (TF) coils. These coils provide the bulk of the equilibrium field necessary to keep the plasma positioned in the vacuum chamber with the desired cross sectional shape and pressure and current distributions. Having these coils outside of the TF coils requires that they have a larger stored energy and larger currents but eases the assembly, maintenance, and reliability of the coils. The STARFIRE OH system is relatively small compared to tokamaks in which the current is entirely ohmically driven. It is designed to provide sufficient flux in the early startup to raise the plasma current to the point (1 to 2 MA) where the rf current drive can take over.

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

    Science.gov (United States)

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

    2013-10-01

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

  9. Dynamics of resonant magnetic field penetration and plasma rotation

    Science.gov (United States)

    Ivanov, N. V.; Kakurin, A. M.

    2017-01-01

    Results of calculations and analysis of the penetration of resonant magnetic perturbations (RMP) into tokamak plasma are presented. The TEAR code used for the calculations is based on a two-fluid magnetohydrodynamics approximation that gives coupled diffusion-type equations for the magnetic flux perturbation and for plasma rotation velocities in toroidal and poloidal directions. The radial distribution of the magnetic flux perturbation is calculated taking account of an externally applied RMP and magnetic perturbation generated by an eddy current in the resistive-vacuum vessel. The decoupling of magnetic-island velocity from the velocity of plasma rotation is employed in the calculations according to available experimental evidence and corresponding theoretical understanding. The account of this decoupling, as well as of plasma rotation in the poloidal direction in addition to the toroidal one, reduces the RMP penetration threshold and accelerates the penetration process. The main attention is paid to the dependences of the RMP penetration dynamics on the simulation conditions. The simulation findings are compared with available experimental data. Some predictions of the penetration threshold values for ITER conditions are presented.

  10. Ion temperature gradient driven mode in presence of transverse velocity shear in magnetized plasmas

    DEFF Research Database (Denmark)

    Chakrabarti, N.; Juul Rasmussen, J.; Michelsen, Poul

    2005-01-01

    The effect of sheared poloidal flow on the toroidal branch of the ion temperature gradient driven mode of magnetized nonuniform plasma is studied. A novel "nonmodal" calculation is used to analyze the problem. It is shown that the transverse shear flow considerably reduced the growth...

  11. Heat flux and plasma flow in the scrape off layer on the spherical tokamak QUEST with inboard poloidal field null configuration

    Science.gov (United States)

    Onchi, Takumi; Zushi, Hideki; Mishra, Kishore; Hanada, Kazuaki; Idei, Hiroshi; Nakamura, Kazuo; Fujisawa, Akihide; Nagashima, Yoshihiko; Hasegawa, Makoto; Kuzmin, Arseny; Nagaoka, Kenichi; QUEST Team

    2014-10-01

    Heat flux and plasma flow in the scrape off layer (SOL) are examined in the inboard poloidal null (IPN) configuration on the spherical tokamak (ST) QUEST. In the ST, trapped energetic electrons on the low field side are widely excursed from the last closed flux surface to SOL so that significant heat loss occurs. Interestingly, plasma flows in the core and the SOL are also observed in IPN though no inductive force like ohmic heating is applied. High heat flux (>1 MW/m2) and sonic flow (M > 1) in far-SOL arise in current ramp-up phase. In quasi-steady state, sawtooth-like oscillation of plasma current with 20 Hz has been observed. Heat flux and subsonic plasma flow in far-SOL are well correlated to plasma current oscillation. The toroidal Mach number largely increases from Mφ ~ 0.1 to ~ 0.5 and drops although the amplitude of plasma current is about 10% of that. Note that such flow modification occurs before plasma current crash, there may be some possibility that phenomena in the SOL or the edge trigger reactions in the core plasma. This work is supported by Grants-in-aid for Scientific Research (S24226020), NIFS Collaboration Research Program (NIFS12KUTR081), and the Collaborative Research Program of Research Institute for Applied Mechanics, Kyushu University.

  12. Magnetized and collimated millimeter scale plasma jets with astrophysical relevance

    Energy Technology Data Exchange (ETDEWEB)

    Brady, Parrish C.; Quevedo, Hernan J. [Texas Center for High Intensity Laser Science, University of Texas at Austin, Austin, Texas 78712 (United States); Valanju, Prashant M. [Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712-1060 (United States); Bengtson, Roger D.; Ditmire, Todd [Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

    2012-01-15

    Magnetized collimated plasma jets are created in the laboratory to extend our understanding of plasma jet acceleration and collimation mechanisms with particular connection to astrophysical jets. In this study, plasma collimated jets are formed from supersonic unmagnetized flows, mimicking a stellar wind, subject to currents and magnetohydrodynamic forces. It is found that an external poloidal magnetic field, like the ones found anchored to accretion disks, is essential to stabilize the jets against current-driven instabilities. The maximum jet length before instabilities develop is proportional to the field strength and the length threshold agrees well with Kruskal-Shafranov theory. The plasma evolution is modeled qualitatively using MHD theory of current-carrying flux tubes showing that jet acceleration and collimation arise as a result of electromagnetic forces.

  13. Nonlinear plasma wave in magnetized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Bulanov, Sergei V. [Kansai Photon Science Institute, JAEA, Kizugawa, Kyoto 619-0215 (Japan); Prokhorov Institute of General Physics, Russian Academy of Sciences, Moscow 119991 (Russian Federation); Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region 141700 (Russian Federation); Esirkepov, Timur Zh.; Kando, Masaki; Koga, James K. [Kansai Photon Science Institute, JAEA, Kizugawa, Kyoto 619-0215 (Japan); Hosokai, Tomonao; Zhidkov, Alexei G. [Photon Pioneers Center, Osaka University, 2-8 Yamadaoka, Suita, Osaka 565-0871 (Japan); Japan Science and Technology Agency, CREST, 2-1, Yamadaoka, Suita, Osaka 565-0871 (Japan); Kodama, Ryosuke [Photon Pioneers Center, Osaka University, 2-8 Yamadaoka, Suita, Osaka 565-0871 (Japan); Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)

    2013-08-15

    Nonlinear axisymmetric cylindrical plasma oscillations in magnetized collisionless plasmas are a model for the electron fluid collapse on the axis behind an ultrashort relativisically intense laser pulse exciting a plasma wake wave. We present an analytical description of the strongly nonlinear oscillations showing that the magnetic field prevents closing of the cavity formed behind the laser pulse. This effect is demonstrated with 3D PIC simulations of the laser-plasma interaction. An analysis of the betatron oscillations of fast electrons in the presence of the magnetic field reveals a characteristic “Four-Ray Star” pattern.

  14. Experimental Identification of the Kink Instability as a Poloidal Flux Amplification Mechanism for Coaxial Gun Spheromak Formation

    OpenAIRE

    Hsu, S. C.; Bellan, P. M.

    2003-01-01

    The magnetohydrodynamic kink instability is observed and identified experimentally as a poloidal flux amplification mechanism for coaxial gun spheromak formation. Plasmas in this experiment fall into three distinct regimes which depend on the peak gun current to magnetic flux ratio, with (I) low values resulting in a straight plasma column with helical magnetic field, (II) intermediate values leading to kinking of the column axis, and (III) high values leading immediately to a detached plasma...

  15. Experimental Identification of the Kink Instability as a Poloidal Flux Amplification Mechanism for Coaxial Gun Spheromak Formation

    CERN Document Server

    Hsu, S C

    2003-01-01

    The magnetohydrodynamic kink instability is observed and identified experimentally as a poloidal flux amplification mechanism for coaxial gun spheromak formation. Plasmas in this experiment fall into three distinct regimes which depend on the peak gun current to magnetic flux ratio, with (I) low values resulting in a straight plasma column with helical magnetic field, (II) intermediate values leading to kinking of the column axis, and (III) high values leading immediately to a detached plasma. Onset of column kinking agrees quantitatively with the Kruskal-Shafranov limit, and the kink acts as a dynamo which converts toroidal to poloidal flux. Regime~II clearly leads to both poloidal flux amplification and the development of a spheromak configuration.

  16. Experimental identification of the kink instability as a poloidal flux amplification mechanism for coaxial gun spheromak formation.

    Science.gov (United States)

    Hsu, S C; Bellan, P M

    2003-05-30

    The magnetohydrodynamic kink instability is observed and identified experimentally as a poloidal flux amplification mechanism for coaxial gun spheromak formation. Plasmas in this experiment fall into three distinct regimes which depend on the peak gun current to magnetic flux ratio, with (I) low values resulting in a straight plasma column with helical magnetic field, (II) intermediate values leading to kinking of the column axis, and (III) high values leading immediately to a detached plasma. Onset of column kinking agrees quantitatively with the Kruskal-Shafranov limit, and the kink acts as a dynamo which converts toroidal to poloidal flux. Regime II clearly leads to both poloidal flux amplification and the development of a spheromak configuration.

  17. Spheromak reactor with poloidal flux-amplifying transformer

    Science.gov (United States)

    Furth, Harold P.; Janos, Alan C.; Uyama, Tadao; Yamada, Masaaki

    1987-01-01

    An inductive transformer in the form of a solenoidal coils aligned along the major axis of a flux core induces poloidal flux along the flux core's axis. The current in the solenoidal coil is then reversed resulting in a poloidal flux swing and the conversion of a portion of the poloidal flux to a toroidal flux in generating a spheromak plasma wherein equilibrium approaches a force-free, minimum Taylor state during plasma formation, independent of the initial conditions or details of the formation. The spheromak plasma is sustained with the Taylor state maintained by oscillating the currents in the poloidal and toroidal field coils within the plasma-forming flux core. The poloidal flux transformer may be used either as an amplifier stage in a moving plasma reactor scenario for initial production of a spheromak plasma or as a method for sustaining a stationary plasma and further heating it. The solenoidal coil embodiment of the poloidal flux transformer can alternately be used in combination with a center conductive cylinder aligned along the length and outside of the solenoidal coil. This poloidal flux-amplifying inductive transformer approach allows for a relaxation of demanding current carrying requirements on the spheromak reactor's flux core, reduces plasma contamination arising from high voltage electrode discharge, and improves the efficiency of poloidal flux injection.

  18. Plasma convection near the magnetic null of a snowflake divertor during an ELM event

    Energy Technology Data Exchange (ETDEWEB)

    Ryutov, D.D.; Cohen, R.H.; Rognlien, T.D.; Umansky, M.V. [Lawrence Livermore National Laboratory, Livermore, CA (United States)

    2012-06-15

    A snowflake magnetic configuration is created in a tokamak when the poloidal magnetic field and its first spatial derivatives become zero at a certain point. The separatrix then acquires a characteristic hexagonal shape reminiscent of a snowflake. We study new features of the plasma macroscopic equilibrium and stability in the vicinity of the snowflake null. We note that, compared to the standard X-point divertor, the zone of weak poloidal magnetic field is much larger. The weak poloidal field leads to development of intense plasma convection over the expanded area around the null-point during the ejection phase of an edge localized mode (ELM) event when the plasma pressure in the scrape-off layer increases compared to its inter-ELM value. Intense convection may lead to a roughly-equal splitting of the heat flux between the 4 snowflake divertor legs and to a broadening of the plasma wetted area in each leg, thereby mitigating damage to divertor plates (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Nonlinear Plasma Wave in Magnetized Plasmas

    CERN Document Server

    Bulanov, Sergei V; Kando, Masaki; Koga, James K; Hosokai, Tomonao; Zhidkov, Alexei G; Kodama, Ryosuke

    2013-01-01

    Nonlinear axisymmetric cylindrical plasma oscillations in magnetized collisionless plasmas are a model for the electron fluid collapse on the axis behind an ultrashort relativisically intense laser pulse exciting a plasma wake wave. We present an analytical description of the strongly nonlinear oscillations showing that the magnetic field prevents closing of the cavity formed behind the laser pulse. This effect is demonstrated with 3D PIC simulations of the laser-plasma interaction. An analysis of the betatron oscillations of fast electrons in the presence of the magnetic field reveals a characteristic "Four-Ray Star" pattern which has been observed in the image of the electron bunch in experiments [T. Hosokai, et al., Phys. Rev. Lett. 97, 075004 (2006)].

  20. Turbulent transport in magnetized plasmas

    CERN Document Server

    Horton, Wendell

    2012-01-01

    This book explains how magnetized plasmas self-organize in states of electromagnetic turbulence that transports particles and energy out of the core plasma faster than anticipated by the fusion scientists designing magnetic confinement systems in the 20th century. It describes theory, experiments and simulations in a unified and up-to-date presentation of the issues of achieving nuclear fusion power.

  1. On plasma edge ideal MHD stability/instability condition in Mercier stable magnetic hill configurations

    Science.gov (United States)

    Shchepetov, S. V.

    2016-11-01

    The stability of peeling modes in zero net current stellarator plasma is studied in high poloidal mode number m \\gg 1 approximation. The vacuum region solution is taken into account. Under these conditions in Mercier stable magnetic hill plasmas internal peeling modes are stable. External peeling modes can be unstable, but several limitations on them are found. It is shown that an analytically derived pressure gradient threshold is in reasonable agreement with the experimental observations and numerical calculations. The threshold decreases with increasing poloidal mode number m. It is shown, however, that higher modes may be stabilized due to finite ion Larmor radius effects. For the sake of definiteness, we have investigated peeling mode behavior in Mercier unstable plasma. It is shown that both external and internal peeling modes can be unstable in this regime. However, external and internal peeling modes in this case are definitely different.

  2. A Probe Head for Simultaneous Measurements of Electrostatic and Magnetic Fluctuations in ASDEX Upgrade Edge Plasma

    DEFF Research Database (Denmark)

    Schrittwieser, R W; Ionita, C; Vianello, N

    2010-01-01

    For ASDEX Upgrade (AUG) a new probe head was developed for simultaneous measurements of electric and magnetic fluctuations in the edge plasma region. The probe head consists of a cylindrical graphite case. On the front side six graphite pins are mounted. With this arrangement the poloidal and rad...... is inserted up to three times for 100 ms each by the midplane manipulator into the scrape-off layer. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim....

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

    Science.gov (United States)

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

    2014-10-01

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

  4. Experimental investigation in plasma relaxation by using a compact coaxial magnetized plasma gun in a background plasma

    Science.gov (United States)

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

    2012-10-01

    A compact coaxial plasma gun is employed for experimental studies of plasma relaxation process being conducted in the HELCAT device at UNM. These studies will advance the knowledge of basic plasma physics in the areas of magnetic relaxation and space and astrophysical plasmas, including the evolution of active galactic jets/radio lobes. The gun is powered by a 120pF ignitron-switched capacitor bank which is operated in a range of 5 - 10kV. Multiple diagnostics are employed to investigate plasma relaxation process. Magnetized Argon plasma bubbles with velocities 1.2Cs and densities 10e20 m-3 have been achieved. Different distinct regimes of operation with qualitatively different dynamics are identified by fast CCD camera images, with the parameter lambda determining the operation regime. Additionally, a B-dot probe array is employed to measure the spatial toroidal and poloidal magnetic flux evolution to identify detached plasma bubble configurations. Experimental data and analysis will be presented.

  5. Equilibrium poloidal field distributions in reversed-field-pinch toroidal discharges

    Energy Technology Data Exchange (ETDEWEB)

    Baker, D.A.; Mann, L.W.; Schoenberg, K.F.

    1982-04-01

    A comparison between the analytic formulae of Shafranov for equilibrium in axisymmetric toroidal reversed field pinch (RFP) systems and fully toroidal numerical solutions of the Grad-Shafranov equation is presented as a function of poloidal beta, internal plasma inductance, and aspect ratio. The Shafranov formula for the equilibrium poloidal field distribution is accurate to within 5% for aspect ratios greater than 2, poloidal betas less than 50%, and for plasma current channels that exceed one-third of the minor toroidal radius. The analytic description for the center shift of the innermost flux surface that encloses the plasma current (the Shafranov shift) is accurate to within 15% for aspect ratios greater than 2 and poloidal betas below 50%, provided the shift does not exceed one-tenth of the minor conducting boundary radius. The behavior of the magnetic axis shift as a function of plasma parameters is included. The Shafranov formulae provide a convenient method for describing the equilibrium behavior of an RFP discharge. Examples illustrating the application of the analytic formulae to the Los Alamos ZT-40M RFP experiment are given.

  6. Measurement of Poloidal Velocity on the National Spherical Torus Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Ronald E. Bell and Russell Feder

    2010-06-04

    A diagnostic suite has been developed to measure impurity poloidal flow using charge exchange recombination spectroscopy on the National Spherical Torus Experiment. Toroidal and poloidal viewing systems measure all quantities required to determine the radial electric field. Two sets of up/down symmetric poloidal views are used to measure both active emission in the plane of the neutral heating beams and background emission in a radial plane away from the neutral beams. Differential velocity measurements isolate the line-integrated poloidal velocity from apparent flows due to the energy-dependent chargeexchange cross section. Six f/1.8 spectrometers measure 276 spectra to obtain 75 active and 63 background channels every 10 ms. Local measurements from a similar midplane toroidal viewing system are mapped into two dimensions to allow the inversion of poloidal line-integrated measurements to obtain local poloidal velocity profiles. Radial resolution after inversion is 0.6-1.8 cm from the plasma edge to the center.

  7. Induction of poloidal rotation by mean of a ponderomotive force; Induccion de rotacion poloidal por medio de una fuerza ponderomotriz

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez T, C. [Instituto Nacional de Investigaciones Nucleares, Departamento de Fisica, Salazar, Estado de Mexico, C.P. 52045 (Mexico); Martinell, J. [Instituto de Ciencias Nucleares, UNAM, C.P. 04510, Mexico D.F. (Mexico)

    1999-07-01

    When a plasma is radiated with a radiofrequency wave (RF) with fluxes of energy at hundred megawatts order (MW) the effect the of ponderomotive force (PM) is very important. This force applied to the plasma column can generate a rotation movement by a non-resonant mechanism. Particularly, it is known that the poloidal rotation can be induced by direct action of the PM force poloidal moment. This poloidal rotation of the plasma column can to explain the appearance of high confinement regime (H) in Tokamaks. In this work, it is analysed this mechanism, showing that if it is operated efficiently with the poloidal and parallel components of PM force then could be intensified the poloidal rotation moreover it is showed the form in which the asymptotic value of this rotation is established. (Author)

  8. In What Magnetic Environment Are Coronal Loop Plasmas Located?

    Science.gov (United States)

    Lim, Daye; Choe, Gwang-Son

    2017-08-01

    As for coronal loops, there is a conventional wisdom that the plasma is confined inside magnetic flux tubes. However, a plasma pressure profile, which decreases from the center of a flux rope to its periphery, can be ideal MHD interchange unstable if field line ends are freely movable. In the solar corona, the strong line-tying condition impedes the interchange of the positions of elementary flux tubes, but ubiquitous magnetic reconnection processes can change plasma distribution in such a way that the system moves to a more stable state with a lower energy. In this study, we investigate the plasma redistribution in the merging process of many small flux ropes possibly representing loop strands, by an MHD simulation. We have found that the redistributed plasma is more concentrated between flux ropes rather than near the center of individual flux ropes. When flux ropes initially have different amounts of twists, the plasma tends to accumulate in less twisted regions. As larger and larger flux ropes are formed by successive merging processes, the ratio of poloidal flux to toroidal flux in a merged flux rope becomes smaller and smaller, i.e., field lines are less and less twisted. Our study may explain why the observed coronal loops appear very little twisted and quite well ordered in spite of continuous entangling motions in the photosphere and below.

  9. Dusty Sheaths in Magnetized Plasmas

    Institute of Scientific and Technical Information of China (English)

    Yu. I. Chutov; O. Yu. Kravchenko; S. Masuzaki; A. Sagara; R. D. Smirnov; Yu. Tomita

    2004-01-01

    Parameters of self-consistent magnetized dusty sheaths are investigated using computer simulations of a temporal evolution of one-dimensional slab plasma with dust particles. The evolution is caused by a collection of electrons and ions by both a wall (electrode) and dust particles, which are initially immersed into plasma and distributed in front of the electrode. Obtained results show the existence of oscillations of a self-consistent potential in magnetized dusty sheaths including boundary potentials. Dust particles weaken magnetized sheaths and create additional sheaths close to a boundary of dust particles. The magnetic field does not influence on the dust particle charge.

  10. Simultaneous Measurements of Electrostatic and Magnetic Fluctuations in ASDEX Upgrade Edge Plasma

    DEFF Research Database (Denmark)

    Ionita, Codrina; Vianello, Nicola; Müller, H.W.

    2009-01-01

    in such a way that simultaneously the poloidal and radial electric field components, the ion saturation current and the current-voltage characteristic can be registered. During the AUG discharges of 7 s lengths the probe head is inserted two to three times for 100 ms each by the midplane manipulator......In ASDEX Upgrade (AUG) electrostatic and magnetic fluctuations in the edge plasma region were measured simultaneously during ELMy H-mode (high confinement) plasmas and L-mode (low confinement) plasmas and during a transition between the two modes. A special probe was used containing six Langmuir...

  11. Magnetic Instabilities Driven by Sheared Toroidal and Poloidal Flows in the limit of B=0. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Foster, Cary B.

    2000-08-08

    The grant was used for startup activity in an experiment designed to address key questions related to the MHD dynamo, a process by which kinetic energy in flowing, conducting fluids can spontaneously be converted into magnetic energy. Dynamos have been invoked to explain the magnetic fields associated with the planets, stars and other astrophysical bodies. The experiment consists primarily of a 1 meter diameter sphere of liquid sodium with flows driven by mechanical propellers.

  12. Shock formation induced by poloidal flow and its effects on the edge stability in tokamaks

    Science.gov (United States)

    Seol, Jaechun; Shaing, Kerchung; Aydemir, Ahmet

    2016-10-01

    In the high confinement mode of tokamaks, magnitude of the radial electric field increases at the edge. Thus, the poloidal flow inside the transport barrier can be sonic when the edge pressure gradient is not steep enough to make the poloidal flow subsonic. When the poloidal Mach number is close to unity, a shock appears in the low field side and causes a large density perturbation. In this study, we describe a shock induced by the sonic poloidal plasma flow. Then, an entropy production across the shock is calculated. Finally, we introduce a simple model for Type III edge localized modes using the poloidal density variation driven by the sonic poloidal flow.

  13. 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.

  14. Control of the Helicity Content of a Gun-Generated Spheromak by Incorporating a Conducting Shell into a Magnetized Coaxial Plasma Gun

    Science.gov (United States)

    Matsumoto, Tadafumi; Sekiguchi, Jun'ichi; Asai, Tomohiko

    In the formation of magnetized plasmoid by a magnetized coaxial plasma gun (MCPG), the magnetic helicity content of the generated plasmoid is one of the critical parameters. Typically, the bias coil to generate a poloidal flux is mounted either on the outer electrode or inside the inner electrode. However, most of the flux generated in the conventional method spreads even radially outside of the formation region. Thus, only a fraction of the total magnetic flux is actually exploited for helicity generation in the plasmoid. In the proposed system, the plasma gun incorporates a copper shell mounted on the outer electrode. By changing the rise time of the discharge bias coil current and the geometrical structure of the shell, the magnetic field structure and its time evolution can be controlled. The effect of the copper shell has been numerically simulated for the actual gun structure, and experimentally confirmed. This may increase the magnetic helicity content results, through increased poloidal magnetic field.

  15. Magnetic Flux Compression in Plasmas

    Science.gov (United States)

    Velikovich, A. L.

    2012-10-01

    Magnetic flux compression (MFC) as a method for producing ultra-high pulsed magnetic fields had been originated in the 1950s by Sakharov et al. at Arzamas in the USSR (now VNIIEF, Russia) and by Fowler et al. at Los Alamos in the US. The highest magnetic field produced by explosively driven MFC generator, 28 MG, was reported by Boyko et al. of VNIIEF. The idea of using MFC to increase the magnetic field in a magnetically confined plasma to 3-10 MG, relaxing the strict requirements on the plasma density and Lawson time, gave rise to the research area known as MTF in the US and MAGO in Russia. To make a difference in ICF, a magnetic field of ˜100 MG should be generated via MFC by a plasma liner as a part of the capsule compression scenario on a laser or pulsed power facility. This approach was first suggested in mid-1980s by Liberman and Velikovich in the USSR and Felber in the US. It has not been obvious from the start that it could work at all, given that so many mechanisms exist for anomalously fast penetration of magnetic field through plasma. And yet, many experiments stimulated by this proposal since 1986, mostly using pulsed-power drivers, demonstrated reasonably good flux compression up to ˜42 MG, although diagnostics of magnetic fields of such magnitude in HED plasmas is still problematic. The new interest of MFC in plasmas emerged with the advancement of new drivers, diagnostic methods and simulation tools. Experiments on MFC in a deuterium plasma filling a cylindrical plastic liner imploded by OMEGA laser beam led by Knauer, Betti et al. at LLE produced peak fields of 36 MG. The novel MagLIF approach to low-cost, high-efficiency ICF pursued by Herrmann, Slutz, Vesey et al. at Sandia involves pulsed-power-driven MFC to a peak field of ˜130 MG in a DT plasma. A review of the progress, current status and future prospects of MFC in plasmas is presented.

  16. The effect of electron thermal conduction on plasma pressure gradient during reconnection of magnetic field lines

    Energy Technology Data Exchange (ETDEWEB)

    Chu, T.K.

    1987-12-01

    The interplay of electron cross-field thermal conduction and the reconnection of magnetic field lines around an m = 1 magnetic island prior to a sawtooth crash can generate a large pressure gradient in a boundary layer adjacent to the reconnecting surface, leading to an enhanced gradient of poloidal beta to satisfy the threshold condition for ideal MHD modes. This narrow boundary layer and the short onset time of a sawtooth crash can be supported by fine-grained turbulent processes in a tokamak plasma. 11 refs.

  17. Poloidal rotation driven by nonlinear momentum transport in strong electrostatic turbulence

    Science.gov (United States)

    Wang, Lu; Wen, Tiliang; Diamond, P. H.

    2016-10-01

    Virtually, all existing theoretical works on turbulent poloidal momentum transport are based on quasilinear theory. Nonlinear poloidal momentum flux— is universally neglected. However, in the strong turbulence regime where relative fluctuation amplitude is no longer small, quasilinear theory is invalid. This is true at the all-important plasma edge. In this work, nonlinear poloidal momentum flux in strong electrostatic turbulence is calculated using the Hasegawa-Mima equation, and is compared with quasilinear poloidal Reynolds stress. A novel property is that symmetry breaking in fluctuation spectrum is not necessary for a nonlinear poloidal momentum flux. This is fundamentally different from the quasilinear Reynold stress. Furthermore, the comparison implies that the poloidal rotation drive from the radial gradient of nonlinear momentum flux is comparable to that from the quasilinear Reynolds force. Nonlinear poloidal momentum transport in strong electrostatic turbulence is thus not negligible for poloidal rotation drive, and so may be significant to transport barrier formation.

  18. Multifield measurement of magnetic fluctuation-induced particle flux in a high-temperature toroidal plasma

    Science.gov (United States)

    Lin, L.; Ding, W. X.; Brower, D. L.

    2016-12-01

    Magnetic fluctuation-induced particle transport is explored in the high-temperature, high-beta interior of the Madison symmetric torus (MST) reversed-field pinch by performing a multifield measurement of the correlated product of magnetic and density fluctuations associated with global resistive tearing modes. Local density fluctuations are obtained by inverting the line-integrated interferometry data after resolving the mode helicity through correlation techniques. The local magnetic and current density fluctuations are then reconstructed using a parameterized fit of Faraday-effect polarimetry measurements. Reconstructed 2D images of density and current density perturbations in a poloidal cross section exhibit significantly different spatial structure. Combined with their relative phase, the magnetic-fluctuation-induced particle transport flux and its spatial distribution are resolved. The convective magnetic fluctuation-induced particle flux profile is measured for both standard and high-performance plasmas in MST with tokamak-like confinement, showing large reduction in the flux during improved confinement.

  19. Synchronization of Geodesic Acoustic Modes and Magnetic Fluctuations in Toroidal Plasmas

    Science.gov (United States)

    Zhao, K. J.; Nagashima, Y.; Diamond, P. H.; Dong, J. Q.; Itoh, K.; Itoh, S.-I.; Yan, L. W.; Cheng, J.; Fujisawa, A.; Inagaki, S.; Kosuga, Y.; Sasaki, M.; Wang, Z. X.; Wei, L.; Huang, Z. H.; Yu, D. L.; Hong, W. Y.; Li, Q.; Ji, X. Q.; Song, X. M.; Huang, Y.; Liu, Yi.; Yang, Q. W.; Ding, X. T.; Duan, X. R.

    2016-09-01

    The synchronization of geodesic acoustic modes (GAMs) and magnetic fluctuations is identified in the edge plasmas of the HL-2A tokamak. Mesoscale electric fluctuations (MSEFs) having components of a dominant GAM, and m /n =6 /2 potential fluctuations are found at the same frequency as that of the magnetic fluctuations of m /n =6 /2 (m and n are poloidal and toroidal mode numbers, respectively). The temporal evolutions of the MSEFs and the magnetic fluctuations clearly show the frequency entrainment and the phase lock between the GAM and the m /n =6 /2 magnetic fluctuations. The results indicate that GAMs and magnetic fluctuations can transfer energy through nonlinear synchronization. Such nonlinear synchronization may also contribute to low-frequency zonal flow formation, reduction of turbulence level, and thus confinement regime transitions.

  20. Efficient magnetic fields for supporting toroidal plasmas

    CERN Document Server

    Landreman, Matt

    2016-01-01

    The magnetic field that supports tokamak and stellarator plasmas must be produced by coils well separated from the plasma. However the larger the separation, the more difficult it is to produce a given magnetic field in the plasma region, so plasma configurations should be chosen that can be supported as efficiently as possible by distant coils. The properties of curl-free magnetic fields allow magnetic field distributions to be ranked in order of their difficulty of production from a distance. Plasma shapes with low curvature and spectral width may be difficult to support, whereas plasma shapes with sharp edges may be efficiently supported by distant coils. Two measures of difficulty, which correctly identify such differences in difficulty, will be examined. These measures, which can be expressed as matrices, relate the externally-produced normal magnetic field on the plasma surface to the either the normal field or current on a distant control surface. A singular value decomposition (SVD) of either matrix y...

  1. Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study

    Directory of Open Access Journals (Sweden)

    P. T. I. Eriksson

    2005-10-01

    Full Text Available Three ULF wave events, all occurring in the dayside magnetopshere during magnetically quiet times, are studied using the Cluster satellites. The multi-point measurements obtained from Cluster are used to determine the azimuthal wave number for the events by means of the phase shift and the azimuthal separation between the satellites. Also, the polarisation of the electric and magnetic fields is examined in a field-aligned coordinate system, which, in turn, gives the mode of the oscillations. The large-inclination orbits of Cluster allow us to examine the phase relationship between the electric and magnetic fields along the field lines. The events studied have large azimuthal wave numbers (m~100, two of them have eastward propagation and all are in the poloidal mode, consistent with the large wave numbers. We also use particle data from geosynchronous satellites to look for signatures of proton injections, but none of the events show any sign of enhanced proton flux. Thus, the drift-bounce resonance instability seems unlikely to have played any part in the excitation of these pulsations. As for the drift-mirror instability we conclude that it would require an unreasonably high plasma pressure for the instability criterion to be satisfied.

    Keywords. Ionosphere (Wave propagation – Magnetospheric physics (Plasma waves and instabilities; Instruments and techniques

  2. Magnetic stresses in ideal MHD plasmas

    DEFF Research Database (Denmark)

    Jensen, V.O.

    1995-01-01

    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......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...

  3. Dense magnetized plasma numerical simulations

    Energy Technology Data Exchange (ETDEWEB)

    Bilbao, L [INFIP-CONICET, and Physics Department (FCEN-UBA), Ciudad Universitaria, Pab. I, 1428 Buenos Aires (Argentina); Bernal, L, E-mail: bilbao@df.uba.a [Physics Department (FCEYN-UNMDP), Complejo Universitario, Funes y Pena, 7600 Mar del Plata (Argentina)

    2010-06-15

    The scope for developing the present numerical method was to perform parametric studies for optimization of several configurations in magnetized plasmas. Nowadays there exist several efficient numerical codes in the subject. However, the construction of one's own computational codes brings the following important advantages: (a) to get a deeper knowledge of the physical processes involved and the numerical methods used to simulate them and (b) more flexibility to adapt the code to particular situations in a more efficient way than would be possible for a closed general code. The code includes ion viscosity, thermal conduction (electrons and ions), magnetic diffusion, thermonuclear or chemical reaction, Bremsstrahlung radiation, and equation of state (from the ideal gas to the degenerate electron gas). After each calculation cycle, mesh vertices are moved arbitrarily over the fluid. The adaptive method consists of shifting mesh vertices over the fluid in order to keep a reasonable mesh structure and increase the spatial resolution where the physical solution demands. The code was a valuable tool for parametric study of different physical problems, mainly optimization of plasma focus machine, detonation and propagation of thermonuclear reactions and Kelvin-Helmholtz instabilities in the boundary layer of the terrestrial magnetopause.

  4. Analysis and modelling of the magnetic and plasma profiles during PPCD experiments in RFX

    Science.gov (United States)

    Puiatti, M. E.; Cappello, S.; Lorenzini, R.; Martini, S.; Ortolani, S.; Paccagnella, R.; Sattin, F.; Terranova, D.; Bolzonella, T.; Buffa, A.; Canton, A.; Carraro, L.; Escande, D. F.; Garzotti, L.; Innocente, P.; Marrelli, L.; Martines, E.; Scarin, P.; Spizzo, G.; Valisa, M.; Zanca, P.; Antoni, V.; Apolloni, L.; Bagatin, M.; Baker, W.; Barana, O.; Bettella, D.; Bettini, P.; Cavazzana, R.; Cavinato, M.; Chitarin, G.; Cravotta, A.; D'Angelo, F.; Dal Bello, S.; DeLorenzi, A.; Desideri, D.; Fiorentin, P.; Franz, P.; Frassinetti, L.; Gaio, E.; Giudicotti, L.; Gnesotto, F.; Grando, L.; Guo, S. C.; Luchetta, A.; Malesani, G.; Manduchi, G.; Marchiori, G.; Marcuzzi, D.; Martin, P.; Masiello, A.; Milani, F.; Moresco, M.; Murari, A.; Nielsen, P.; Pasqualotto, R.; Pégourie, B.; Peruzzo, S.; Piovan, R.; Piovesan, P.; Pomaro, N.; Preti, G.; Regnoli, G.; Rostagni, G.; Serianni, G.; Sonato, P.; Spada, E.; Spolaore, M.; Taliercio, C.; Telesca, G.; Toigo, V.; Vianello, N.; Zaccaria, P.; Zaniol, B.; Zanotto, L.; Zilli, E.; Zollino, G.; Zuin, M.

    2003-10-01

    In this paper, we analyse the main features of the pulsed poloidal current drive (PPCD) technique, used in the reversed field pinch configuration to achieve improved confinement conditions. In the RFX experiment, PPCD corresponds to a decrease of the magnetic fluctuations, to a peaking of the temperature profile, and to a reduced transport and plasma-wall interaction. A three-dimensional MHD nonlinear code and one-dimensional time-dependent transport models have been applied to study the effect of PPCD on the magnetic and plasma profiles. The three-dimensional MHD simulations show that the external inductive drive pinches and peaks the current profile driving the configuration through a transient phase, where the spontaneous turbulent dynamo action is quenched. The one-dimensional transport codes indicate that the experimental profile modifications associated with PPCD are consistent with a reduction of the stochastic transport.

  5. Magnetic topology and current channels in plasmas with toroidal current density inversions

    Science.gov (United States)

    Ciro, D.; Caldas, I. L.

    2013-10-01

    The equilibrium magnetic field inside axisymmetric plasmas with inversions on the toroidal current density is considered. Previous works have shown that internal regions with negative current density lead to non-nested magnetic surfaces inside the plasma. Following these results, we derive a general expression relating the positive and negative currents inside the non-nested surfaces. This is done in terms of an anisotropy parameter that is model-independent and is based in very general properties of the magnetic field. We demonstrate that the positive currents in axisymmetric islands screen the negative one in the plasma center by reaching about twice its magnitude. Further, we illustrate these results by developing a family of analytical local solutions for the poloidal magnetic field in a region of interest that contains the inverted current. These local solutions exhibit non-nested magnetic surfaces with a combined current of at least twice the magnitude of the negative one, as prescribed from the topological arguments, and allow to study topological transitions driven by geometrical changes in the current profile. To conclude, we discuss the signatures of internal current density inversions in a confinement device and show that magnetic pitch measurements may be inappropriate to differentiate current reversals and small current holes in plasmas.

  6. Magnetized Plasma Experiments Using Thermionic- Thermoelectronic Plasma Emitter

    Science.gov (United States)

    Kawamori, Eiichirou; Cheng, C. Z.; Fujikawa, Nobuko; Lee, Jyun-Yi; Peng, Albert

    2008-11-01

    We are developing a magnetic mirror device, which is the first magnetized plasma device in Taiwan, to explore basic plasma sciences relevant to fusion, space and astrophysical plasmas. Our research subjects include electromagnetically induced transparency (EIT), Alfven wave physics, and plasma turbulence. A large diameter (> 200 mm) plasma emitter1, which utilizes thermionic- thermoelectronic emission from a mixture of LaB6 (Lanthanum-hexaboride) and beta-eucryptite (lithium type aluminosylicate) powders, is employed as a plasma source because of its production ability of fully ionized plasma and controllability of plasma emission rate. The plasma emitter has been installed recently and investigation of its characteristics will be started. The employment of beta-eucryptite in plasma emitter is the first experimental test because such investigation of beta-eucryptite has previously been used only for Li+-ion source2. Our plan for magnetized plasma experiments and results of the plasma emitter investigation will be presented. 1. K. Saeki, S. Iizuka, N. Sato, and Y. Hatta, Appl. Phys. Lett., 37, 1980, pp. 37-38. 2. M. Ueda, R. R. Silva, R. M. Oliveira, H. Iguchi, J. Fujita and K. Kadota, J. Phys. D: Appl. Phys. 30 1997, pp. 2711--2716.

  7. An improved neoclassical drift-magnetohydrodynamical fluid model of helical magnetic island equilibria in tokamak plasmas

    Science.gov (United States)

    Fitzpatrick, Richard

    2016-05-01

    The effect of the perturbed ion polarization current on the stability of neoclassical tearing modes in tokamak plasmas is calculated using an improved, neoclassical, four-field, drift-magnetohydrodynamical model. The calculation involves the self-consistent determination of the pressure and scalar electric potential profiles in the vicinity of the associated magnetic island chain, which allows the chain's propagation velocity to be fixed. Two regimes are considered. First, a regime in which neoclassical ion poloidal flow damping is not strong enough to enhance the magnitude of the polarization current (relative to that found in slab geometry). Second, a regime in which neoclassical ion poloidal flow damping is strong enough to significantly enhance the magnitude of the polarization current. In both regimes, two types of solution are considered. First, a freely rotating solution (i.e., an island chain that is not interacting with a static, resonant, magnetic perturbation). Second, a locked solution (i.e., an island chain that has been brought to rest in the laboratory frame via interaction with a static, resonant, magnetic perturbation). In all cases, the polarization current is found to be either always stabilizing or stabilizing provided that ηi≡d ln Ti/d ln ne does not exceed some threshold value. In certain ranges of ηi, the polarization current is found to have a stabilizing effect on a freely rotating island, but a destabilizing effect on a corresponding locked island.

  8. Magnetic field penetration of erosion switch plasmas

    Science.gov (United States)

    Mason, Rodney J.; Jones, Michael E.; Grossmann, John M.; Ottinger, Paul F.

    1988-10-01

    Computer simulations demonstrate that the entrainment (or advection) of magnetic field with the flow of cathode-emitted electrons can constitute a dominant mechanism for the magnetic field penetration of erosion switch plasmas. Cross-field drift in the accelerating electric field near the cathode starts the penetration process. Plasma erosion propagates the point for emission and magnetic field injection along the cathode toward the load-for the possibility of rapid switch opening.

  9. Poloidal rotation driven by nonlinear momentum transport in strong electrostatic turbulence

    CERN Document Server

    Wang, Lu; Diamond, P H

    2016-01-01

    Virtually, all existing theoretical works on turbulent poloidal momentum transport are based on quasilinear theory. Nonlinear poloidal momentum flux - $\\langle \\tilde{v}_r \\tilde{n} \\tilde{v}_{\\theta} \\rangle$ is universally neglected. However, in the strong turbulence regime where relative fluctuation amplitude is no longer small, quasilinear theory is invalid. This is true at the all-important plasma edge. In this work, nonlinear poloidal momentum flux $ \\langle \\tilde{v}_r \\tilde{n} \\tilde{v}_{\\theta} \\rangle $ in strong electrostatic turbulence is calculated using Hasegawa-Mima equation, and is compared with quasilinear poloidal Reynolds stress. A novel property is that symmetry breaking in fluctuation spectrum is not necessary for a nonlinear poloidal momentum flux. This is fundamentally different from the quasilinear Reynold stress. Furthermore, the comparison implies that the poloidal rotation drive from the radial gradient of nonlinear momentum flux is comparable to that from the quasilinear Reynolds ...

  10. Analytic expression for poloidal flow velocity in the banana regime

    Energy Technology Data Exchange (ETDEWEB)

    Taguchi, M. [College of Industrial Technology, Nihon University, Narashino 275-8576 (Japan)

    2013-01-15

    The poloidal flow velocity in the banana regime is calculated by improving the l = 1 approximation for the Fokker-Planck collision operator [M. Taguchi, Plasma Phys. Controlled Fusion 30, 1897 (1988)]. The obtained analytic expression for this flow, which can be used for general axisymmetric toroidal plasmas, agrees quite well with the recently calculated numerical results by Parker and Catto [Plasma Phys. Controlled Fusion 54, 085011 (2012)] in the full range of aspect ratio.

  11. Magnetic field of a combined plasma trap

    Science.gov (United States)

    Kotenko, V. G.; Moiseenko, V. E.; Ågren, O.

    2012-06-01

    This paper presents numerical simulations performed on the structure of a magnetic field created by the magnetic system of a combined plasma trap. The magnetic system includes the stellarator-type magnetic system and one of the mirror-type. For the stellarator type magnetic system the numeric model contains a magnetic system of an l=2 torsatron with the coils of an additional toroidal magnetic field. The mirror-type magnetic system element is considered as being single current-carrying turn enveloping the region of existence of closed magnetic surfaces of the torsatron. The calculations indicate the existence of a vast area of the values of the additional magnetic field magnitude and magnetic field of the single turn where, in principle, the implementation of the closed magnetic surface configuration is quite feasible.

  12. Poloidal radiation asymmetries during disruption mitigation by massive gas injection on the DIII-D tokamak

    Science.gov (United States)

    Eidietis, N. W.; Izzo, V. A.; Commaux, N.; Hollmann, E. M.; Shiraki, D.

    2017-10-01

    A comparison of radiated power poloidal peaking during disruption mitigation using massive gas injection at multiple poloidal positions on the DIII-D tokamak is presented. The two injectors are located poloidally above and below the low field side midplane and toroidally located within the quadrants to either side of the fast bolometry diagnostic used to measure the radiated power. Differing quantities of injected neon are compared. A strong dependence of impurity poloidal flows upon the injector location is observed. Injection from the upper half of the vessel results in strong poloidal flows over the top of the plasma to the high field side midplane, while lower injection exhibits far less pronounced poloidal flow that is oriented in the opposite direction. The poloidal location of both pre-thermal quench and thermal quench emissivity peaking shows a strong dependence upon the injector location, although the poloidal flow in the upper injection case results in a much broader distribution. The wall radiative heat flux mimics the emissivity, but the distribution is smoothed with lower poloidal peaking due to geometric effects. Thermal quench MHD appears to have little effect upon the poloidal phase of maximum emissivity in experiment or modeling, which can be attributed to the slower parallel transport of impurities along field lines in the poloidal versus toroidal direction. Poloidal peaking factors of ≤1.6 and ≤2.2 were observed for upper and lower injection, respectively. Under very conservative assumptions, the observed poloidal peaking factor will bring ITER near the melting limit for first wall stainless steel. However, further modeling is required to determine if those conservative assumptions are warranted.

  13. 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

  14. Magnetic circuit for hall effect plasma accelerator

    Science.gov (United States)

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

    2009-01-01

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

  15. Magnetizing a complex plasma without a magnetic field

    CERN Document Server

    Kählert, H; Bonitz, M; Löwen, H; Greiner, F; Piel, A

    2012-01-01

    We propose and demonstrate a concept that mimics the magnetization of the heavy dust particles in a complex plasma while leaving the properties of the light species practically unaffected. It makes use of the frictional coupling between a complex plasma and the neutral gas, which allows to transfer angular momentum from a rotating gas column to a well-controlled rotation of the dust cloud. This induces a Coriolis force that acts exactly as the Lorentz force in a magnetic field. Experimental normal mode measurements for a small dust cluster with four particles show excellent agreement with theoretical predictions for a magnetized plasma.

  16. Magnetic field amplification in turbulent astrophysical plasmas

    CERN Document Server

    Federrath, Christoph

    2016-01-01

    Magnetic fields play an important role in astrophysical accretion discs, and in the interstellar and intergalactic medium. They drive jets, suppress fragmentation in star-forming clouds and can have a significant impact on the accretion rate of stars. However, the exact amplification mechanisms of cosmic magnetic fields remain relatively poorly understood. Here I start by reviewing recent advances in the numerical and theoretical modelling of the 'turbulent dynamo', which may explain the origin of galactic and inter-galactic magnetic fields. While dynamo action was previously investigated in great detail for incompressible plasmas, I here place particular emphasis on highly compressible astrophysical plasmas, which are characterised by strong density fluctuations and shocks, such as the interstellar medium. I find that dynamo action works not only in subsonic plasmas, but also in highly supersonic, compressible plasmas, as well as for low and high magnetic Prandtl numbers. I further present new numerical simu...

  17. Effects of resistivity on linear plasma responses to resonant magnetic perturbations in tokamak plasmas

    Science.gov (United States)

    Kim, Juhyung; Kim, S. S.; Jhang, Hogun

    2016-09-01

    Numerical studies are made of the effects of resistivity on linear plasma responses to resonant magnetic perturbations (RMPs) in tokamaks based on a reduced magnetohydrodynamic model. From a local two-field model, it is suggested that the ratio of the poloidal electron advection to the resistivity diffusion rate α m can be a figure of merit parameter in linear RMP penetration physics. The shielding efficiency is governed by α m , and when α m ≳ 1 , RMPs are effectively shielded. Global simulations using a four-field model [Hazeltine and Meiss, Phys. Rep. 121, 1 (1985)] show that there exists an effective threshold of the perpendicular electron flow ( Ve , ⊥ c ) beyond which RMPs cannot penetrate. Resistivity is found to determine Ve , ⊥ c which increases as resistivity becomes higher, making RMP penetration easier. At low resistivity, small Ve , ⊥ c renders the RMP penetration sensitive to ion collisionality and the change in q95. The kink response is observed to be closely related to the residual level of RMPs at rational surfaces and can be also strongly affected by resistivity.

  18. Nonlinear Electrostatic Wave Equations for Magnetized Plasmas

    DEFF Research Database (Denmark)

    Dysthe, K.B.; Mjølhus, E.; Pécseli, Hans

    1984-01-01

    The lowest order kinetic effects are included in the equations for nonlinear electrostatic electron waves in a magnetized plasma. The modifications of the authors' previous analysis based on a fluid model are discussed.......The lowest order kinetic effects are included in the equations for nonlinear electrostatic electron waves in a magnetized plasma. The modifications of the authors' previous analysis based on a fluid model are discussed....

  19. Plasmon Weyl Degeneracies in Magnetized Plasma

    CERN Document Server

    Gao, Wenlong; Lawrence, Mark; Fang, Fengzhou; Béri, Benjamin; Zhang, Shuang

    2015-01-01

    In this letter, we report the presence of novel type of plasmon Weyl points in a naturally existing material - magnetized plasma. In such a medium, conventional, purely longitudinal bulk plasma oscillations exists only along the direction of applied magnetic field (z direction). With strong enough magnetic field, there exist helical propagating modes along z direction with circular polarizations. The orthogonality between the longitudinal bulk plasmon mode and the transverse helical propagating modes guarantees their crossing at the bulk plasmon frequency. These crossing points, embedded in the bulk plasmon dispersion line, serve as monopoles in the k space - the so called Weyl points. These Weyl points lead to salient observable features. These include the highly intriguing observation that, at a magnetized plasma surface which is parallel to the applied magnetic field, reflection of an electromagnetic wave with in-plane wave-vector close to the Weyl points exhibits chiral behavior only in half of the k plan...

  20. Microwave Reflectometry for Magnetically Confined Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Mazzucato, E.

    1998-02-01

    This paper is about microwave reflectometry -- a radar technique for plasma density measurements using the reflection of electromagnetic waves by a plasma cutoff. Both the theoretical foundations of reflectometry and its practical application to the study of magnetically confined plasmas are reviewed in this paper. In particular, the role of short-scale density fluctuations is discussed at length, both as a unique diagnostic tool for turbulence studies in thermonuclear plasmas and for the deleterious effects that fluctuations may have on the measurement of the average plasma density with microwave reflectometry.

  1. Magnetic Flux Compression Experiments Using Plasma Armatures

    Science.gov (United States)

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

    2003-01-01

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

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

    Science.gov (United States)

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

    2016-10-01

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

  3. Collisionless Coupling between Explosive Debris Plasma and Magnetized Ambient Plasma

    Science.gov (United States)

    Bondarenko, Anton

    2016-10-01

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

  4. Plasma transport in the Scrape-off-Layer of magnetically confined plasma and the plasma exhaust

    DEFF Research Database (Denmark)

    Rasmussen, Jens Juul; Naulin, Volker; Nielsen, Anders Henry

    An overview of the plasma dynamics in the Scrape-off-Layer (SOL) of magnetically confined plasma is presented. The SOL is the exhaust channel of the warm plasma from the core, and the understanding of the SOL plasma dynamics is one of the key issues in contemporary fusion research. It is essential...

  5. Magnetic reconnection between colliding magnetized laser-produced plasma plumes.

    Science.gov (United States)

    Fiksel, G; Fox, W; Bhattacharjee, A; Barnak, D H; Chang, P-Y; Germaschewski, K; Hu, S X; Nilson, P M

    2014-09-05

    Observations of magnetic reconnection between colliding plumes of magnetized laser-produced plasma are presented. Two counterpropagating plasma flows are created by irradiating oppositely placed plastic (CH) targets with 1.8-kJ, 2-ns laser beams on the Omega EP Laser System. The interaction region between the plumes is prefilled with a low-density background plasma and magnetized by an externally applied magnetic field, imposed perpendicular to the plasma flow, and initialized with an X-type null point geometry with B=0 at the midplane and B=8  T at the targets. The counterflowing plumes sweep up and compress the background plasma and the magnetic field into a pair of magnetized ribbons, which collide, stagnate, and reconnect at the midplane, allowing the first detailed observations of a stretched current sheet in laser-driven reconnection experiments. The dynamics of current sheet formation are in good agreement with first-principles particle-in-cell simulations that model the experiments.

  6. Blob dynamics in TORPEX poloidal null configurations

    Science.gov (United States)

    Shanahan, B. W.; Dudson, B. D.

    2016-12-01

    3D blob dynamics are simulated in X-point magnetic configurations in the TORPEX device via a non-field-aligned coordinate system, using an isothermal model which evolves density, vorticity, parallel velocity and parallel current density. By modifying the parallel gradient operator to include perpendicular perturbations from poloidal field coils, numerical singularities associated with field aligned coordinates are avoided. A comparison with a previously developed analytical model (Avino 2016 Phys. Rev. Lett. 116 105001) is performed and an agreement is found with minimal modification. Experimental comparison determines that the null region can cause an acceleration of filaments due to increasing connection length, but this acceleration is small relative to other effects, which we quantify. Experimental measurements (Avino 2016 Phys. Rev. Lett. 116 105001) are reproduced, and the dominant acceleration mechanism is identified as that of a developing dipole in a moving background. Contributions from increasing connection length close to the null point are a small correction.

  7. Integrity of the Plasma Magnetic Nozzle

    Science.gov (United States)

    Gerwin, Richard A.

    2009-01-01

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

  8. Magnetic curvature effects on plasma interchange turbulence

    Science.gov (United States)

    Li, B.; Liao, X.; Sun, C. K.; Ou, W.; Liu, D.; Gui, G.; Wang, X. G.

    2016-06-01

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

  9. Multi-scale interaction between magnetic islands and microturbulence in magnetized plasmas; Modelisation et simulation de l'interaction multi-echelle entre ilots magnetiques et la microturbulence dans les plasmas de fusion magnetises

    Energy Technology Data Exchange (ETDEWEB)

    Muraglia, M.

    2009-10-15

    In a tokamak, it exists many kinds of instability at the origin of a damage of the confinement and worst of a lost of a confinement. This work presents a study of the dynamics of a magnetic island in presence of turbulence in magnetized plasmas. More precisely, the goal is to understand the multi-scales interaction between turbulence, generated by a pressure gradient and the magnetic field curvature, and a magnetic island formed thanks to a tearing mode. Thanks to the derivation of a 2-dimensional slab model taking into account both tearing and interchange instabilities, theoretical and numerical linear studies show the pressure effect on the magnetic island linear formation and show interchange modes are stabilized in presence of a strong magnetic field. Then, a numerical nonlinear study is presented in order to understand how the interchange mechanism affects the nonlinear dynamics of a magnetic island. It is shown that the pressure gradient and the magnetic field curvature affect strongly the nonlinear evolution of a magnetic island through dynamics bifurcations. The nature of these bifurcations should be characterized in function of the linear situation. Finally, the last part of this work is devoted to the study of the origin of the nonlinear poloidal rotation of the magnetic island. A model giving the different contributions to the rotation is derived. It is shown, thanks to the model and to the numerical studies, that the nonlinear rotation of the island is mainly governed by the ExB poloidal flow and/or by the nonlinear diamagnetic drift. (author)

  10. Transient Growth in a Magnetized Vlasov Plasma

    Science.gov (United States)

    Ratushnaya, Valeria; Samtaney, Ravi

    2015-11-01

    Collisionless plasmas, such as those encountered in tokamaks, exhibit a rich variety of instabilities. The physical origin, triggering mechanisms and fundamental understanding of many tokamak instabilities, however, is still an open problem. Aiming to gain a better insight into this question, we investigate the stability properties of a collisionless Vlasov plasma for the case of: (a) stationary homogeneous magnetic field, and (b) weakly non-stationary and non-homogeneous magnetic field. We narrow the scope of our investigation to the case of a Maxwellian plasma and examine its evolution with an electrostatic approximation. We show that the linearized Vlasov operator is non-normal, which leads to an algebraic growth of perturbations in a magnetized plasma followed by exponential decay, i.e., classical Landau damping behaviour. This is a so-called transient growth phenomenon, developed in the framework of non-modal stability theory in the context of hydrodynamics. In a homogeneous magnetic field the typical time scales of the transient growth are of the order of several plasma periods. The first-order distribution function and the corresponding electric field are calculated and the dependence on the initial conditions is studied. Supported by baseline research funds at KAUST.

  11. Current filaments in turbulent magnetized plasmas

    DEFF Research Database (Denmark)

    Martines, E.; Vianello, N.; Sundkvist, D.;

    2009-01-01

    Direct measurements of current density perturbations associated with non-linear phenomena in magnetized plasmas can be carried out using in situ magnetic measurements. In this paper we report such measurements for three different kinds of phenomena. Current density fluctuations in the edge density...... gradient region of a fusion plasma confined in reversed field pinch configuration and in a density gradient region in the Earth magnetosphere are measured and compared, showing that in both environments they can be attributed to drift-Alfvén vortices. Current structures associated with reconnection events...

  12. Exchange effects in magnetized quantum plasmas

    CERN Document Server

    Trukhanova, Mariya Iv

    2015-01-01

    We apply the many-particle quantum hydrodynamics including the Coulomb exchange interaction to magnetized quantum plasmas. We consider a number of wave phenomenon under influence of the Coulomb exchange interaction. Since the Coulomb exchange interaction affects longitudinal and transverse-longitudinal waves we focus our attention to the Langmuir waves, Trivelpiece-Gould waves, ion-acoustic waves in non-isothermal magnetized plasmas, the dispersion of the longitudinal low-frequency ion-acoustic waves and low-frequencies electromagnetic waves at $T_{e}\\gg T_{i}$ . We obtained the numerical simulation of the dispersion properties of different types of waves.

  13. Nonlinear Electron Waves in Strongly Magnetized Plasmas

    DEFF Research Database (Denmark)

    Pécseli, Hans; Juul Rasmussen, Jens

    1980-01-01

    dynamics in the analysis is also demonstrated. As a particular case the authors investigate nonlinear waves in a strongly magnetized plasma filled wave-guide, where the effects of finite geometry are important. The relevance of this problem to laboratory experiments is discussed.......Weakly nonlinear dispersive electron waves in strongly magnetized plasma are considered. A modified nonlinear Schrodinger equation is derived taking into account the effect of particles resonating with the group velocity of the waves (nonlinear Landau damping). The possibility of including the ion...

  14. Scaling laws in magnetized plasma turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Boldyrev, Stanislav [Univ. of Wisconsin, Madison, WI (United States)

    2015-06-28

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

  15. Compressional plasma flows near magnetic null points

    Energy Technology Data Exchange (ETDEWEB)

    Bulanov, S.V.; Ol' shanetskii, M.A.

    1985-06-01

    Self-similar solutions of the MHD equations describing time-varying plasma flows near magnetic null points are analyzed. Various classes of particular solutions are constructed. Special attention is paid to compressional flows which involve the development of sharp maxima. The stability of the self-similar solutions is studied. Solutions describing the motion of a vortex in MHD are constructed. The possibility of producing current sheets in nonuniform magnetic configurations is demonstrated.

  16. Optimization of applied non-axisymmetric magnetic perturbations using multimodal plasma response on DIII-D

    Science.gov (United States)

    Weisberg, D. B.; Paz-Soldan, C.; Lanctot, M. J.; Strait, E. J.; Evans, T. E.

    2016-10-01

    The plasma response to proposed 3D coil geometries in the DIII-D tokamak is investigated using the linear MHD plasma response code MARS-F. An extensive examination of low- and high-field side coil arrangements shows the potential to optimize the coupling between imposed non-axisymmetric magnetic perturbations and the total plasma response by varying the toroidal and poloidal spectral content of the applied field. Previous work has shown that n=2 and n=3 perturbations can suppress edge-localized modes (ELMs) in cases where the applied field's coupling to resonant surfaces is enhanced by amplifying marginally-stable kink modes. This research is extended to higher n-number configurations of 2 to 3 rows with up to 12 coils each in order to advance the physical understanding and optimization of both the resonant and non-resonant responses. Both in- and ex-vessel configurations are considered. The plasma braking torque is also analyzed, and coil geometries with favorable plasma coupling characteristics are discussed. Work supported by GA internal funds.

  17. Non-linear magnetohydrodynamic modeling of plasma response to resonant magnetic perturbations

    Energy Technology Data Exchange (ETDEWEB)

    Orain, F.; Bécoulet, M.; Dif-Pradalier, G.; Nardon, E.; Passeron, C.; Latu, G.; Grandgirard, V.; Fil, A.; Ratnani, A. [CEA, IRFM, F-13108 Saint-Paul-Lez-Durance (France); Huijsmans, G. [ITER Organization, Route de Vinon, F-13115 Saint-Paul-Lez-Durance (France); Pamela, S. [IIFS-PIIM. Aix Marseille Université - CNRS, 13397 Marseille Cedex20 (France); Chapman, I.; Kirk, A.; Thornton, A. [EURATOM/CCFE Fusion Association, Culham Science Centre, Oxon OX14 3DB (United Kingdom); Hoelzl, M. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching (Germany); Cahyna, P. [Association EURATOM/IPP.CR, Prague (Czech Republic)

    2013-10-15

    The interaction of static Resonant Magnetic Perturbations (RMPs) with the plasma flows is modeled in toroidal geometry, using the non-linear resistive MHD code JOREK, which includes the X-point and the scrape-off-layer. Two-fluid diamagnetic effects, the neoclassical poloidal friction and a source of toroidal rotation are introduced in the model to describe realistic plasma flows. RMP penetration is studied taking self-consistently into account the effects of these flows and the radial electric field evolution. JET-like, MAST, and ITER parameters are used in modeling. For JET-like parameters, three regimes of plasma response are found depending on the plasma resistivity and the diamagnetic rotation: at high resistivity and slow rotation, the islands generated by the RMPs at the edge resonant surfaces rotate in the ion diamagnetic direction and their size oscillates. At faster rotation, the generated islands are static and are more screened by the plasma. An intermediate regime with static islands which slightly oscillate is found at lower resistivity. In ITER simulations, the RMPs generate static islands, which forms an ergodic layer at the very edge (ψ≥0.96) characterized by lobe structures near the X-point and results in a small strike point splitting on the divertor targets. In MAST Double Null Divertor geometry, lobes are also found near the X-point and the 3D-deformation of the density and temperature profiles is observed.

  18. Non-linear magnetohydrodynamic modeling of plasma response to resonant magnetic perturbations

    Science.gov (United States)

    Orain, F.; Bécoulet, M.; Dif-Pradalier, G.; Huijsmans, G.; Pamela, S.; Nardon, E.; Passeron, C.; Latu, G.; Grandgirard, V.; Fil, A.; Ratnani, A.; Chapman, I.; Kirk, A.; Thornton, A.; Hoelzl, M.; Cahyna, P.

    2013-10-01

    The interaction of static Resonant Magnetic Perturbations (RMPs) with the plasma flows is modeled in toroidal geometry, using the non-linear resistive MHD code JOREK, which includes the X-point and the scrape-off-layer. Two-fluid diamagnetic effects, the neoclassical poloidal friction and a source of toroidal rotation are introduced in the model to describe realistic plasma flows. RMP penetration is studied taking self-consistently into account the effects of these flows and the radial electric field evolution. JET-like, MAST, and ITER parameters are used in modeling. For JET-like parameters, three regimes of plasma response are found depending on the plasma resistivity and the diamagnetic rotation: at high resistivity and slow rotation, the islands generated by the RMPs at the edge resonant surfaces rotate in the ion diamagnetic direction and their size oscillates. At faster rotation, the generated islands are static and are more screened by the plasma. An intermediate regime with static islands which slightly oscillate is found at lower resistivity. In ITER simulations, the RMPs generate static islands, which forms an ergodic layer at the very edge (ψ ≥0.96) characterized by lobe structures near the X-point and results in a small strike point splitting on the divertor targets. In MAST Double Null Divertor geometry, lobes are also found near the X-point and the 3D-deformation of the density and temperature profiles is observed.

  19. Dynamics of Exploding Plasma Within a Magnetized Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Dimonte, G; Dipeso, G; Hewett, D

    2002-02-01

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

  20. Magnetized Target Fusion Driven by Plasma Liners

    Science.gov (United States)

    Thio, Y. C. Francis; Cassibry, Jason; Eskridge, Richard; Kirkpatrick, Ronald C.; Knapp, Charles E.; Lee, Michael; Martin, Adam; Smith, James; Wu, S. T.; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    For practical applications of magnetized target fusion, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Quasi-spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a quasi-spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC). Theoretical analysis and computer modeling of the concept are presented. It is shown that, with the appropriate choice of the flow parameters in the liner and the target, the impact between the liner and the target plasma can be made to be shockless in the liner or to generate at most a very weak shock in the liner. Additional information is contained in the original extended abstract.

  1. Langmuir Solitons in Magnetized Plasmas

    DEFF Research Database (Denmark)

    Dysthe, K. B.; Mjølhus, E.; Pécseli, Hans;

    1978-01-01

    The authors have considered the nonlinear interaction between a high frequency (Langmuir) wave, which propagates at an arbitrary angle to a weak, constant magnetic field, and low frequency (ion-cyclotron or ion-sound) perturbations. In studying Langmuir envelope solitons they have unified...

  2. Plasma Pressure Driven Magnetic Self-Focusing of Aspherical Supernovae and Highly Collimated Gamma-Ray Bursts

    CERN Document Server

    Tsui, K H

    2012-01-01

    During the process of core-collapse of a massive star, the iron core evolves into an inner central core and an outer envelope, generating a cavity in between. The dynamics of this cavity, filled with plasma and magnetic field by the rapidly rotating pulsar (spun-down magnetar) at the center, is believed to be very relevant to account for supernovae and gamma-ray bursts \\citep{uzdensky2007}. The interactions of the pressurized conducting plasma and the magnetic field could generate some spatial distributions of plasma and magnetic field within the cavity. In an effort to better understand the spatial distributions, a set of time-dependent magnetohydrodynamic (MHD) equations is used to model this cavity system. Homologous solutions in Lagrangian representation are obtained to account for the spatial structures. Under this self-similar description, the magnetic flux function is governed by an eigenvalue equation with the eigenvalue being the poloidal plasma $\\beta$, which is the ratio of plasma pressure to poloi...

  3. Transparency of Magnetized Plasma at Cyclotron Frequency

    Energy Technology Data Exchange (ETDEWEB)

    G. Shvets; J.S. Wurtele

    2002-03-14

    Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of the three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of the nonlocal plasma oscillation. The complexity of the plasma system results in an index of refraction at the cyclotron frequency that differs from unity. Lagrangian description was used to elucidate the physics and enable numerical simulation of the plasma transparency and control of group and phase velocity. This control naturally leads to applications for electromagnetic pulse compression in the plasma and electron/ion acceleration.

  4. Long-Range Collisions in Magnetized Plasmas

    Science.gov (United States)

    Dubin, D.

    2015-12-01

    Astrophysical (and earthbound) plasmas in strong magnetic fields exhibit collisional effects that are not described by classical collision theory nor by the standard collision operators, such as the Landau or Balescu-Lenard operators. These theories implicitly neglect "long-range" collisions, i.e. collisions with impact parameters large compared to the cyclotron radius. This presentation will review several important physical effects such collisions have on various phenomena, including cross-magnetic field diffusion, heat conduction, and collisional slowing parallel to the magnetic field. Long-range collisions are analyzed as guiding-centers moving in one-dimension along the magnetic field, with parallel energy and momentum transferred to particles on separate field lines through the screened Coulomb interaction. This causes cross-field heat transport that is independent of magnetic field strength B (as opposed to the classical 1/B2 scaling), and enhances the rate of collisional slowing parallel to B. The Coulomb interaction between guiding centers on different field lines also produces random ExB drifts that enhance cross-magnetic field diffusion compared to the classical theory. The theory of long-range guiding center collisions must also include the novel effect of "collisional caging": plasma noise causes two colliding guiding centers to diffuse in relative parallel velocity, reversing their motion along B and colliding several times before becoming uncorrelated. This further enhances cross-field diffusion from long-range collisions by a factor of three, and enhances parallel slowing by a factor of approximately 1.5.

  5. Magnetized Plasma Compression for Fusion Energy

    Science.gov (United States)

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

    2013-10-01

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

  6. Magnetic compression of an FRC plasma

    Energy Technology Data Exchange (ETDEWEB)

    Okada, S.; Kitano, K.; Matsumoto, H. [Plasma Physics Laboratory, Faculty of Engineering, Osaka Univ., Suita, Osaka (JP)] [and others

    1999-04-01

    Confinement of a plasma with field-reversed configuration (FRC) is predicted to be improved if it is compressed only axially, keeping the magnetic flux between the separatrix and the confining chamber (flux conserver) wall unchanged, while allowing the plasma to expand radially. The prediction is based on an empirical scaling law of FRC confinement and on the assumption that the compression is done adiabatically. The apparatus for this axial compression was developed and the axial compression experiment was actually carried out by decreasing the distance of the mirror fields between which the FRC plasma is confined by 30% and the plasma life time of about 500 {mu}s was increased by about 50 {mu}s. (author)

  7. ARE TORNADO-LIKE MAGNETIC STRUCTURES ABLE TO SUPPORT SOLAR PROMINENCE PLASMA?

    Energy Technology Data Exchange (ETDEWEB)

    Luna, M.; Moreno-Insertis, F. [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Priest, E. [Mathematics Institute, University of St Andrews, St Andrews KY16 9SS (United Kingdom)

    2015-07-20

    Recent high-resolution and high-cadence observations have surprisingly suggested that prominence barbs exhibit apparent rotating motions suggestive of a tornado-like structure. Additional evidence has been provided by Doppler measurements. The observations reveal opposite velocities for both hot and cool plasma on the two sides of a prominence barb. This motion is persistent for several hours and has been interpreted in terms of rotational motion of prominence feet. Several authors suggest that such barb motions are rotating helical structures around a vertical axis similar to tornadoes on Earth. One of the difficulties of such a proposal is how to support cool prominence plasma in almost-vertical structures against gravity. In this work we model analytically a tornado-like structure and try to determine possible mechanisms to support the prominence plasma. We have found that the Lorentz force can indeed support the barb plasma provided the magnetic structure is sufficiently twisted and/or significant poloidal flows are present.

  8. Magnetic loop generation by collisionless gravitationally bound plasmas in axisymmetric tori.

    Science.gov (United States)

    Cremaschini, Claudio; Stuchlík, Zdeněk

    2013-04-01

    Current-carrying string loops are adopted in astrophysics to model the dynamics of isolated flux tubes of magnetized plasma expected to arise in the gravitational field of compact objects, such as black holes. Recent studies suggest that they could provide a framework for the acceleration and collimation of jets of plasma observed in these systems. However, the problem remains of the search of physical mechanisms which can consistently explain the occurrence of such plasma toroidal structures characterized by nonvanishing charge currents and are able to self-generate magnetic loops. In this paper, the problem is addressed in the context of Vlasov-Maxwell theory for nonrelativistic collisionless plasmas subject to both gravitational and electromagnetic fields. A kinetic treatment of quasistationary axisymmetric configurations of charged particles exhibiting epicyclic motion is obtained. Explicit solutions for the species equilibrium phase-space distribution function are provided. These are shown to have generally a non-Maxwellian character and to be characterized by nonuniform fluid fields and temperature anisotropy. Calculation of the relevant fluid fields and analysis of the Ampere equation then show the existence of nonvanishing current densities. As a consequence, the occurrence of a kinetic dynamo is proved, which can explain the self-generation of both azimuthal and poloidal magnetic fields by the plasma itself. This mechanism can operate in the absence of instabilities, turbulence, or accretion phenomena and is intrinsically kinetic in character. In particular, several kinetic effects contribute to it, identified here with finite Larmor radius, diamagnetic and energy-correction effects together with temperature anisotropy, and non-Maxwellian features of the equilibrium distribution function.

  9. Axisymmetric equilibria of a gravitating plasma with incompressible flows

    CERN Document Server

    Throumoulopoulos, G N

    2001-01-01

    It is found that the ideal magnetohydrodynamic equilibrium of an axisymmetric gravitating magnetically confined plasma with incompressible flows is governed by a second-order elliptic differential equation for the poloidal magnetic flux function containing five flux functions coupled with a Poisson equation for the gravitation potential, and an algebraic relation for the pressure. This set of equations is amenable to analytic solutions. As an application, the magnetic-dipole static axisymmetric equilibria with vanishing poloidal plasma currents derived recently by Krasheninnikov, Catto, and Hazeltine [Phys. Rev. Lett. {\\bf 82}, 2689 (1999)] are extended to plasmas with finite poloidal currents, subject to gravitating forces from a massive body (a star or black hole) and inertial forces due to incompressible sheared flows. Explicit solutions are obtained in two regimes: (a) in the low-energy regime $\\beta_0\\approx \\gamma_0\\approx \\delta_0 \\approx\\epsilon_0\\ll 1$, where $\\beta_0$, $\\gamma_0$, $\\delta_0$, and $\\...

  10. From Poloidal to Toroidal: Detection of Well-ordered Magnetic Field in High-mass Proto-cluster G35.2-0.74N

    CERN Document Server

    Qiu, Keping; Menten, Karl M; Liu, Hauyu B; Tang, Ya-Wen

    2013-01-01

    We report on detection of an ordered magnetic field (B field) threading a massive star-forming clump in the molecular cloud G35.2-0.74, using Submillimeter Array observations of polarized dust emission. Thanks to the sensitive and high-angular-resolution observations, we are able to resolve the morphology of the B field in the plane of sky and detect a great turn of 90 degree in the B field direction: Over the northern part of the clump, where a velocity gradient is evident, the B field is largely aligned with the long axis of the clump, whereas in the southern part, where the velocity field appears relatively uniform, the B field is slightly pinched with its mean direction perpendicular to the clump elongation. We suggest that the clump forms as its parent cloud collapses more along the large scale B field. In this process, the northern part carries over most of the angular momentum, forming a fast rotating system, and pulls the B field into a toroidal configuration. In contrast, the southern part is not sig...

  11. Characterisation of the core poloidal flow at ASDEX upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Lebschy, Alexander [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Physik-Department E28, Technische Universitaet Muenchen, D-85748 Garching (Germany); McDermott, Rachael M.; Geiger, Benedikt; Cavedon, Marco; Dunne, Michael G.; Dux, Ralph; Fischer, Rainer; Kappatou, Athina; McCarthy, Patrick J.; Viezzer, Eleonora [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Collaboration: the ASDEX Upgrade Team

    2016-07-01

    Plasma rotation has a strong influence on the transport of heat, particles, and momentum in fusion plasmas via a variety of mechanisms, for example, by the stabilization of modes and the suppression of plasma turbulence. In tokamaks, the toroidal rotation (u{sub tor}) is essentially a free parameter that is usually dominated by the external momentum input from neutral beams used to heat the plasma. The poloidal rotation (u{sub pol}), on the other hand, is strongly damped and is predicted to remain at Neoclassical (NC) levels of a few km/s. Measuring the inboard-outboard asymmetry of u{sub tor} with charge exchange recombination spectroscopy enables an indirect measurement of u{sub pol} and, hence, the measurement of the complete plasma flow on a flux surface. In order to characterise the nature of u{sub pol} at ASDEX Upgrade a poloidal rotation database has been built that contains a large variation in the parameters that, according to NC theory, drive u{sub pol}; namely, the main ion temperature and density gradients and collisionality. Initial results from this database and a detailed comparison of u{sub pol} to NC theory in interesting plasma scenarios, are presented in this poster.

  12. 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.

  13. Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium

    CERN Document Server

    Willensdorfer, M; Strumberger, E; Suttrop, W; Vanovac, B; Brida, D; Cavedon, M; Classen, I; Dunne, M; Fietz, S; Fischer, R; Kirk, A; Laggner, F M; Liu, Y Q; Odstrcil, T; Ryan, D A; Viezzer, E; Zohm, H; Luhmann, I C

    2016-01-01

    The plasma response from an external n = 2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To interpret ECE and ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport has been combined with ray tracing. The measured data is compared to synthetic ECE data generated from a 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC. The measured amplitudes of the helical displacement in the midplane are in reasonable agreement with the one from the synthetic VMEC diagnostics. Both exceed the vacuum field calculations and indicate the presence of an amplified kink response at the edge. Although the calculated magnetic structure of this edge kink peaks at poloidal mode numbers larger than the resonant components |m| > |nq|, the displacement measured by ECE-I is almost resonant |m| ~ |nq|. This is expected from ideal MHD in the proximity of rational surfaces. VMEC and MARS-...

  14. Nonlinear magnetic reconnection in low collisionality plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Ottaviani, M. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Porcelli, F. [Politecnico di Torino, Turin (Italy)

    1994-07-01

    The magnetic reconnection in collisionless regimes, where electron inertia is responsible for the decoupling of the plasma motion from that of the field lines, is discussed. Since the linear theory of m=1 modes breaks down for very small magnetic island widths, a non linear analysis is called for. Thus, the behaviour of a collisionless, 2-D fluid slab model in the limit {rho}/d -> 0, is analyzed. The main result is that, when the island size is larger than the linear layer but smaller than the equilibrium scale length, the reconnection rate exhibits a quasi-explosive time behaviour, during which a current density sub-layer narrower than the skin depth is formed. It is believed that the inclusion of the electron initial term in Ohm`s law opens the possibility to understand the rapidity of relaxation process observed in low collisionality plasmas. 7 refs., 6 figs.

  15. Molecular dynamics simulations of magnetized dusty plasmas

    Science.gov (United States)

    Piel, Alexander; Reichstein, Torben; Wilms, Jochen

    2012-10-01

    The combination of the electric field that confines a dust cloud with a static magnetic field generally leads to a rotation of the dust cloud. In weak magnetic fields, the Hall component of the ion flow exerts a drag force that sets the dust in rotation. We have performed detailed molecular-dynamics simulations of the dynamics of torus-shaped dust clouds in anodic plasmas. The stationary flow [1] is characterized by a shell structure in the laminar dust flow and by the spontaneous formation of a shear-flow around a stationary vortex. Here we present new results on dynamic phenomena, among them fluctuations due to a Kelvin-Helmholtz instability in the shear-flow. The simulations are compared with experimental results. [4pt] [1] T. Reichstein, A. Piel, Phys. Plasmas 18, 083705 (2011)

  16. Magnetic equilibria for X-Diverted plasmas

    Science.gov (United States)

    Pekker, M.; Valanju, P.; Kotschenreuther, M.; Wiley, J.; Mahajan, S.

    2006-10-01

    The X-divertor has been proposed to solve heat exhaust problems for reactors beyond ITER. By generating an extra X-point downstream from the main X-point, the X-divertor greatly expands magnetic flux at the divertor plates. As a result, the heat is distributed over a larger area and the line length is greatly increased. We have developed coil sets for X-diverted magnetic equilibria for many devices (NSTX, PEGASUS, EAST, HL-2A, CREST, and a CTF). These demonstrate that the XD configuration can be created for highly shaped plasmas using moderate coil currents. For reactors, all coils can be placed behind 1 m of shielding. We have also shown that XD configurations are robust to modest plasma perturbations and VDEs; this is in contrast to the sensitivity of highly tilted divertor plates.

  17. Plasma Processes : Sheath and plasma parameters in a magnetized plasma system

    Indian Academy of Sciences (India)

    Bornali Singha; A Sharma; J Chutia

    2000-11-01

    The variation of electron temperature and plasma density in a magnetized 2 plasma is studied experimentally in presence of a grid placed at the middle of the system. Plasma leaks through the negatively biased grid from the source region into the diffused region. It is observed that the electron temperature increases with the magnetic field in the diffused region whereas it decreases in the source region of the system for a constant grid biasing voltage. Also, investigation is done to see the change of electron temperature with grid biasing voltage for a constant magnetic field. This is accompanied by the study of the variation of sheath structure across the grid for different magnetic field and grid biasing voltage as well. It reveals that with increasing magnetic field and negative grid biasing voltage, the sheath thickness expands.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, Seiya, E-mail: n-seiya@kobe-kosen.ac.jp [Kobe City College of Technology, Kobe, Hyogo 651-2194 (Japan)

    2014-12-15

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

  19. Comparison of edge turbulence imaging at two different poloidal locations in the scrape-off layer of Alcator C-Mod

    Energy Technology Data Exchange (ETDEWEB)

    Zweben, S. J.; Davis, W. M.; Diallo, A.; Ellis, R. A.; Stotler, D. P. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States); Terry, J. L.; Golfinopoulos, T.; Hughes, J. W.; LaBombard, B.; Landreman, M. [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Agostini, M. [Consorzio RFX, Associazione Euratom-ENEA sulla fusione, C.so Stati Uniti 4, I-3512 Padova (Italy); Grulke, O. [Max Planck Institute for Plasma Physics, EURATOM Association, D-17491 Greifswald (Germany); Myra, J. R. [Lodestar Research Corporation, 2400 Central Ave., Boulder, Colorado 80301 (United States); Pace, D. C. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)

    2013-07-15

    This paper describes 2D imaging measurements of plasma turbulence made in the scrape-off layer of the Alcator C-Mod tokamak simultaneously at two different poloidal locations, one near the outer midplane and the other near the divertor X-point region. These images were made with radial and poloidal resolution using two gas puff imaging diagnostics not directly connected along a B field line. The turbulence correlation structure has a significantly different tilt angle with respect to the local flux surfaces for the midplane and X-regions, and a slightly different ellipticity and size. The time-averaged turbulence velocities can be different in the midplane and X-regions, even within the same flux surface in the same shot. The structures are partially consistent with a magnetic flux tube mapping model, and the velocities are compared with various models for turbulence flow.

  20. Generalized Langmuir Waves in Magnetized Kinetic Plasmas

    Science.gov (United States)

    Willes, A. J.; Cairns, Iver H.

    2000-01-01

    The properties of unmagnetized Langmuir waves and cold plasma magnetoionic waves (x, o, z and whistler) are well known. However, the connections between these modes in a magnetized kinetic plasma have not been explored in detail. Here, wave properties are investigated by numerically solving the dispersion equation derived from the Vlasov equations both with and without a beam instability present. For omega(sub p)>Omega(sub e), it is shown that the generalized Langmuir mode at oblique propagation angles has magnetic z-mode characteristics at low wave numbers and thermal Langmuir mode characteristics at high wave numbers. For omega(sub p)Langmuir mode instead connects to the whistler mode at low wave numbers. The transition from the Langmuir/z mode to the Langmuir/whistler mode near omega(sub p) = Omega(sub e) is rapid. In addition, the effects on wave dispersion and polarization after adding a beam are investigated. Applications of this theory to magnetized Langmuir waves in Earth's foreshock and the solar wind, to waves observed near the plasma frequency in the auroral regions, and to solar type III bursts are discussed.

  1. Plasma Braking Due to External Magnetic Perturbations

    Science.gov (United States)

    Frassinetti, L.; Olofsson, Kejo; Brunsell, P. R.; Khan, M. W. M.; Drake, J. R.

    2010-11-01

    The RFP EXTRAP T2R is equipped with a comprehensive active feedback system (128 active saddle coils in the full-coverage array) and active control of both resonant and non-resonant MHD modes has been demonstrated. The feedback algorithms, based on modern control methodology such as reference mode tracking (both amplitude and phase), are a useful tool to improve the ``state of the art'' of the MHD mode control. But this tool can be used also to improve the understanding and the characterization of other phenomena such as the ELM mitigation with a resonant magnetic perturbation or the plasma viscosity. The present work studies plasma and mode braking due to static RMPs. Results show that a static RMP produces a global braking of the flow profile. The study of the effect of RMPs characterized by different helicities will also give information on the plasma viscosity profile. Experimental results are finally compared to theoretical models.

  2. Plasma opening switch with extrinsic magnetic field

    CERN Document Server

    Dolgachev, G; Maslennikov, D

    2001-01-01

    Summary form only given, as follows. We have demonstrated in series of experiments that plasma opening switch (POS) switching voltage (UPOS) is defined by energy density (w) deposited in the POS plasma. If we then consider a plasma erosion mainly responsible for the effect of POS switching (the erosion effect could be described by Hall or Child-Langmuir models) the energy density (w) could be measured as a function of a system "macro-parameter" such as the initial charging voltage of the capacity storage system (the Marx pulsed voltage generator) UMarx. The POS voltage in this case could be given by UPOS"aw=aUMarx4/7, where a is a constant. This report demonstrates that for the high-impedance POS which has limited charge density transferred through the POS plasma a"2.5 (MV3/7) with no external magnetic field applied. The use of the extrinsic magnetic field allows to increase a up to 3.6 (MV3/7) and to achieve higher voltages at the opening phase - UPOS=3.6UMarx4/7. To verify this approach set of experimental ...

  3. Proton acceleration from magnetized overdense plasmas

    Science.gov (United States)

    Kuri, Deep Kumar; Das, Nilakshi; Patel, Kartik

    2017-01-01

    Proton acceleration by an ultraintense short pulse circularly polarized laser from an overdense three dimensional (3D) particle-in-cell (PIC) 3D-PIC simulations. The axial magnetic field modifies the dielectric constant of the plasma, which causes a difference in the behaviour of ponderomotive force in case of left and right circularly polarized laser pulse. When the laser is right circularly polarized, the ponderomotive force gets enhanced due to cyclotron effects generating high energetic electrons, which, on reaching the target rear side accelerates the protons via target normal sheath acceleration process. On the other hand, in case of left circular polarization, the effects get reversed causing a suppression of the ponderomotive force at a short distance and lead towards a rise in the radiation pressure, which results in the effective formation of laser piston. Thus, the axial magnetic field enhances the effect of radiation pressure in case of left circularly polarized laser resulting in the generation of high energetic protons at the target front side. The transverse motion of protons get reduced as they gyrate around the axial magnetic field which increases the beam collimation to some extent. The optimum thickness of the overdense plasma target is found to be increased in the presence of an axial magnetic field.

  4. Kinetic intermittency in magnetized plasma turbulence

    CERN Document Server

    Teaca, Bogdan; Told, Daniel; Jenko, Frank

    2016-01-01

    We employ magnetized plasma turbulence, described by a gyrokinetic formalism in an interval ranging from the end of the fluid scales to the electron gyroradius, to introduce the first study of kinetic intermittency, in which nonlinear structures formed directly in the distribution functions are analyzed by accounting for velocity space correlations generated by linear (Landau resonance) and nonlinear phase mixing. Electron structures are found to be strongly intermittent and dominated by linear phase mixing, while nonlinear phase mixing dominates the weakly intermittent ions. This is the first time spatial intermittency and linear phase mixing are shown to be self-consistently linked for the electrons and, as the magnetic field follows the intermittency of the electrons at small scales, explain why magnetic islands are places dominated by Landau damping in steady state turbulence.

  5. Solar Flare Magnetic Fields and Plasmas

    CERN Document Server

    Fisher, George

    2012-01-01

    This volume is devoted to the dynamics and diagnostics of solar magnetic fields and plasmas in the Sun’s atmosphere. Five broad areas of current research in Solar Physics are presented: (1) New techniques for incorporating radiation transfer effects into three-dimensional magnetohydrodynamic models of the solar interior and atmosphere, (2) The connection between observed radiation processes occurring during flares and the underlying flare energy release and transport mechanisms, (3) The global balance of forces and momenta that occur during flares, (4) The data-analysis and theoretical tools needed to understand and assimilate vector magnetogram observations and (5) Connecting flare and CME phenomena to the topological properties of the magnetic field in the Solar Atmosphere. The role of the Sun’s magnetic field is a major emphasis of this book, which was inspired by a workshop honoring Richard C. (Dick) Canfield.  Dick has been making profound contributions to these areas of research over a long and pro...

  6. Magnetic Field Analysis of Plasma Guide in Galathea Trimyx

    Directory of Open Access Journals (Sweden)

    Jin Xianji

    2016-01-01

    Full Text Available You Galathea Trimyx is a kind of small size, multipole magnetic confinement devices in controlled thermonuclear fusion. Plasma guide is one of important part in Galathea Trimyx which is responsible for transporting fast and slow plasma bunches ejected from plasma gun. The distribution and uniformity of magnetic field in completed plasma guide is analyzed in detail, including in x -axis direction and in z-axis direction. On the basis, the motion of plasma in the guide is discussed.

  7. Experimental studies of high-confinement mode plasma response to non-axisymmetric magnetic perturbations in ASDEX Upgrade

    Science.gov (United States)

    Suttrop, W.; Kirk, A.; Nazikian, R.; Leuthold, N.; Strumberger, E.; Willensdorfer, M.; Cavedon, M.; Dunne, M.; Fischer, R.; Fietz, S.; Fuchs, J. C.; Liu, Y. Q.; McDermott, R. M.; Orain, F.; Ryan, D. A.; Viezzer, E.; The ASDEX Upgrade Team; The DIII-D Team; The Eurofusion MST1 Team

    2017-01-01

    The interaction of externally applied small non-axisymmetric magnetic perturbations (MP) with tokamak high-confinement mode (H-mode) plasmas is reviewed and illustrated by recent experiments in ASDEX Upgrade. The plasma response to the vacuum MP field is amplified by stable ideal kink modes with low toroidal mode number n driven by the H-mode edge pressure gradient (and associated bootstrap current) which is experimentally evidenced by an observable shift of the poloidal mode number m away from field alignment (m  =  qn, with q being the safety factor) at the response maximum. A torque scan experiment demonstrates the importance of the perpendicular electron flow for shielding of the resonant magnetic perturbation, as expected from a two-fluid MHD picture. Two significant effects of MP occur in H-mode plasmas at low pedestal collisionality, ν \\text{ped}\\ast≤slant 0.4 : (a) a reduction of the global plasma density by up to 61 % and (b) a reduction of the energy loss associated with edge localised modes (ELMs) by a factor of up to 9. A comprehensive database of ELM mitigation pulses at low {ν\\ast} in ASDEX Upgrade shows that the degree of ELM mitigation correlates with the reduction of pedestal pressure which in turn is limited and defined by the onset of ELMs, i. e. a modification of the ELM stability limit by the magnetic perturbation.

  8. Expansion of a plasma cloud in a uniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Gorbachev, L.P.

    1984-10-01

    The last stage of the expansion of a plasma in vacuum in the presence of a uniform magnetic field is investigated. The velocity of plasma expansion and the electrical conductivity of the plasma are such that the Reynolds number is considered to be small; under these conditions the induced magnetic field is neglected. By assuming that the density of the plasma and its electrical conductivity are functions of time alone, the expansion velocity of the plasma, the shape of the boundary, and the magnetic moment of the plasma cloud are determined from equations of magnetogasdynamics. 8 references.

  9. Magnetic turbulence in the plasma sheet

    CERN Document Server

    Vörös, Z; Nakamura, R; Runov, A; Zhang, T L; Eichelberger, H U; Treumann, R A; Georgescu, E; Balogh, A; Klecker, B; R`eme, H

    2004-01-01

    Small-scale magnetic turbulence observed by the Cluster spacecraft in the plasma sheet is investigated by means of a wavelet estimator suitable for detecting distinct scaling characteristics even in noisy measurements. The spectral estimators used for this purpose are affected by a frequency dependent bias. The variances of the wavelet coefficients, however, match the power-law shaped spectra, which makes the wavelet estimator essentially unbiased. These scaling characteristics of the magnetic field data appear to be essentially non-steady and intermittent. The scaling properties of bursty bulk flow (BBF) and non-BBF associated magnetic fluctuations are analysed with the aim of understanding processes of energy transfer between scales. Small-scale ($\\sim 0.08-0.3$ s) magnetic fluctuations having the same scaling index $\\alpha \\sim 2.6$ as the large-scale ($\\sim 0.7-5$ s) magnetic fluctuations occur during BBF-associated periods. During non-BBF associated periods the energy transfer to small scales is absent, ...

  10. Design of a Compact Coaxial Magnetized Plasma Gun for Magnetic Bubble Expansion Experiments

    Science.gov (United States)

    2009-06-01

    COAXIAL MAGNETIZED PLASMA GUN FOR MAGNETIC BUBBLE EXPANSION EXPERIMENTS Y. Zhang1, A. G. Lynn1, S. C. Hsu2, M. Gilmore1, C... coaxial magnetized plasma gun and its associated hardware systems are discussed in detail. The plasma gun is used for experimental studies of...and coaxial plasma guns - which is the method employed in this work. The first coaxial plasma gun experiment was performed five decades ago by

  11. Transport barriers with and without shear flows in a magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Martinell, Julio J. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A. Postal 70-543, Mexico D.F. (Mexico)

    2014-01-14

    Different ways of producing a transport barrier in a toroidal magnetized plasma are discussed and the properties of the barriers are analyzed. The first mechanism is associated with the presence of a sheared plasma flow that is present in a limited region of the plasma, which creates a zonal flow. In contrast to the usual paradigm stating that the sheared flow reduces the turbulence correlation length and leads to suppression of the fluctuation driven transport in the region of highest shear, it is shown that from the perspective of chaotic transport of plasma particles in the fluctuation fields, the transport barrier is formed in the region of zero shear and it can be destroyed when the fluctuation level is high enough. It is also shown that finite gyroradius effects modify the dynamics and introduces new conditions for barrier formation. The second mechanism considers a method in which radio-frequency waves injected into the plasma can stabilize the drift waves and therefore the anomalous transport is reduced, creating a barrier. This process does not involve the presence of sheared flows and depends only on the effect of the RF wave field on the drift waves. The stabilizing effect in this case is due to the nonlinear ponderomotive force which acts in a way that offsets the pressure gradient destabilization. Finally, a mechanism based on the ponderomotive force of RF waves is described which produces poloidal plasma rotation around the resonant surface due to the asymmetry of induced transport; it creates a transport barrier by shear flow stabilization of turbulence.

  12. The Effect of Plasma Beta on High-n Ballooning Stability at Low Magnetic Shear

    CERN Document Server

    Connor, J W; Hastie, R J

    2016-01-01

    An explanation of the observed improvement in H-mode pedestal characteristics with increasing core plasma pressure or poloidal beta, as observed in MAST and JET, is sought in terms of the impact of the Shafranov shift, d', on ideal ballooning MHD stability.

  13. Investigating plasma motion of magnetic clouds at 1 AU through a velocity-modified cylindrical force-free flux rope model

    Science.gov (United States)

    Wang, Yuming; Zhou, Zhenjun; Shen, Chenglong; Liu, Rui; Wang, S.

    2015-03-01

    Magnetic clouds (MCs) are the interplanetary counterparts of coronal mass ejections (CMEs), and usually modeled by a flux rope. By assuming the quasi-steady evolution and self-similar expansion, we introduce three types of global motion into a cylindrical force-free flux rope model and developed a new velocity-modified model for MCs. The three types of the global motion are the linear propagating motion away from the Sun, the expanding, and the poloidal motion with respect to the axis of the MC. The model is applied to 72 MCs observed by Wind spacecraft to investigate the properties of the plasma motion of MCs. First, we find that some MCs had a significant propagation velocity perpendicular to the radial direction, suggesting the direct evidence of the CME's deflected propagation and/or rotation in interplanetary space. Second, we confirm the previous results that the expansion speed is correlated with the radial propagation speed and most MCs did not expand self-similarly at 1 AU. In our statistics, about 62%/17% of MCs underwent a underexpansion/overexpansion at 1 AU and the expansion rate is about 0.6 on average. Third, most interestingly, we find that a significant poloidal motion did exist in some MCs. Three speculations about the cause of the poloidal motion are therefore proposed. These findings advance our understanding of the MC's properties at 1 AU and the dynamic evolution of CMEs from the Sun to interplanetary space.

  14. Intense Magnetized Plasma-Wall Interaction

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Bruno S. [UNR; Fuelling, Stephan [UNR

    2013-11-30

    This research project studied wall-plasma interactions relevant to fusion science. Such interactions are a critical aspect of Magneto-Inertial Fusion (MIF) because flux compression by a pusher material, in particular the metal for the liner approach to MIF, involves strong eddy current heating on the surface of the pusher, and probably interactions and mixing of the pusher with the interior fuel during the time when fusion fuel is being burned. When the pusher material is a metal liner, high-energy-density conditions result in fascinating behavior. For example, "warm dense matter" is produced, for which material properties such as resistivity and opacity are not well known. In this project, the transformation into plasma of metal walls subjected to pulsed megagauss magnetic fields was studied with an experiment driven by the UNR 1 MA Zebra generator. The experiment was numerically simulated with using the MHRDR code. This simple, fundamental high-energy-density physics experiment, in a regime appropriate to MIF, has stimulated an important and fascinating comparison of numerical modeling codes and tables with experiment. In addition, we participated in developing the FRCHX experiment to compress a field-reversed-configuration (FRC) plasma with a liner, in collaboration with researchers from Air Force Research Laboratory and Los Alamos National Lab, and we helped develop diagnostics for the Plasma Liner Experiment (PLX) at LANL. Last, but not least, this project served to train students in high-energy-density physics.

  15. Magnetized laboratory plasma jets: Experiment and simulation

    Science.gov (United States)

    Schrafel, Peter; Bell, Kate; Greenly, John; Seyler, Charles; Kusse, Bruce

    2015-01-01

    Experiments involving radial foils on a 1 M A , 100 n s current driver can be used to study the ablation of thin foils and liners, produce extreme conditions relevant to laboratory astrophysics, and aid in computational code validation. This research focuses on the initial ablation phase of a 20 μ m Al foil (8111 alloy), in a radial configuration, driven by Cornell University's COBRA pulsed power generator. In these experiments ablated surface plasma (ASP) on the top side of the foil and a strongly collimated axial plasma jet are observed developing midway through the current rise. With experimental and computational results this work gives a detailed description of the role of the ASP in the formation of the plasma jet with and without an applied axial magnetic field. This ˜1 T field is applied by a Helmholtz-coil pair driven by a slow, 150 μ s current pulse and penetrates the load hardware before arrival of the COBRA pulse. Several effects of the applied magnetic field are observed: (1) without the field extreme-ultraviolet emission from the ASP shows considerable azimuthal asymmetry while with the field the ASP develops azimuthal motion that reduces this asymmetry, (2) this azimuthal motion slows the development of the jet when the field is applied, and (3) with the magnetic field the jet becomes less collimated and has a density minimum (hollowing) on the axis. PERSEUS, an XMHD code, has qualitatively and quantitatively reproduced all these experimental observations. The differences between this XMHD and an MHD code without a Hall current and inertial effects are discussed. In addition the PERSEUS results describe effects we were not able to resolve experimentally and suggest a line of future experiments with better diagnostics.

  16. Impact of toroidal and poloidal mode spectra on the control of non-axisymmetric fields in tokamaks

    Science.gov (United States)

    Lanctot, M. J.; Park, J.-K.; Piovesan, P.; Sun, Y.; Buttery, R. J.; Frassinetti, L.; Grierson, B. A.; Hanson, J. M.; Haskey, S. R.; In, Y.; Jeon, Y. M.; La Haye, R. J.; Logan, N. C.; Marrelli, L.; Orlov, D. M.; Paz-Soldan, C.; Wang, H. H.; Strait, E. J.

    2017-05-01

    In several tokamaks, non-axisymmetric magnetic field studies show that applied magnetic fields with a toroidal harmonic n = 2 can lead to disruptive n = 1 locked modes. In Ohmic plasmas, n = 2 magnetic reconnection thresholds in otherwise stable discharges are readily accessed at edge safety factors q ˜ 3, low density, and low rotation. Similar to previous studies with n = 1 fields, the thresholds are correlated with the "overlap" field computed with the IPEC code. The overlap field quantifies the plasma-mediated coupling of the external field to the resonant field. Remarkably, the "critical overlap fields" at which magnetic islands form are similar for applied n = 1 and 2 fields. The critical overlap field increases with plasma density and edge safety factor but is independent of the toroidal field. Poloidal harmonics m > nq dominate the drive for resonant fields while m 1 field control including the need for multiple rows of coils to control selected plasma parameters for specific functions (e.g., rotation control or ELM suppression).

  17. Comparison of Poloidal Velocity Meassurements to Neoclassical Theory on the National Spherical Torus Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Bell, R E; Kaye, S M; Kolesnikov, R A; LeBlance, B P; Rewolldt, G; Wang, W X

    2010-04-07

    Knowledge of poloidal velocity is necessary for the determination of the radial electric field, Er, which along with its gradient is linked to turbulence suppression and transport barrier formation. Recent measurements of poloidal flow on conventional tokamaks have been reported to be an order of magnitude larger than expected from neoclassical theory. In contrast, recent poloidal velocity measurements on the NSTX spherical torus [S. M. Kaye et al., Phys. Plasmas 8, 1977 (2001)] are near or below neoclassical estimates. A novel charge exchange recombination spectroscopy diagnostic is used, which features active and passive sets of up/down symmetric views to produce line-integrated poloidal velocity measurements that do not need atomic physics corrections. Local profiles are obtained with an inversion. Poloidal velocity measurements are compared with neoclassical values computed with the codes NCLASS [W. A. Houlberg et al., Phys. Plasmas 4, 3230 (1997)] and GTC-Neo [W. X. Wang, et al., Phys. Plasmas 13, 082501 (2006)], which has been updated to handle impurities. __________________________________________________

  18. Plasma response to m/n  =  3/1 resonant magnetic perturbation at J-TEXT Tokamak

    Science.gov (United States)

    Hu, Qiming; Li, Jianchao; Wang, Nengchao; Yu, Q.; Chen, Jie; Cheng, Zhifeng; Chen, Zhipeng; Ding, Yonghua; Jin, Hai; Li, Da; Li, Mao; Liu, Yang; Rao, Bo; Zhu, Lizhi; Zhuang, Ge; the J-TEXT Team

    2016-09-01

    The influence of resonant magnetic perturbations (RMPs) with a large m/n  =  3/1 component on electron density has been studied at J-TEXT tokamak by using externally applied static and rotating RMPs, where m and n are the poloidal and toroidal mode number, respectively. The detailed time evolution of electron density profile, measured by the polarimeter-interferometer, shows that the electron density n e first increases (decreases) inside (around/outside) of the 3/1 rational surface (RS), and it is increased globally later together with enhanced edge recycling. Associated with field penetration, the toroidal rotation around the 3/1 RS is accelerated in the co-I p direction and the poloidal rotation is changed from the electron to ion diamagnetic drift direction. Spontaneous unlocking-penetration circles occur after field penetration if the RMPs amplitude is not strong enough. For sufficiently strong RMPs, the 2/1 locked mode is also triggered due to mode coupling, and the global density is increased. The field penetration threshold is found to be linearly proportional to n eL (line-integrated density) at the 3/1 RS but to (n eL)0.73 for n e at the plasma core. In addition, for rotating RMPs with a large 3/1 component, field penetration causes a global increase in electron density.

  19. Equilibrium modeling of the TFCX poloidal field coil system

    Energy Technology Data Exchange (ETDEWEB)

    Strickler, D.J.; Miller, J.B.; Rothe, K.E.; Peng, Y.K.M.

    1984-04-01

    The Toroidal Fusion Core Experiment (TFCX) isproposed to be an ignition device with a low safety factor (q approx. = 2.0), rf or rf-assisted startup, long inductive burn pulse (approx. 300 s), and an elongated plasma cross section (kappa = 1.6) with moderate triangularity (delta = 0.3). System trade studies have been carried out to assist in choosing an appropriate candidate for TFCX conceptual design. This report describes an important element in these system studies - the magnetohydrodynamic (MHD) equilibrium modeling of the TFCX poloidal field (PF) coil system and its impact on the choice of machine size. Reference design points for the all-super-conducting toroidal field (TF) coil (TFCX-S) and hybrid (TFCX-H) options are presented that satisfy given PF system criteria, including volt-second requirements during burn, mechanical configuration constraints, maximum field constraints at the superconducting PF coils, and plasma shape parameters. Poloidal coil current waveforms for the TFCX-S and TFCX-H reference designs consistent with the equilibrium requirements of the plasma startup, heating, and burn phases of a typical discharge scenario are calculated. Finally, a possible option for quasi-steady-state operation is discussed.

  20. Penetration of conductive plasma flows across a magnetic field

    Science.gov (United States)

    Plechaty, Christopher Ryan

    2008-02-01

    Plasma interacts with magnetic fields in a variety of natural and laboratory settings. While a magnetic field "traps" isolated charged particles, plasma penetration across magnetic field is observed in many situations where a plasma-magnetic interface exists. For example, in the realm of pulsed power technology, this behavior is important for magnetically insulated transmission lines and for plasma opening switches. In the realm of astrophysics, the nature of the interaction between the solar wind plasma and the Earth's magnetic field affects the reliability of telecommunication devices and satellites. Experiments were performed at the Nevada Terawatt Facility to investigate how a conductive plasma penetrates an externally applied magnetic field. In experiment, a plasma flow was produced by laser ablation. This plasma was observed to penetrate an externally applied magnetic field produced by a 0.6 MA pulsed power generator. In experiment, the duration of the laser pulse was changed by three orders of magnitude, from ns (GW pulse power) to ps (TW) . This resulted in a significant variation of the plasma parameters, which in turn led to the actuation of different magnetic field penetration mechanisms.

  1. Convective radial energy flux due to resonant magnetic perturbations and magnetic curvature at the tokamak plasma edge

    CERN Document Server

    Marcus, F A; Fuhr, G; Monnier, A; Benkadda, S

    2014-01-01

    With the resonant magnetic perturbations (RMPs) consolidating as an important tool to control the transport barrier relaxation, the mechanism on how they work is still a subject to be clearly understood. In this work we investigate the equilibrium states in the presence of RMPs for a reduced MHD model using 3D electromagnetic fluid numerical code (EMEDGE3D) with a single harmonic RMP (single magnetic island chain) and multiple harmonics RMPs in cylindrical and toroidal geometry. Two different equilibrium states were found in the presence of the RMPs with different characteristics for each of the geometries used. For the cylindrical geometry in the presence of a single RMP, the equilibrium state is characterized by a strong convective radial thermal flux and the generation of a mean poloidal velocity shear. In contrast, for toroidal geometry the thermal flux is dominated by the magnetic flutter. For multiple RMPs, the high amplitude of the convective flux and poloidal rotation are basically the same in cylindr...

  2. Development of a magnetized coaxial plasma gun for compact toroid injection into the C-2 field-reversed configuration device.

    Science.gov (United States)

    Matsumoto, T; Sekiguchi, J; Asai, T; Gota, H; Garate, E; Allfrey, I; Valentine, T; Morehouse, M; Roche, T; Kinley, J; Aefsky, S; Cordero, M; Waggoner, W; Binderbauer, M; Tajima, T

    2016-05-01

    A compact toroid (CT) injector was developed for the C-2 device, primarily for refueling of field-reversed configurations. The CTs are formed by a magnetized coaxial plasma gun (MCPG), which consists of coaxial cylindrical electrodes and a bias coil for creating a magnetic field. First, a plasma ring is generated by a discharge between the electrodes and is accelerated by Lorenz self-force. Then, the plasma ring is captured by an interlinkage flux (poloidal flux). Finally, the fully formed CT is ejected from the MCPG. The MCPG described herein has two gas injection ports that are arranged tangentially on the outer electrode. A tungsten-coated inner electrode has a head which can be replaced with a longer one to extend the length of the acceleration region for the CT. The developed MCPG has achieved supersonic CT velocities of ∼100 km/s. Plasma parameters for electron density, electron temperature, and the number of particles are ∼5 × 10(21) m(-3), ∼40 eV, and 0.5-1.0 × 10(19), respectively.

  3. Magnetized plasma jets in experiment and simulation

    Science.gov (United States)

    Schrafel, Peter; Greenly, John; Gourdain, Pierre; Seyler, Charles; Blesener, Kate; Kusse, Bruce

    2013-10-01

    This research focuses on the initial ablation phase of a thing (20 micron) Al foil driven on the 1 MA-in-100 ns COBRA through a 5 mm diameter cathode in a radial configuration. In these experiments, ablated surface plasma (ASP) on the top of the foil and a strongly collimated axial plasma jet can be observed developing midway through current-rise. Our goal is to establish the relationship between the ASP and the jet. These jets are of interest for their potential relevance to astrophysical phenomena. An independently pulsed 200 μF capacitor bank with a Helmholtz coil pair allows for the imposition of a slow (150 μs) and strong (~1 T) axial magnetic field on the experiment. Application of this field eliminates significant azimuthal asymmetry in extreme ultraviolet emission of the ASP. This asymmetry is likely a current filamentation instability. Laser-backlit shadowgraphy and interferometry confirm that the jet-hollowing is correlated with the application of the axial magnetic field. Visible spectroscopic measurements show a doppler shift consistent with an azimuthal velocity in the ASP caused by the applied B-field. Computational simulations with the XMHD code PERSEUS qualitatively agree with the experimental results.

  4. Magnetic component of gluon plasma and its viscosity

    Energy Technology Data Exchange (ETDEWEB)

    Chernodub, M.N. [CNRS, Laboratoire de Mathematiques et Physique Theorique, Universite Francois-Rabelais Tours, Parc de Grandmont, 37200 Tours (France); Department of Physics and Astronomy, University of Gent, Krijgslaan 281, S9, B-9000 Gent (Belgium); Verschelde, H. [Department of Physics and Astronomy, University of Gent, Krijgslaan 281, S9, B-9000 Gent (Belgium); Zakharov, V.I. [ITEP, B. Cheremushkinskaya 25, Moscow, 117218 (Russian Federation); Max-Planck-Institut fuer Physik, Foehringer Ring 6, 80805 Munich (Germany)

    2010-10-15

    We discuss the role of the magnetic degrees of freedom of the gluon plasma in its viscosity. The main assumption is that motions of the magnetic component and of the rest of the plasma can be considered as independent. The magnetic component in the deconfined phase is described by a three-dimensional (Euclidean) field theory. The parameters of the theory can be estimated phenomenologically. It is not ruled out that the magnetic component is superfluid.

  5. Magnetic stochasticity in gyrokinetic simulations of plasma microturbulence

    Energy Technology Data Exchange (ETDEWEB)

    Nevins, W M; Wang, E; Candy, J

    2010-02-12

    Analysis of the magnetic field structure from electromagnetic simulations of tokamak ion temperature gradient turbulence demonstrates that the magnetic field can be stochastic even at very low plasma pressure. The degree of magnetic stochasticity is quantified by evaluating the magnetic diffusion coefficient. We find that the magnetic stochasticity fails to produce a dramatic increase in the electron heat conductivity because the magnetic diffusion coefficient remains small.

  6. Runaway electrons as a diagnostic of plasma internal magnetic fluctuations

    Institute of Scientific and Technical Information of China (English)

    Zheng Yong-Zhen; Ding Xuan-Tong; Li Wen-Zhong

    2006-01-01

    The transport of runaway electrons in a high-temperature plasma is relatively easy to measure in a steady state experiment and a perturbation experiment, which provides runaway electron diffusion coefficient Dr. This diffusion coefficient is determined by internal magnetic fluctuations, so it can be interpreted in terms of a magnetic fluctuation level. The internal magnetic fluctuation level (br/BT) is estimated to be about (2-4)×-4 in the HL-1M plasma. The results presented here demonstrate the effectiveness of using runaway electron transport techniques to determine internal magnetic fluctuations. A profile of magnetic fluctuation level in the HL-1M plasma can be estimated from Dr.

  7. Spatial control of processing plasmas in a multicusp plasma source equipped with a movable magnetic filter

    Energy Technology Data Exchange (ETDEWEB)

    Fukumasa, O.; Naitou, H.; Sakiyama, S. (Yamaguchi Univ., Yamaguchi (Japan))

    1991-12-20

    The plasma chemical vapor deposition (p-CVD) method has been used in the preparation of various sorts of thin films such as hydrogenated amorphous silicon films and hydrogenated amorphous carbon films, etc. and the application feasibility of a magnetically filtered multicusp plasma source has been studied. In this paper, it is confirmed that plasma parameters (H {sub 2} - ch {sub 4} or Ar-CH {sub 4} plasmas) are spatially well controlled by using both a movable magnetic filter and a plasma grid. Plasma parameters change sharply across the magnetic filter at any filter position and the whole plasma is divided clearly into the region of source plasma with high-energy electrons and the region of diffused plasma without high-energy electrons. Concerning the role of the magnetic filter which reflects preferentially high-energy electrons, a study is made through computer simulation. 7 refs., 9 figs.

  8. A web application for poloidal field analysis on HL-2M

    Energy Technology Data Exchange (ETDEWEB)

    Song, X.M., E-mail: songxm@swip.ac.cn; Pan, W.; Chen, L.Y.; Song, X.; Li, X.D.

    2014-05-15

    Highlights: • An original way to develop web application with a new framework (jQuery + PHP + Matlab) is introduced. • A convenient but powerful application for electromagnetic calculation is implemented. • The web application can run in any popular browser, on any hardware and in any operating system. • No any plugin is needed; no any maintenance is required. - Abstract: Recently, many web tools [1–3] in fusion society have been designed and demonstrated, which has been proved to be powerful and convenient to fusion researchers. Many physicists and engineers need a tool to compute the poloidal magnetic field for some purposes (for example, the calibration of magnetic probes for EFIT, the field null structure analysis for control, the design of some plasma diagnostic systems), so to develop a powerful and convenient web application for the calculation of magnetic field and magnetic flux produced by PF coils is very important. In this paper, a web application tool for poloidal field analysis on HL-2M with a totally original framework is presented. This web application is full of dynamic and interactive interface, and can run in any popular browser (IE, safari, firefox, opera), on any hardware (smart phone, PC, ipad, Mac) and operating system (ios, android, windows, linux, Mac OS). No any plugins is needed. The three layers (jQuery + PHP + Matlab) of this framework are introduced. The front top client layer is developed by jQuery code. The middle layer, which plays a role of a bridge to connect the server and client through socket communication, is developed by PHP code. The behind server layer is developed by Matlab, which compute the magnetic field or magnetic flux through a Special Function called Complete Elliptic Integral, and returns the results in the client favorite way, either by table or by JPG image. The field null structure and the vertical and radial field structure calculated by this tool are introduced with details. The idea to design a web

  9. Self-diffusion in a dense magnetized plasma

    NARCIS (Netherlands)

    Cohen, J.S.; Suttorp, L.G.

    1984-01-01

    Self-diffusion through dense classical one-component plasmas in a uniform magnetic field is studied by means of renormalized kinetic theory. Extensions of the Landau and the Rostoker equations to plasmas of high density are derived. The coefficient of self-diffusion along the magnetic field is evalu

  10. On the generation of magnetic field enhanced microwave plasma line

    Science.gov (United States)

    Chen, Longwei; Zhao, Ying; Wu, Kenan; Wang, Qi; Meng, Yuedong; Ren, Zhaoxing

    2016-12-01

    Microwave linear plasmas sustained by surface waves have attracted much attention due to the potential abilities to generate large-scale and uniform non-equilibrium plasmas. An external magnetic field was generally applied to enhance and stabilize plasma sources because the magnetic field decreased the electron losses on the wall. The effects of magnetic field on the generation and propagation mechanisms of the microwave plasma were tentatively investigated based on a 2-D numerical model combining a coupled system of Maxwell's equations and continuity equations. The mobility of electrons and effective electric conductivity of the plasma were considered as a full tensor in the presence of magnetic field. Numerical results indicate that both cases of magnetic field in the axial-direction and radial-direction benefit the generation of a high-density plasma; the former one allows the microwave to propagate longer in the axis direction compared to the latter one. The time-averaged power flow density and the amplitude of the electric field on the inner rod of coaxial waveguide attenuate with the propagation of the microwave for both cases of with and without external magnetic field. The attenuation becomes smaller in the presence of appropriately higher axial-direction magnetic field, which allows more microwave energies to transmit along the axial direction. Meanwhile, the anisotropic properties of the plasma, like electron mobility, in the presence of the magnetic field confine more charged particles in the direction of the magnetic field line.

  11. Observation of Vortex Patterns in a Magnetized Dusty Plasma System

    Institute of Scientific and Technical Information of China (English)

    HUANG Feng; YE Maofu; WANG Long; LIU Yanhong

    2007-01-01

    Vortex patterns of dust particles have been observed in a magnetized dusty plasma system. The formation mechanism of two-dimensional (2D) vortex patterns has been investigated by analysing the forces acting on dust particles and molecular dynamics (MD) simulations in a 2D confined magnetized dusty plasma. It has been found that with a weak confining electric field and a strong magnetic field, the particles' trajectories will form a vortex shape. The simulation results agree with our experimental observations. In our experiments, vortex patterns can be induced via circular rotation of particles by changing the rf (radio-frequency) power in a magnetized dusty plasma.

  12. Parametric instabilities in magnetized bi-ion and dusty plasmas

    Indian Academy of Sciences (India)

    N F Cramer; M P Hertzberg; S V Vladimirov

    2003-12-01

    The excitation of low frequency modes of oscillations in a magnetized bi-ion or dusty plasma with parametric pumping of the magnetic field is analysed. The equation of motion governing the perturbed plasma is derived and parametrically excited transverse modes propagating along the magnetic field are found. With multiple ion species or charged dust present, a number of different circularly polarized modes can be excited. The stability of these modes is investigated as a function of the plasma parameters. The modulational instabilities of large amplitude normal modes, modified by the extra ion species or dust and propagating along the magnetic field, are also investigated.

  13. Photonic Weyl degeneracies in magnetized plasma

    Science.gov (United States)

    Gao, Wenlong; Yang, Biao; Lawrence, Mark; Fang, Fengzhou; Béri, Benjamin; Zhang, Shuang

    2016-08-01

    Weyl particles are elusive relativistic fermionic particles with vanishing mass. While not having been found as an elementary particle, they are found to emerge in solid-state materials where three-dimensional bands develop a topologically protected point-like crossing, a so-called Weyl point. Photonic Weyl points have been recently realised in three-dimensional photonic crystals with complex structures. Here we report the presence of a novel type of plasmonic Weyl points in a naturally existing medium--magnetized plasma, in which Weyl points arise as crossings between purely longitudinal plasma modes and transverse helical propagating modes. These photonic Weyl points are right at the critical transition between a Weyl point with the traditional closed finite equifrequency surfaces and the newly proposed `type II' Weyl points with open equifrequency surfaces. Striking observable features of plasmon Weyl points include a half k-plane chirality manifested in electromagnetic reflection. Our study introduces Weyl physics into homogeneous photonic media, which could pave way for realizing new topological photonic devices.

  14. Propagation of ion beams through a tenuous magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Chrien, E.F.; Valeo, E.J.; Kulsrud, R.M.; Oberman, C.R.

    1985-10-01

    When an ion beam is propagated through a plasma, the question of charge neutralization is critical to its propagation. We consider such a problem where the plasma is magnetized with magnetic field perpendicular to the beam. The plasma-number density and beam-number density are assumed comparable. We reduce the problem to a two-dimensional model, which we solve. The solution suggests that it should be possible to attain charge neutralization if the beam density is properly varied along itself.

  15. Low-n shear Alfven spectra in axisymmetric toroidal plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, C.Z.; Chance, M.S.

    1985-11-01

    In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown both analytically and numerically that the toroidicity not only breaks up the shear Alfven continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfven eigenmodes with frequencies inside the continuum gaps. Potential applications of the low-n toroidicity-induced shear Alfven eigenmodes on plasma heating and instabilities are addressed. 17 refs., 4 figs.

  16. Theory of electromagnetic fluctuations for magnetized multi-species plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, Roberto E., E-mail: roberto.navarro@ug.uchile.cl; Muñoz, Víctor [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Araneda, Jaime [Departamento de Física, Universidad de Concepción, Concepción 4070386 (Chile); Moya, Pablo S. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, Maryland 20771 (United States); Department of Physics, Catholic University of America, Washington, D. C. 20064 (United States); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, Maryland 20771 (United States); Valdivia, Juan A. [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Centro de Estudios Interdisciplinarios Básicos y Aplicados en Complejidad, CEIBA complejidad, Bogotá (Colombia)

    2014-09-15

    Analysis of electromagnetic fluctuations in plasma provides relevant information about the plasma state and its macroscopic properties. In particular, the solar wind persistently sustains a small but detectable level of magnetic fluctuation power even near thermal equilibrium. These fluctuations may be related to spontaneous electromagnetic fluctuations arising from the discreteness of charged particles. Here, we derive general expressions for the plasma fluctuations in a multi-species plasma following arbitrary distribution functions. This formalism, which generalizes and includes previous works on the subject, is then applied to the generation of electromagnetic fluctuations propagating along a background magnetic field in a plasma of two proton populations described by drifting bi-Maxwellians.

  17. Development of New Sputter System by Magnetic Null Plasma

    OpenAIRE

    敦田, 悟; 楊, 鍾煥; 川尻, 晋平; 成, 烈[ブン; 本田, 親久; 大坪, 昌久

    2004-01-01

    Abstract ###A new type of plasma system based on the magnetic neutral loop discharge (NLD) concept ###has been developed for sputter application. This system is characterized by plasma production ###around the multi null magnetic field on the electrode surface, where a capacitive RF electric ###field is applied. From the experimental results and numerical analysis of electron behavior in ###this system, we found that electrons around the magnetic null region on the target surface ###moved in ...

  18. Model of the Dynamics of Plasma-Wave Channels in Magnetized Plasmas

    Science.gov (United States)

    Shirokov, E. A.; Chugunov, Yu. V.

    2016-06-01

    We analyze the dynamics of the plasma-wave channels excited in magnetized plasmas in the whistler frequency range. A linear theory of excitation of a plasma waveguide by an external source is developed using the quasistatic approximation. Self-consistent spatio-temporal distributions of the electric field of quasipotential waves and plasma density, which are solutions of the nonlinear nonstationary problem of the ionizing self-channeling of waves in plasmas are found on the basis of the linear theory.

  19. Impact of toroidal and poloidal mode spectra on the control of non-axisymmetric fields in tokamaks

    Science.gov (United States)

    Lanctot, Matthew J.

    2016-10-01

    In several tokamaks, non-axisymmetric magnetic field studies show applied n=2 fields can lead to disruptive n=1 locked modes, suggesting nonlinear mode coupling. A multimode plasma response to n=2 fields can be observed in H-mode plasmas, in contrast to the single-mode response found in Ohmic plasmas. These effects highlight a role for n >1 error field correction in disruption avoidance, and identify additional degrees of freedom for 3D field optimization at high plasma pressure. In COMPASS, EAST, and DIII-D Ohmic plasmas, n=2 magnetic reconnection thresholds in otherwise stable discharges are readily accessed at edge safety factors q 3 and low density. Similar to previous studies, the thresholds are correlated with the ``overlap'' field for the dominant linear ideal MHD plasma mode calculated with the IPEC code. The overlap field measures the plasma-mediated coupling of the external field to the resonant field. Remarkably, the critical overlap fields are similar for n=1 and 2 fields with m >nq fields dominating the drive for resonant fields. Complementary experiments in RFX-Mod show fields with m elicit transport responses with differing poloidal spectrum dependences, including a reduction in toroidal angular momentum that is not fully recoverable using fields that imperfectly match the applied field. These results have motivated an international effort to document n=2 error field thresholds in order to establish control requirements for ITER. This work highlights unique requirements for n >1 control, including the need for multiple rows of coils to control selected plasma parameters for specific functions (e.g., rotation control or ELM suppression). Optimal multi-harmonic (n=1 and n=2) error field control may be achieved using control algorithms that continuously respond to time-varying 3D field sources and plasma parameters. Supported by the US DOE under DE-FC02-04ER54698.

  20. Multi-Scale Investigation of Sheared Flows In Magnetized Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Edward, Jr., Thomas [Auburn Univ., Auburn, AL (United States)

    2014-09-19

    Flows parallel and perpendicular to magnetic fields in a plasma are important phenomena in many areas of plasma science research. The presence of these spatially inhomogeneous flows is often associated with the stability of the plasma. In fusion plasmas, these sheared flows can be stabilizing while in space plasmas, these sheared flows can be destabilizing. Because of this, there is broad interest in understanding the coupling between plasma stability and plasma flows. This research project has engaged in a study of the plasma response to spatially inhomogeneous plasma flows using three different experimental devices: the Auburn Linear Experiment for Instability Studies (ALEXIS) and the Compact Toroidal Hybrid (CTH) stellarator devices at Auburn University, and the Space Plasma Simulation Chamber (SPSC) at the Naval Research Laboratory. This work has shown that there is a commonality of the plasma response to sheared flows across a wide range of plasma parameters and magnetic field geometries. The goal of this multi-device, multi-scale project is to understand how sheared flows established by the same underlying physical mechanisms lead to different plasma responses in fusion, laboratory, and space plasmas.

  1. Electrostatic Modes of Dusty Plasmas in a Uniform Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    王晓钢; 王春华

    2002-01-01

    Electrostatic dusty plasma waves in a uniform magnetic field are studied. Unless the magnetic field is extremely strong, the dust particles can hardly be magnetized, while however,electrons and ions are easily done so. Electrostatic modes in such dusty plasmas can then be investigated by making use of the "moderately magnetized" assumption of magnetized electrons and ions, and unmagnetized dust particles. In a high frequency range, due to the existence of dust component, both frequencies of Langmuir waves (parallel to the magnetic field) and upper hybrid waves (perpendicular to the field)are reduced. In the frequency range of ion waves, besides the effect on dust-ion-acoustic waves propagating parallel to the magnetic field, the frequency of ion cyclotron waves perpendicular to the magnetic field is also enhanced. In a very low dust frequency range, we find an "ion-cyclotrondust-acoustic" mode propagating across the field line with a frequency even slower than dust acoustic waves.

  2. Electronegative Plasma Sheath Structure in a Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    ZOU Xiu; LIU Jin-Yuan; WANG Zheng-Xiong; GONG Ye; LIU Yue; WANG Xiao-Gang

    2004-01-01

    @@ The structure of an electronegative plasma sheath in an oblique magnetic field is investigated with a fluid model. We assume the system consists of hot electrons and negative ions as well as cold positive ions. Densities of particles and distributions of the spacious potential in various states of magnetic field are studied. The result shows that the existence of magnetic field and negative ions has great effects on the plasma sheath structures. In addition, the effects of negative ion density and temperature on the structure of the electronegative plasma sheath are discussed.

  3. Dynamos driven by poloidal flows in untwisted, curved and flat Riemannian diffusive flux tubes

    CERN Document Server

    de Andrade, L C Garcia

    2010-01-01

    Recently Vishik anti-fast dynamo theorem, has been tested against non-stretching flux tubes [Phys Plasmas 15 (2008)]. In this paper, another anti-dynamo theorem, called Cowling's theorem, which states that axisymmetric magnetic fields cannot support dynamo action, is carefully tested against thick tubular and curved Riemannian untwisted flows, as well as thin flux tubes in diffusive and diffusionless media. In the non-diffusive media the Cowling's theorem is not violated in thin Riemann-flat untwisted flux tubes, where the Frenet curvature is negative. Nevertheless the diffusion action in the thin flux tube leads to a a dynamo action driven by poloidal flows as shown by Love and Gubbins (Geophysical Res.) in the context of geodynamos. Actually it is shown that a slow dynamo action is obtained. In this case the Frenet and Riemann curvature still vanishes. In the case of magnetic filaments in diffusive media dynamo action is obtained when the Frenet scalar curvature is negative. Since the Riemann curvature tens...

  4. High Magnetic field generation for laser-plasma experiments

    Energy Technology Data Exchange (ETDEWEB)

    Pollock, B B; Froula, D H; Davis, P F; Ross, J S; Fulkerson, S; Bower, J; Satariano, J; Price, D; Glenzer, S H

    2006-05-01

    An electromagnetic solenoid was developed to study the effect of magnetic fields on electron thermal transport in laser plasmas. The solenoid, which is driven by a pulsed power system suppling 30 kJ, achieves magnetic fields of 13 T. The field strength was measured on the solenoid axis with a magnetic probe and optical Zeeman splitting. The measurements agree well with analytical estimates. A method for optimizing the solenoid design to achieve magnetic fields exceeding 20 T is presented.

  5. High-frequency electric field amplification in a magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Timofeev, Aleksandr V [Russian Research Centre ' Kurchatov Institute' , Moscow (Russian Federation)

    2006-11-30

    In the investigation of cyclotron ion heating in systems designed for plasma isotope separation, the high-frequency (HF) electric field amplification effect was found to occur in equilibrium plasma. In the present article this effect is treated as a result of the interaction of the plasma placed in a constant external magnetic field with the HF modes of the vacuum chamber. Consistent elaboration of this approach allowed obtaining a clear interpretation of the HF electric field amplification effect and constructing a simple model of HF field excitation in a plasma column embedded in the external magnetic field. (methodological notes)

  6. Magnetized Target Fusion Propulsion: Plasma Injectors for MTF Guns

    Science.gov (United States)

    Griffin, Steven T.

    2003-01-01

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

  7. Practicality of magnetic compression for plasma density control

    CERN Document Server

    Gueroult, Renaud

    2016-01-01

    Plasma densification through magnetic compression has been suggested for time-resolved control of the wave properties in plasma-based accelerators. Using particle in cell simulations with real mass ratio, the practicality of large magnetic compression on timescales shorter than the ion gyro-period is investigated. For compression times shorter than the transit time of a compressional Alfven wave across the plasma slab, results show the formation of two counter-propagating shock waves, leading to a highly non-uniform plasma density profile. Furthermore, the plasma slab displays large hydromagnetic like oscillations after the driving field has reached steady state. Peak compression is obtained when the two shocks collide in the mid-plane. At this instant, very large plasma heating is observed, and plasma $\\beta$ is estimated to be about $1$. Although these results point out a densification mechanism quite different and more complex than initially envisioned, these features could possibly be advantageous in part...

  8. Global low-frequency modes in weakly ionized magnetized plasmas: effects of equilibrium plasma rotation

    Energy Technology Data Exchange (ETDEWEB)

    Sosenko, P.; Pierre, Th. [Universite Marseille, Lab. PIIM - UMR6633 CNRS, Centre Saint Jerome, 13 - Marseille (France); Zagorodny, A. [Nancy-1 Univ. Henri Poincare, Lab. de Physique des Milieux Ionises (LPMIA, UPRES-A), Nancy 54 (France); International Centre of Physics, Kyiv (Ukraine)

    2004-07-01

    The linear and non-linear properties of global low-frequency oscillations in cylindrical weakly ionized magnetized plasmas are investigated analytically for the conditions of equilibrium plasma rotation. The theoretical results are compared with the experimental observations of rotating plasmas in laboratory devices, such as Mistral and Mirabelle in France, and KIWI in Germany. (authors)

  9. Numerical Investigation of Plasma Flows in Magnetic Nozzles

    Science.gov (United States)

    Sankaran, Kamesh; Polzin, Kurt A.

    2009-01-01

    Magnetic nozzles are used in many laboratory experiments in which plasma flows are to be confined, cooled, accelerated, or directed. At present, however, there is no generally accepted theoretical description that explains the phenomena of plasma expansion in and detachment from an externally-imposed magnetic field. The latter is an especially important problem in the field of plasma propulsion, where the ionized gas must detach from the applied, solenoidal magnetic field to realize thrust production. In this paper we simulate a plasma flowing in the presence of an applied magnetic field using a multidimensional numerical simulation tool that includes theoretical models of the various dispersive and dissipative processes present in the plasma. This is an extension of the simulation tool employed in previous work by Sankaran et al. The new tool employs the same formulation of the governing equation set, but retains the axial and radial components of magnetic field and the azimuthal component of velocity that were neglected. We aim to compare the computational results with the various proposed magnetic nozzle detachment theories to develop an understanding of the physical mechanisms that cause detachment. An applied magnetic field topology is obtained using a magnetostatic field solver, and this field is superimposed on the time-dependent magnetic field induced in the plasma to provide a self-consistent field description. The applied magnetic field and model geometry match those found in experiments by Kuriki and Okada. 4 A schematic showing the setup used in those experiments is shown. We model this geometry because there is a substantial amount of experimental data that can be compared to our computations, allowing for validation of the model. In addition, comparison of the simulation results with the experimentally obtained plasma parameters will provide insight into the mechanisms that lead to plasma detachment, revealing how they scale with different input

  10. Understanding of Edge Plasmas in Magnetic Fusion Energy Devices

    Energy Technology Data Exchange (ETDEWEB)

    Rognlien, T

    2004-11-01

    A limited overview is given of the theoretical understanding of edge plasmas in fusion devices. This plasma occupies the thin region between the hot core plasma and material walls in magnetically confinement configurations. The region is often formed by a change in magnetic topology from close magnetic field lines (i.e., the core region) and open field lines that contact material surfaces (i.e., the scrape-off layer [SOL]), with the most common example being magnetically diverted tokamaks. The physics of this region is determined by the interaction of plasma with neutral gas in the presence of plasma turbulence, with impurity radiation being an important component. Recent advances in modeling strong, intermittent micro-turbulent edge-plasma transport is given, and the closely coupled self-consistent evolution of the edge-plasma profiles in tokamaks. In addition, selected new results are given for the characterization of edge-plasmas behavior in the areas of edge-pedestal relaxation and SOL transport via Edge-Localize Modes (ELMs), impurity formation including dust, and magnetic field-line stochasticity in tokamaks.

  11. Pattern formation in a complex plasma in high magnetic fields.

    Science.gov (United States)

    Schwabe, M; Konopka, U; Bandyopadhyay, P; Morfill, G E

    2011-05-27

    Low-pressure room-temperature neon, argon, krypton, and air plasmas were studied in magnetic fields up to flux densities of 2.3 T. Filaments appeared parallel to the magnetic field lines, and patterns such as spirals and concentric circles formed in the perpendicular direction. We link these effects to the magnetization of the ions. We also used a layer of embedded microparticles as probes in the plasma. Their motion changed dramatically from a collective rotation of the whole ensemble in moderate magnetic fields to a rotation in several small vortices centered at the filaments. © 2011 American Physical Society

  12. Periodical Plasma Structures Controlled by Oblique Magnetic Field

    CERN Document Server

    Schweigert, Irina

    2016-01-01

    The propulsion type plasma in oblique external magnetic field is studied in 2D3V PIC MCC simulations. A periodical structure with maxima of electron and ion densities appears with an increase of an obliqueness of magnetic field. These ridges of electron and ion densities are aligned with the magnetic field vector and shifted relative each other. As a result the two-dimensional double-layers structure forms in cylindrical plasma chamber. The ion and electron currents on the side wall are essential modulated by the oblique magnetic field.

  13. An Improved Neoclassical Drift-Magnetohydrodynamical Fluid Model of Helical Magnetic Island Equilibria in Tokamak Plasmas

    CERN Document Server

    Fitzpatrick, Richard

    2015-01-01

    The effect of the perturbed ion polarization current on the stability of neoclassical tearing modes is calculated using an improved, neoclassical, four-field, drift-MHD model. The calculation involves the self-consistent determination of the pressure and scalar electric potential profiles in the vicinity of the associated magnetic island chain, which allows the chain's propagation velocity to be fixed. Two regimes are considered. First, a regime in which neoclassical ion poloidal flow damping is not strong enough to enhance the magnitude of the polarization current (relative to that found in slab geometry). Second, a regime in which neoclassical ion poloidal flow damping is strong enough to significantly enhance the magnitude of the polarization current. In both regimes, two types of solution are considered. First, a freely rotating solution (i.e., an island chain that is not interacting with a static, resonant, magnetic perturbation). Second, a locked solution (i.e., an island chain that has been brought to ...

  14. Electromagnetic modes in cold magnetized strongly coupled plasmas

    OpenAIRE

    Tkachenko, I. M.; Ortner, J.; Rylyuk, V. M.

    1999-01-01

    The spectrum of electromagnetic waves propagating in a strongly coupled magnetized fully ionized hydrogen plasma is found. The ion motion and damping being neglected, the influence of the Coulomb coupling on the electromagnetic spectrum is analyzed.

  15. Occurrence of Equatorial Plasma Bubbles during Intense Magnetic Storms

    Directory of Open Access Journals (Sweden)

    Chao-Song Huang

    2011-01-01

    Full Text Available An important issue in low-latitude ionospheric space weather is how magnetic storms affect the generation of equatorial plasma bubbles. In this study, we present the measurements of the ion density and velocity in the evening equatorial ionosphere by the Defense Meteorological Satellite Program (DMSP satellites during 22 intense magnetic storms. The DMSP measurements show that deep ion density depletions (plasma bubbles are generated after the interplanetary magnetic field (IMF turns southward. The time delay between the IMF southward turning and the first DMSP detection of plasma depletions decreases with the minimum value of the IMF Bz, the maximum value of the interplanetary electric field (IEF Ey, and the magnitude of the Dst index. The results of this study provide strong evidence that penetration electric field associated with southward IMF during the main phase of magnetic storms increases the generation of equatorial plasma bubbles in the evening sector.

  16. Characteristics of Dust Plasma Sheath in an Oblique Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    ZOU Xiu

    2006-01-01

    @@ The characteristics of dust plasma sheath in an oblique magnetic field are investigated with a fluid model. Hot electrons, cold ions, neutral particles, and dust grains are taken into account in this system.

  17. Advancements of microwave diagnostics in magnetically confined plasmas

    NARCIS (Netherlands)

    Mase, A.; Kogi, Y.; Ito, N.; Yokota, Y.; Akaki, K.; Kawahata, K.; Nagayama, Y.; Tokuzawa, T.; Yamaguchi, S.; Hojo, H.; Oyama, N.; N C Luhmann Jr.,; Park, H. K.; Donne, A. J. H.

    2009-01-01

    Microwave to millimeter-wave diagnostic techniques such as interferometry, reflectometry, scattering and radiometry have been powerful tools for diagnosing magnetically confined plasmas. Recent advances in electronic devices and components together with computer technology have enabled the developme

  18. A solvable blob-model for magnetized plasmas

    Science.gov (United States)

    Pécseli, H. L.; Sortland, D. S.; Garcia, O. E.

    2016-11-01

    A simple analytically solvable model for blobs in magnetized plasmas is proposed. The model gives results for a scaling of the blob velocity and acceleration with varying plasma parameters. Limiting cases are considered: one where the plasma motion is strictly perpendicular to an externally imposed toroidal magnetic field, and one where the electrons can move along magnetic field lines to compensate partly the collective electric fields. For these limiting cases, the model predicts scaling laws for the dependence of the blob velocities and accelerations with varying plasma density, temperature and magnetic field strength. Also the scaling with the dominant ion mass is derived. The analysis is completed by including the effects of collisions between ions and neutrals.

  19. Zero-frequency magnetic fluctuations in homogeneous cosmic plasma revisited

    CERN Document Server

    Caruso, Francisco

    2011-01-01

    Magnetic fluctuations in a non-magnetized gaseous plasma is revisited and calculated without approximations, based on the fluctuation-dissipation theorem. It is argued that the present results are qualitative and quantitative different form previous one based on the same theorem. In particular, it is shown that it is not correct that the spectral intensity does not vary sensitively with $k_{cut}$. Also the simultaneous dependence of this intensity on the plasma and on the collisional frequencies are discussed.

  20. Zero-frequency magnetic fluctuations in homogeneous cosmic plasma revisited

    OpenAIRE

    Caruso, Francisco; Oguri, Vitor

    2011-01-01

    Magnetic fluctuations in a non-magnetized gaseous plasma is revisited and calculated without approximations, based on the fluctuation-dissipation theorem. It is argued that the present results are qualitative and quantitative different form previous one based on the same theorem. In particular, it is shown that it is not correct that the spectral intensity does not vary sensitively with $k_{cut}$. Also the simultaneous dependence of this intensity on the plasma and on the collisional frequenc...

  1. On Galateas - magnetic traps with plasma-embedded conductors

    Energy Technology Data Exchange (ETDEWEB)

    Morozov, A I [Russian Research Centre ' Kurchatov Institute' , Moscow (Russian Federation); Savel' ev, V V [M.V. Keldysh Institute for Applied Mathematics, Russian Academy of Sciences, Moscow (Russian Federation)

    1998-11-30

    The introduction of plasma-embedded magnetically insulated current-carrying conductors into a plasma trap magnetic system radically increases the number of possible trap designs. The present review focuses on the studies of {beta} = 1 Galateas conducted in the 1990s. Both general and design-specific Galatea properties are discussed and for a number of specific schemes analytical and numerical calculations are performed. Experimental data on a number of electrical discharge Galateas are presented. (reviews of topical problems)

  2. Thermonuclear reactions with magnetical confined plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Pinkau, K.; Schumacher, U.

    1982-09-01

    As the result of intensive research activities in the plasma physics one can expect that in future an independent burning plasma can be produced. The focal point of fusion research then will crescent shift on the answer of the question whether the technological development the design of a commercial working energy systems allows. The authors report on thermonuclear devices, plasma confinement, plasma heating, thermonuclear reactions and safety.

  3. Theory of magnetic reconnection in solar and astrophysical plasmas.

    Science.gov (United States)

    Pontin, David I

    2012-07-13

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

  4. Magnetic Bubble Expansion Experimental Investigation Using a Compact Coaxial Magnetized Plasma Gun

    Science.gov (United States)

    Zhang, Yue; Lynn, Alan; Hsu, Scott; Li, Hui; Liu, Wei; Gilmore, Mark; Watts, Christopher

    2009-11-01

    The poster will first discuss the construction and improved design of a compact coaxial magnetized plasma gun. The plasma gun is used for experimental studies of magnetic bubble expansion into a lower pressure background plasma, which as a model for extragalactic radio lobes and solar coronal mass ejections. In this experiment, the plasma bubble's density, electron temperature, and propagation speed are measured by using a multiple-tipped langmuir probe. Also a three axis B-dot probe array is used to measure the magnetic field in three dimensions during the expansion process. In this poster experiment setup and data will be provided. Finally the comparison with the simulation result will be made.

  5. Numerical Investigation of Plasma Detachment in Magnetic Nozzle Experiments

    Science.gov (United States)

    Sankaran, Kamesh; Polzin, Kurt A.

    2008-01-01

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

  6. Plasma Diagnostic and Performance of a Permanent Magnet Hall Thruster

    CERN Document Server

    Ferreira, J L; Rego, I D S; Ferreira, I S; Ferreira, Jose Leonardo; Souza, Joao Henrique Campos De; Rego, Israel Da Silveira; Ferreira, Ivan Soares

    2004-01-01

    Electric propulsion is now a sucessfull method for primary propulsion of deep space long duration missions and for geosyncronous satellite attitude control. Closed Drift Plasma Thruster, so called Hall Thruster or SPT (stationary plasma thruster) were primarily conceived in USSR (the ancient Soviet Union) and now it is been developed by space agencies, space research institutes and industries in several countries such as France, USA, Israel, Russian Federation and Brazil. In this work, we show plasma characteristics and performance of a Hall Thruster designed with an innovative concept which uses an array of permanent magnets, instead of an eletromagnet, to produce a radial magnetic field inside its cylindrical plasma drift channel. Within this new concept, we expect to develop a Hall Thruster within power consuption that will scale up to small and medium size satellites. A plasma density and temperature space profiles inside and outside the thruster channel will be shown. Space plasma potential, ion temperat...

  7. Simulating Magnetized Laboratory Plasmas with Smoothed Particle Hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Jeffrey N. [Univ. of California, Davis, CA (United States)

    2009-01-01

    The creation of plasmas in the laboratory continues to generate excitement in the physics community. Despite the best efforts of the intrepid plasma diagnostics community, the dynamics of these plasmas remains a difficult challenge to both the theorist and the experimentalist. This dissertation describes the simulation of strongly magnetized laboratory plasmas with Smoothed Particle Hydrodynamics (SPH), a method born of astrophysics but gaining broad support in the engineering community. We describe the mathematical formulation that best characterizes a strongly magnetized plasma under our circumstances of interest, and we review the SPH method and its application to astrophysical plasmas based on research by Phillips [1], Buerve [2], and Price and Monaghan [3]. Some modifications and extensions to this method are necessary to simulate terrestrial plasmas, such as a treatment of magnetic diffusion based on work by Brookshaw [4] and by Atluri [5]; we describe these changes as we turn our attention toward laboratory experiments. Test problems that verify the method are provided throughout the discussion. Finally, we apply our method to the compression of a magnetized plasma performed by the Compact Toroid Injection eXperiment (CTIX) [6] and show that the experimental results support our computed predictions.

  8. Magnetic fluctuation behavior during the transition between quasi-single helicity and multi helicity states in the reversed-field pinch plasma

    Science.gov (United States)

    Yambe, Kiyoyuki; Sakakita, Hajime; Hirano, Yoichi; Koguchi, Haruhisa

    2016-11-01

    We measured the variation of magnetic and electrostatic fluctuations observed during the transition between the quasi-single helicity (QSH) and multi helicity (MH) states in the edge region of the Toroidal Pinch Experiment-Reversed eXperiment reversed-field pinch plasma [Yagi et al., Fusion Eng. Des. 45, 421 (1999)]. The high-frequency magnetic fluctuations largely decrease at the start of the QSH state. During the QSH state, the toroidal and radial magnetic fluctuations slightly increase again between 12 and 18 kHz but the decrease in the poloidal magnetic fluctuation is maintained. The confinement of fast electrons may be improved in the period of the QSH state although the radial magnetic fluctuation increases between 12 and 18 kHz. It is suggested that the improved confinement of fast electrons may be obtained by the decrease in the fast radial magnetic fluctuation having the frequency higher than 20 kHz in the period of the QSH state. Contrarily, the transition from QSH to MH states occurs with the increase in the slow toroidal magnetic fluctuation having the frequency lower than 10 kHz. The QSH state may bring a good confinement of fast electrons by the reduced high-frequency magnetic fluctuation compared with the MH state.

  9. The influence of finite Larmor radius effects on the radial interchange motions of plasma filaments

    DEFF Research Database (Denmark)

    Madsen, Jens; Garcia, Odd E.; Larsen, Jeppe Stærk

    2011-01-01

    The influence of finite Larmor radius (FLR) effects on the perpendicular convection of isolated particle density filaments driven by interchange motions in magnetized plasmas is investigated using a two-moment gyrofluid model. By means of numerical simulations on a two-dimensional, bi-periodic do......The influence of finite Larmor radius (FLR) effects on the perpendicular convection of isolated particle density filaments driven by interchange motions in magnetized plasmas is investigated using a two-moment gyrofluid model. By means of numerical simulations on a two-dimensional, bi....... Due to FLR effects, the poloidal up-down symmetry in the particle density field observed in the zero Larmor radius limit is broken. The symmetry breaking implies a poloidal motion of the blobs in the BrB direction. At later times, the direction of the poloidal motion is reversed when the blob...

  10. Ablation plasma transport using multicusp magnetic field for laser ion source

    Science.gov (United States)

    Takahashi, K.; Umezawa, M.; Uchino, T.; Ikegami, K.; Sasaki, T.; Kikuchi, T.; Harada, N.

    2016-05-01

    We propose a plasma guiding method using multicusp magnetic field to transport the ablation plasma keeping the density for developing laser ion sources. To investigate the effect of guiding using the magnetic field on the ablation plasma, we demonstrated the transport of the laser ablation plasma in the multicusp magnetic field. The magnetic field was formed with eight permanent magnets and arranged to limit the plasma expansion in the radial direction. We investigated the variation of the plasma ion current density and charge distribution during transport in the magnetic field. The results indicate that the plasma is confined in the radial direction during the transport in the multicusp magnetic field.

  11. Test data from the US-Demonstration Poloidal Coil experiment

    Energy Technology Data Exchange (ETDEWEB)

    Painter, T.A.; Steeves, M.M.; Takayasu, M.; Gung, C.; Hoenig, M.O. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Fusion Center; Tsuji, H.; Ando, T.; Hiyama, T.; Takahashi, Y.; Nishi, M.; Yoshida, K.; Okuno, K.; Nakajima, H.; Kato, T.; Sugimoto, M.; Isono, T.; Kawano, K.; Koizumi, N.; Osikiri, M.; Hanawa, H.; Ouchi, H.; Ono, M.; Ishida, H.; Hiue, H.; Yoshida, J.; Kamiyauchi, Y.; Ouchi, T.; Tajiri, F.; Kon, Y.; Shimizu, H.; Matsuzaki, Y.; Oomori, S.; Tani, T.; Oomori, K.; Terakado, T.; Yagyu, J.; Oomori, H. [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Superconducting Magnet Lab.

    1992-01-01

    The US Demonstration Poloidal Field Coil (US-DPC) experiment took place successfully at the Japan Atomic Energy Research Institute (JAERI) in late 1990. The 8 MJ niobium-tin coil was leak tight; it performed very well in DC tests; it performed well in AC tests, achieving approximately 70% of its design goal. An unexpected ramp-rate barrier at high currents was identified. The barrier could not be explored in the regime of higher fields and slower ramp rates due to limitations of the background-field coils. This document presents the results of the experiment with as little editing as possible. The coil, conductor, and operating conditions are given. The intent is to present data in a form that can be used by magnet analysts and designers.

  12. Strongly Driven Magnetic Reconnection in a Magnetized High-Energy-Density Plasma

    Science.gov (United States)

    Fiksel, G.; Barnak, D. H.; Chang, P.-Y.; Haberberger, D.; Hu, S. X.; Ivancic, S.; Nilson, P. M.; Fox, W.; Deng, W.; Bhattacharjee, A.; Germaschewski, K.

    2014-10-01

    Magnetic reconnection in a magnetized high-energy-density plasma is characterized by measuring the dynamics of the plasma density and magnetic field between two counter-propagating and colliding plasma flows. The density and magnetic field were profiled using the 4 ω angular filter refractometry and fast proton deflectometry diagnostics, respectively. The plasma flows are created by irradiating oppositely placed plastic targets with 1.8-kJ, 2-ns laser beams on the OMEGA EP Laser System. The two plumes are magnetized by an externally controlled magnetic field with an x-type null point geometry with B = 0 at the midplane and B = 8 T at the targets. The interaction region is pre-filled with a low-density background plasma. The counterflowing super-Alfvénic plasma plumes sweep up and compress the magnetic field and the background plasma into a pair of magnetized ribbons, which collide, stagnate, and reconnect at the midplane, allowing for the first detailed observation of a stretched current sheet in laser-driven reconnection experiments. The measurements are in good agreement with first-principles particle-in-cell simulations. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and NLUF Grant DE-SC0008655.

  13. Steady-State Plasmas in KT5D Magnetized Torus

    Institute of Scientific and Technical Information of China (English)

    ZHU Zhenhua; LIU Wandong; WAN Baonian; ZHAO Yanping; LI Jiangang; YAN Longwen; YANG Qingwei; DING Xuantong; XU Min; YU Yi; WANG Zhijiang; LU Ronghua; WEN Yizhi; YU Changxuan; MA Jinxiu; WAN Shude

    2007-01-01

    Steady-state plasma generated by electron cyclotron resonance (ECR) wave in the KT5D magnetized torus was studied using a fast high-resolution camera and Langmuir probes. It was found that both the discharge patterns taken by the camera and the plasma parameters measured by the probes were very sensitive to the working gas pressure and the magnetic configuration of the torus both without and with vertical fields. There existed fast vertical motion of the plasma. Tentative discussion is presented about the observed phenomena such as the bright resonance layer at a high gas pressure and the wave absorption mechanism at a low pressure. Further explanations should be found.

  14. Magnetic Field Dependence and Q of the Josephson Plasma Resonance

    DEFF Research Database (Denmark)

    Pedersen, Niels Falsig; Finnegan, T. F.; Langenberg, D. N.

    1972-01-01

    The results of an experimental study of the magnetic field dependence of the Josephson-plasma-resonance frequency and linewidth in Pb-Pb oxide-Pb tunnel junctions are reported. In the presence of an external magnetic field, the plasma mode is found to be sensitive to an antisymmetric component...... of supercurrent density which is not observed in conventional measurements of the field-dependent critical current. The frequency and field dependence of the plasma-resonance linewidth are interpreted as evidence that the previously unobserved quasiparticle-pair-interference tunnel current predicted by Josephson...

  15. Collective fluctuations in magnetized plasma: Transition probability approach

    Energy Technology Data Exchange (ETDEWEB)

    Sosenko, P.P. [International Centre of Physics and M.M.Boholiubov Inst. for Theoretical Physics, Kyiv (Ukraine)]|[Ecole Polytechnique, Palaiseau (France)]|[Univ. Henri Poincare, Vandoeuvre (France)

    1997-10-01

    Statistical plasma electrodynamics is elaborated with special emphasis on the transition probability approach and quasi-particles, and on modern applications to magnetized plasmas. Fluctuation spectra in the magnetized plasma are calculated in the range of low frequencies (with respect to the cyclotron one), and the conditions for the transition from incoherent to collective fluctuations are established. The role of finite-Larmor-radius effects and particle polarization drift in such a transition is explained. The ion collective features in fluctuation spectra are studied. 63 refs., 30 figs.

  16. Observations of Magnetic Reconnection and Plasma Dynamics in Mercury's Magnetosphere

    Science.gov (United States)

    DiBraccio, Gina A.

    Mercury's magnetosphere is formed as a result of the supersonic solar wind interacting with the planet's intrinsic magnetic field. The combination of the weak planetary dipole moment and intense solar wind forcing of the inner heliosphere creates a unique space environment, which can teach us about planetary magnetospheres. In this work, we analyze the first in situ orbital observations at Mercury, provided by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. Magnetic reconnection and the transport of plasma and magnetic flux are investigated using MESSENGER Magnetometer and Fast Imaging Plasma Spectrometer measurements. Here, we report our results on the effect of magnetic reconnection and plasma dynamics on Mercury's space environment: (1) Mercury's magnetosphere is driven by frequent, intense magnetic reconnection observed in the form of magnetic field components normal to the magnetopause, BN, and as helical bundles of flux, called magnetic flux ropes, in the cross-tail current sheet. The high reconnection rates are determined to be a direct consequence of the low plasma beta, the ratio of plasma to magnetic pressure, in the inner heliosphere. (2) As upstream solar wind conditions vary, we find that reconnection occurs at Mercury's magnetopause for all orientations of the interplanetary magnetic field, independent of shear angle. During the most extreme solar wind forcing events, the influence of induction fields generated within Mercury's highly conducting core are negated by erosion due to persistent magnetopause reconnection. (3) We present the first observations of Mercury's plasma mantle, which forms as a result of magnetopause reconnection and allows solar wind plasma to enter into the high-latitude magnetotail through the dayside cusps. The energy dispersion observed in the plasma mantle protons is used to infer the cross-magnetosphere electric field, providing a direct measurement of solar wind momentum

  17. Interstellar Turbulent Magnetic Field Generation by Plasma Instabilities

    CERN Document Server

    Tautz, R C

    2013-01-01

    The maximum magnetic field strength generated by Weibel-type plasma instabilities is estimated for typical conditions in the interstellar medium. The relevant kinetic dispersion relations are evaluated by conducting a parameter study both for Maxwellian and for suprathermal particle distributions showing that micro Gauss magnetic fields can be generated. It is shown that, depending on the streaming velocity and the plasma temperatures, either the longitudinal or a transverse instability will be dominant. In the presence of an ambient magnetic field, the filamentation instability is typically suppressed while the two-stream and the classic Weibel instability are retained.

  18. MHD Simulations of the Plasma Flow in the Magnetic Nozzle

    Science.gov (United States)

    Smith, T. E. R.; Keidar, M.; Sankaran, K.; olzin, K. A.

    2013-01-01

    The magnetohydrodynamic (MHD) flow of plasma through a magnetic nozzle is simulated by solving the governing equations for the plasma flow in the presence of an static magnetic field representing the applied nozzle. This work will numerically investigate the flow and behavior of the plasma as the inlet plasma conditions and magnetic nozzle field strength are varied. The MHD simulations are useful for addressing issues such as plasma detachment and to can be used to gain insight into the physical processes present in plasma flows found in thrusters that use magnetic nozzles. In the model, the MHD equations for a plasma, with separate temperatures calculated for the electrons and ions, are integrated over a finite cell volume with flux through each face computed for each of the conserved variables (mass, momentum, magnetic flux, energy) [1]. Stokes theorem is used to convert the area integrals over the faces of each cell into line integrals around the boundaries of each face. The state of the plasma is described using models of the ionization level, ratio of specific heats, thermal conductivity, and plasma resistivity. Anisotropies in current conduction due to Hall effect are included, and the system is closed using a real-gas equation of state to describe the relationship between the plasma density, temperature, and pressure.A separate magnetostatic solver is used to calculate the applied magnetic field, which is assumed constant for these calculations. The total magnetic field is obtained through superposition of the solution for the applied magnetic field and the self-consistently computed induced magnetic fields that arise as the flowing plasma reacts to the presence of the applied field. A solution for the applied magnetic field is represented in Fig. 1 (from Ref. [2]), exhibiting the classic converging-diverging field pattern. Previous research was able to demonstrate effects such as back-emf at a super-Alfvenic flow, which significantly alters the shape of the

  19. Implicit Methods for the Magnetohydrodynamic Description of Magnetically Confined Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Jardin, S C

    2010-09-28

    Implicit algorithms are essential for predicting the slow growth and saturation of global instabilities in today’s magnetically confined fusion plasma experiments. Present day algorithms for obtaining implicit solutions to the magnetohydrodynamic (MHD) equations for highly magnetized plasma have their roots in algorithms used in the 1960s and 1970s. However, today’s computers and modern linear and non-linear solver techniques make practical much more comprehensive implicit algorithms than were previously possible. Combining these advanced implicit algorithms with highly accurate spatial representations of the vector fields describing the plasma flow and magnetic fields and with improved methods of calculating anisotropic thermal conduction now makes possible simulations of fusion experiments using realistic values of plasma parameters and actual configuration geometry.

  20. Surface waves in the magnetized, collisional dusty plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, B. P. [Department of Physics, Astronomy and Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney NSW 2109 (Australia); Vladimirov, S. V. [School of Physics, The University of Sydney, Sydney NSW 2006 (Australia); Faculty of Engineering, Yokohama National University, Yokohama 240-8501 (Japan); Metamaterials Laboratory, National Research University of Information Technology, Mechanics, and Optics, St. Petersburg 199034 (Russian Federation); Ishihara, O. [Faculty of Engineering, Yokohama National University, Yokohama 240-8501 (Japan)

    2013-10-15

    The properties of the low frequency surface waves in inhomogeneous, magnetized collisional complex dusty plasma are investigated in this work. The inhomogeneity is modelled by the two distinct regions of the dusty medium with different dust densities. The external magnetic field is assumed to be oriented along the interface dividing the two medium. It is shown that the collisional momentum exchange that is responsible for the relative drift between the plasma particles affects the propagation of the surface waves in the complex plasma via the Hall drift of the magnetic fluctuations. The propagation properties of the sausage and kink waves depend not only on the grain charge and size distribution but also on the ambient plasma thermal conditions.

  1. Collimation of laser-produced plasmas using axial magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Amitava; Harilal, Sivanandan S.; Hassan, Syed M.; Endo, Akira; Mocek, Tomas; Hassanein, A.

    2015-06-01

    We investigated the expansion dynamics of laser-produced plasmas expanding into an axial magnetic field. Plasmas were generated by focusing 1.064 µm Nd:YAG laser pulses onto a planar tin target in vacuum and allowed to expand into a 0.5 T magnetic-filed where field lines were aligned along the plume expansion direction. Gated images employing intensified CCD showed focusing of the plasma plume, which were also compared with results obtained using particle-in-cell modelling methods. The estimated density and temperature of the plasma plumes employing emission spectroscopy revealed significant changes in the presence and absence of the 0.5T magnetic field. In the presence of the field, the electron temperature is increased with distance from the target, while the density showed opposite effects.

  2. GigaGauss magnetic fields in under-dense plasma

    CERN Document Server

    Lecz, Zsolt; Seryi, Andrei; Andreev, Alexander

    2016-01-01

    Magnetic fields have a crucial role in physics at all scales, from synchrotrons and laser-driven plasma accelerators to astrophysics and nanotechnology. Large field strengths, beside the guiding of relativistic particles along a shorter curvature, allows the investigation of material in extreme conditions existing only in exotic astro-objects like neutron stars or pulsars. Here we propose a method for generating magnetic field on the GigaGauss level in under-dense plasma using high intensity laser pulses with azimuthally non-uniform intensity distribution. The interaction is studied with the help of three-dimensional particle-in-cell plasma simulation code. Beside the standard wake-field and bubble generation, such laser beam induces the rotational motion of electrons at the edge of evacuated plasma region. The combined axial magnetic and electric fields form a compact source of both high frequency radiation, due to coherent synchrotron emission, and low emittance, high density relativistic electron bunches. ...

  3. Magnetic Piston Propagation in a 100-ns Plasma Opening Switch

    Science.gov (United States)

    Weingarten, A.; Grabowski, C.; Chakrabarti, N.; Maron, Y.; Fruchtman, A.

    1998-11-01

    The propagation of a magnetic piston through the plasma of a 90-ns, 170-kA POS is observed by studying the electron density, magnetic field, and ion velocity evolution. For the prefilled plasma n_e=(2.2± 0.5)× 10^14 cm-3, and T_e=5.5± 1 eV. The plasma composition is studied from absolute line intensities and collisional-radiative calculations. Most of the plasma ions are protons (90% near the cathode) with the rest being mainly CIV. The Hall-MHD conditions are not fulfilled for our experiment and ion motion is significant. The 3D-resolved ne evolution during the current pulse is studied from the line intensities of ions doped in the plasma using laser evaporation, and the magnetic field from Zeeman splitting. A diagonal magnetic piston propagates from the generator towards the load at about half the proton Alfven velocity. The protons are specularly reflected by the piston, while the heavy ions cross the potential hill in the piston, acquiring a lower velocity. The proton reflection causes an increase of ne ahead of the piston, followed by a sharp (10-20 ns) and substantial drop in ne (to 10-50% from the initial value). The magnetic field distribution studied using chordal observation, and theoretical analysis of ne and the magnetic field evolution are presented.

  4. Fluctuations in the relativistic plasma and primordial magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Lemoine, D. (Institut d' Astrophysique de Paris, CNRS, 98bis Bd Arago, F-75014 Paris (France) DAEC, Observatoire de Paris, Universite Paris VII, CNRS (UA173), F-92195 Meudon Cedex (France))

    1995-03-15

    The stochastic fluctuations of the electromagnetic field in a relativistic electron-positron plasma are studied. The correlation functions of the fluctuating four-current, electric and magnetic fields are computed to leading order using the Schwinger-Keldysh closed time path formulation of thermal field theory. As an application, we consider the scenario proposed by Tajima [ital et] [ital al]. for generating a primordial magnetic field from thermal fluctuations in the prerecombination plasma. We compute the level of magnetic fluctuations sustained by the pair plasma at or before the epoch of big bang nucleosynthesis and conclude that the early Universe was pervaded by a strong low-frequency, albeit small-scale, random magnetic field. The astrophysical implications are briefly discussed.

  5. Apparatus for magnetic and electrostatic confinement of plasma

    Energy Technology Data Exchange (ETDEWEB)

    Rostoker, Norman; Binderbauer, Michl

    2016-07-05

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

  6. Nonlinear magnetic field transport in opening switch plasmas

    Science.gov (United States)

    Mason, R. J.; Auer, P. L.; Sudan, R. N.; Oliver, B. V.; Seyler, C. E.; Greenly, J. B.

    1993-04-01

    The nonlinear transport of magnetic field in collisionless plasmas, as present in the plasma opening switch (POS), using the implicit multifluid simulation code anthem [J. Comput. Phys. 71, 429 (1987)] is studied. The focus is on early time behavior in the electron-magnetohydrodynamic (EMHD) limit, with the ions fixed, and the electrons streaming as a fluid under the influence of ve×B Hall forces. Through simulation, magnetic penetration and magnetic exclusion waves are characterized, due to the Hall effect in the presence of transverse density gradients, and the interaction of these Hall waves with nonlinear diffusive disturbances from electron velocity advection, (veṡ∇)ve, is studied. It is shown how these mechanisms give rise to the anode magnetic insulation layer, central diffusion, and cathode potential hill structures seen in earlier opening switch plasmas studies.

  7. Screened Coulomb potential in a flowing magnetized plasma

    CERN Document Server

    Joost, Jan-Philip; Kählert, Hanno; Arran, Christopher; Bonitz, Michael

    2014-01-01

    The electrostatic potential of a moving dust grain in a complex plasma with magnetized ions is computed using linear response theory, thereby extending our previous work for unmagnetized plasmas [P. Ludwig et al., New J. Phys. 14, 053016 (2012)]. In addition to the magnetic field, our approach accounts for a finite ion temperature as well as ion-neutral collisions. Our recently introduced code \\texttt{Kielstream} is used for an efficient calculation of the dust potential. Increasing the magnetization of the ions, we find that the shape of the potential crucially depends on the Mach number $M$. In the regime of subsonic ion flow ($M1$ the magnetic field effectively suppresses the plasma wakefield.

  8. Spatial mode structures of electrostatic drift waves in a collisional cylindrical helicon plasma

    DEFF Research Database (Denmark)

    Schröder, C.; Grulke, O.; Klinger, T.;

    2004-01-01

    In a cylindrical helicon plasma, mode structures of coherent drift waves are studied in the poloidal plane, the plane perpendicular to the ambient magnetic field. The mode structures rotate with a constant angular velocity in the direction of the electron diamagnetic drift and show significant...

  9. Passive Spectroscopic Diagnostics for Magnetically-confined Fusion Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Stratton, B. C.; Biter, M.; Hill, K. W.; Hillis, D. L.; Hogan, J. T.

    2007-07-18

    Spectroscopy of radiation emitted by impurities and hydrogen isotopes plays an important role in the study of magnetically-confined fusion plasmas, both in determining the effects of impurities on plasma behavior and in measurements of plasma parameters such as electron and ion temperatures and densities, particle transport, and particle influx rates. This paper reviews spectroscopic diagnostics of plasma radiation that are excited by collisional processes in the plasma, which are termed 'passive' spectroscopic diagnostics to distinguish them from 'active' spectroscopic diagnostics involving injected particle and laser beams. A brief overview of the ionization balance in hot plasmas and the relevant line and continuum radiation excitation mechanisms is given. Instrumentation in the soft X-ray, vacuum ultraviolet, ultraviolet, visible, and near-infrared regions of the spectrum is described and examples of measurements are given. Paths for further development of these measurements and issues for their implementation in a burning plasma environment are discussed.

  10. Two-dimensional simulations of nonlinear beam-plasma interaction in isotropic and magnetized plasmas

    CERN Document Server

    Timofeev, I V

    2012-01-01

    Nonlinear interaction of a low density electron beam with a uniform plasma is studied using two-dimensional particle-in-cell (PIC) simulations. We focus on formation of coherent phase space structures in the case, when a wide two-dimensional wave spectrum is driven unstable, and we also study how nonlinear evolution of these structures is affected by the external magnetic field. In the case of isotropic plasma, nonlinear buildup of filamentation modes due to the combined effects of two-stream and oblique instabilities is found to exist and growth mechanisms of secondary instabilities destroying the BGK--type nonlinear wave are identified. In the weak magnetic field, the energy of beam-excited plasma waves at the nonlinear stage of beam-plasma interaction goes predominantly to the short-wavelength upper-hybrid waves propagating parallel to the magnetic field, whereas in the strong magnetic field the spectral energy is transferred to the electrostatic whistlers with oblique propagation.

  11. Effect of solenoidal magnetic field on drifting laser plasma

    Science.gov (United States)

    Takahashi, Kazumasa; Okamura, Masahiro; Sekine, Megumi; Cushing, Eric; Jandovitz, Peter

    2013-04-01

    An ion source for accelerators requires to provide a stable waveform with a certain pulse length appropriate to the application. The pulse length of laser ion source is easy to control because it is expected to be proportional to plasma drifting distance. However, current density decay is proportional to the cube of the drifting distance, so large current loss will occur under unconfined drift. We investigated the stability and current decay of a Nd:YAG laser generated copper plasma confined by a solenoidal field using a Faraday cup to measure the current waveform. It was found that the plasma was unstable at certain magnetic field strengths, so a baffle was introduced to limit the plasma diameter at injection and improve the stability. Magnetic field, solenoid length, and plasma diameter were varied in order to find the conditions that minimize current decay and maximize stability.

  12. Magnetized strongly coupled plasmas and how to realize them in a dusty plasma setup

    CERN Document Server

    Bonitz, M; Ott, T; Löwen, H

    2013-01-01

    Strongly coupled plasmas in which the interaction energy exceeds the kinetic energy play an important role in many astrophysical and laboratory systems including compact stars, laser plasmas and dusty plasmas. They exhibit many unusual collective properties, such as liquid or crystalline behaviour, peculiar oscillation spectra and transport properties. Recently, strongly coupled plasmas were studied in the presence of a strong magnetic field by computer simulations, and strong modifications of their transport properties and oscillation spectra were observed. While strong magnetization is common in stellar systems it is practically impossible to achieve in complex plasmas due to the large mass of the dust particles. Here we discuss a recently demonstrated approach to achieve very strong "magnetization" by a rotation of the neutral gas, and we present new results for macroscopic two-dimensional systems.

  13. AE activity during transient beta drops in high poloidal beta discharges

    Science.gov (United States)

    Huang, J.; Gong, X. Z.; Ren, Q. L.; Ding, S. Y.; Qian, J. P.; Pan, C. K.; Li, G. Q.; Heidbrink, W. W.; Garofalo, A. M.; McClenaghan, J.

    2016-10-01

    Enhanced AE activity has been observed during transient beta drops in high poloidal beta DIII-D discharges with internal transport barriers (ITBs). These drops in beta are believed to be caused by n=1 external kink modes. In some discharges, beta recovers within 200 ms but, in others, beta stays suppressed. A typical discharge has βP 3, qmin 3, and q95 12. The drop in beta affects both fast ions and thermal particles, and a drop is also observed in the density and rotation. The enhanced AE activity follows the instability that causes the beta drop, is largest at the lowest beta, and subsides as beta recovers. MHD stability analysis is planned. A database study of the plasma conditions associated with the collapse will be also presented. Supported in part by the US Department of Energy under DE-FC02-04ER54698, DE-AC05-06OR23100, and by the National Natural Science Foundation of China 11575249, and the National Magnetic Confinement Fusion Program of China No. 2015GB110005.

  14. Plasma heating via adiabatic magnetic compression-expansion cycle

    Science.gov (United States)

    Avinash, K.; Sengupta, M.; Ganesh, R.

    2016-06-01

    Heating of collisionless plasmas in closed adiabatic magnetic cycle comprising of a quasi static compression followed by a non quasi static constrained expansion against a constant external pressure is proposed. Thermodynamic constraints are derived to show that the plasma always gains heat in cycles having at least one non quasi static process. The turbulent relaxation of the plasma to the equilibrium state at the end of the non quasi static expansion is discussed and verified via 1D Particle in Cell (PIC) simulations. Applications of this scheme to heating plasmas in open configurations (mirror machines) and closed configurations (tokamak, reverse field pinche) are discussed.

  15. Three-dimensional global fluid simulations of cylindrical magnetized plasmas

    DEFF Research Database (Denmark)

    Naulin, Volker; Windisch, T.; Grulke, O.

    2008-01-01

    . Thus, it is possible to assess the reproductive and predictive capabilities of plasma simulations in unprecedented detail. Here, three-dimensional global fluid simulations of a cylindrical magnetized plasma are presented. This plasma is characterized by the existence of spatially localized sources...... and sinks. The traditional scale separation paradigm is not applied in the simulation model to account for the important evolution of the background profiles due to the dynamics of turbulent fluctuations. Furthermore, the fluid modeling of sheath boundary conditions, which determine the plasma conditions...

  16. Ideal magnetohydrodynamic simulations of unmagnetized dense plasma jet injection into a hot strongly magnetized plasma

    CERN Document Server

    Liu, Wei

    2010-01-01

    We present results from three-dimensional ideal magnetohydrodynamic simulations of unmagnetized dense plasma jet injection into a hot strongly magnetized plasma, with the aim of providing insight into core fueling of a tokamak with parameters relevant for ITER (International Thermonuclear Experimental Reactor) and NSTX (National Spherical Torus Experiment). Unmagnetized jet injection is similar to compact toroid injection but with higher possible injection density and total mass, as well as a potentially smaller footprint for the injector hardware. Our simulation results show that the unmagnetized dense jet is quickly magnetized upon injection. The penetration depth of the jet into the tokamak plasma is mostly dependent on the jet's initial kinetic energy while the jet's magnetic field determines its interior evolution. A key requirement for spatially precise fueling is for the jet's slowing-down time to be less than the time for the perturbed tokamak magnetic flux to relax due to magnetic reconnection. Thus ...

  17. Magnetic reconnection in high-energy-density plasmas in the presence of an external magnetic field

    Science.gov (United States)

    Fox, W.; Bhattacharjee, A.; Fiksel, G.; Nilson, P.; Hu, S.; Chang, P.-Y.; Barnak, D.; Betti, R.

    2012-10-01

    Magnetic reconnection has recently been observed and studied in high-energy-density, laser-produced plasmas. These experiments are interesting both for obtaining fundamental data on reconnection, and may also be relevant for inertial fusion, as this magnetic reconnection geometry, with multiple, colliding, magnetized plasma bubbles, occurs naturally inside ICF hohlraums. We present initial results of experiments conducted on the OMEGA EP facility on magnetic reconnection between colliding, magnetized blowoff plasmas. While in previous experiments the magnetic fields were self-generated in the plasma by the Biermann battery effect, in these experiments the seed magnetic field is generated by pulsing current through a pair of external foils using the MIFEDS current generator (Magneto-Inertial Fusion Electrical Discharge System) developed at LLE. Time-resolved images of the magnetic fields and plasma dynamics are obtained from proton radiography and x-ray self-emission, respectively. We present initial results of the experiments, including comparison to ``null'' experiments with zero MIFEDS magnetic field, and associated modeling using the radiation-hydro code DRACO and the particle-in-cell code PSC.

  18. Relativistic Magnetic Reconnection in Pair Plasmas in Three Dimensions

    CERN Document Server

    Kagan, Daniel; Spitkovsky, Anatoly

    2012-01-01

    We investigate guide-field magnetic reconnection and particle acceleration in relativistic pair plasmas with three-dimensional particle-in-cell (PIC) simulations of a kinetic-scale current sheet in a periodic geometry at low magnetizations. The tearing instability is the dominant mode in the current sheet for all guide field strengths, while the linear kink mode is less important even without guide field. Oblique modes seem to be suppressed entirely. In its nonlinear evolution, the reconnection layer develops a network of interconnected and interacting magnetic flux ropes. As smaller flux ropes merge into larger ones, the reconnection layer evolves toward a three-dimensional, disordered state in which the resulting flux rope segments contain magnetic substructure on plasma skin depth scales. Embedded in the flux ropes, we detect spatially and temporally intermittent sites of dissipation reflected in peaks in the parallel electric field. Magnetic dissipation and particle acceleration persist until the end of t...

  19. Evaluation of magnetic field due to ferromagnetic vacuum vessel in Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Nakayama, Takeshi; Abe, Mitsushi; Tadokoro, Takahiro [Hitachi Ltd., Hitachi, Ibaraki (Japan). Power and Industrial Systems R and D Div.; Miura, Yukitoshi; Suzuki, Norio; Sato, Masayasu; Sengoku, Seio

    1998-03-01

    We evaluated magnetic fields due to the ferromagnetic vacuum vessel (FVV) in the Hitachi Tokamak HT-2 experimentally and computationally, the results were extrapolated to the JFT-2M and ITER. The maximum amount of local poloidal field on the magnetic axis induced by the FVV port was about 5 mT in the HT-2. This is the allowable amount of the field to discharge plasma in the HT-2. The proportion of external poloidal field shielded by FVV is in inverse proportion to external toroidal field. The stronger the field induced by FVV, the smaller the distance between plasma center and vacuum vessel wall. The delay time of poloidal field penetration due to the FVV is small, as long as the toroidal field is supplied. (author)

  20. Structure of magnetic fields in intracluster cavities

    CERN Document Server

    Gourgouliatos, Konstantinos Nektarios; Lyutikov, Maxim

    2010-01-01

    Observations of clusters of galaxies show ubiquitous presence of X-ray cavities, presumably blown by the AGN jets. We consider magnetic field structures of these cavities. Stability requires that they contain both toroidal and poloidal magnetic fields, while realistic configurations should have vanishing magnetic field on the boundary. For axisymmetric configurations embedded in unmagnetized plasma, the continuity of poloidal and toroidal magnetic field components on the surface of the bubble then requires solving the elliptical Grad-Shafranov equation with both Dirichlet and Neumann boundary conditions. This leads to a double eigenvalue problem, relating the pressure gradients and the toroidal magnetic field to the radius of the bubble. We have found fully analytical stable solutions. This result is confirmed by numerical simulation. We present synthetic X-ray images and synchrotron emission profiles and evaluate the rotation measure for radiation traversing the bubble.

  1. Effects of magnetic fields on the quark–gluon plasma

    Energy Technology Data Exchange (ETDEWEB)

    Bali, G.S. [Institute for Theoretical Physics, Universität Regensburg, D-93040 Regensburg (Germany); Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Bruckmann, F. [Institute for Theoretical Physics, Universität Regensburg, D-93040 Regensburg (Germany); Endrődi, G., E-mail: gergely.endrodi@physik.uni-r.de [Institute for Theoretical Physics, Universität Regensburg, D-93040 Regensburg (Germany); Fodor, Z. [Eötvös University, Theoretical Physics, Pázmány P. s 1/A, H-1117, Budapest (Hungary); Bergische Universität Wuppertal, Theoretical Physics, 42119 Wuppertal (Germany); Jülich Supercomputing Centre, Forschungszentrum Jülich, D-52425 Jülich (Germany); Katz, S.D. [Eötvös University, Theoretical Physics, Pázmány P. s 1/A, H-1117, Budapest (Hungary); MTA-ELTE Lendület Lattice Gauge Theory Research Group (Hungary); Schäfer, A. [Institute for Theoretical Physics, Universität Regensburg, D-93040 Regensburg (Germany)

    2014-11-15

    In this talk, the response of the thermal QCD medium to external (electro)magnetic fields is studied using continuum extrapolated lattice results at physical quark masses. The magnetic susceptibility of QCD is calculated, revealing a strong paramagnetic response at high temperatures. This paramagnetism is shown to result in an anisotropic squeezing of the quark–gluon plasma in non-central heavy-ion collisions, implying a sizeable contribution to the elliptic flow. Another aspect is the magnetic response of topologically non-trivial domains to the magnetic field. We quantify this effect on the lattice and compare the results to a simple model estimate.

  2. Plasma Instabilities and Magnetic Field Growth in Clusters of Galaxies

    Science.gov (United States)

    Schekochihin, A. A.; Cowley, S. C.; Kulsrud, R. M.; Hammett, G. W.; Sharma, P.

    2005-08-01

    We show that under very general conditions, cluster plasmas threaded by weak magnetic fields are subject to very fast growing plasma instabilities driven by the anisotropy of the plasma pressure (viscous stress) with respect to the local direction of the magnetic field. Such an anisotropy will naturally arise in any weakly magnetized plasma that has low collisionality and is subject to stirring. The magnetic field must be sufficiently weak for the instabilities to occur, viz., β>~Re1/2. The instabilities are captured by the extended MHD model with Braginskii viscosity. However, their growth rates are proportional to the wavenumber down to the ion gyroscale, so MHD equations with Braginskii viscosity are not well posed and a fully kinetic treatment is necessary. The instabilities can lead to magnetic fields in clusters being amplified from seed strength of ~10-18 G to dynamically important strengths of ~10 μG on cosmologically trivial timescales (~108 yr). The fields produced during the amplification stage are at scales much smaller than observed. Predicting the saturated field scale and structure will require a kinetic theory of magnetized cluster turbulence.

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

    Energy Technology Data Exchange (ETDEWEB)

    Lynn, Alan G., E-mail: lynn@ece.unm.edu; Gilmore, Mark [Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2014-11-15

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

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

    Science.gov (United States)

    Lynn, Alan G.; Gilmore, Mark

    2014-11-01

    Magnetized Liner Inertial Fusion (MagLIF) experiments, where a metal liner is imploded to compress a magnetized seed plasma may generate peak magnetic fields ˜104 T (100 Megagauss) over small volumes (˜10-10m3) at high plasma densities (˜1028m-3) on 100 ns time scales. Such conditions are extremely challenging to diagnose. We discuss the possibility of, and issues involved in, using polarimetry techniques at x-ray wavelengths to measure magnetic fields under these extreme conditions.

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

    Science.gov (United States)

    Lynn, Alan G; Gilmore, Mark

    2014-11-01

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

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

    Science.gov (United States)

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

    2014-10-01

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

  7. Magnetic Null Points in Kinetic Simulations of Space Plasmas

    Science.gov (United States)

    Olshevsky, Vyacheslav; Deca, Jan; Divin, Andrey; Peng, Ivy Bo; Markidis, Stefano; Innocenti, Maria Elena; Cazzola, Emanuele; Lapenta, Giovanni

    2016-03-01

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

  8. Laser propagation and soliton generation in strongly magnetized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Feng, W.; Li, J. Q.; Kishimoto, Y. [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

    2016-03-15

    The propagation characteristics of various laser modes with different polarization, as well as the soliton generation in strongly magnetized plasmas are studied numerically through one-dimensional (1D) particle-in-cell (PIC) simulations and analytically by solving the laser wave equation. PIC simulations show that the laser heating efficiency substantially depends on the magnetic field strength, the propagation modes of the laser pulse and their intensities. Generally, large amplitude laser can efficiently heat the plasma with strong magnetic field. Theoretical analyses on the linear propagation of the laser pulse in both under-dense and over-dense magnetized plasmas are well confirmed by the numerical observations. Most interestingly, it is found that a standing or moving soliton with frequency lower than the laser frequency is generated in certain magnetic field strength and laser intensity range, which can greatly enhance the laser heating efficiency. The range of magnetic field strength for the right-hand circularly polarized (RCP) soliton formation with high and low frequencies is identified by solving the soliton equations including the contribution of ion's motion and the finite temperature effects under the quasi-neutral approximation. In the limit of immobile ions, the RCP soliton tends to be peaked and stronger as the magnetic field increases, while the enhanced soliton becomes broader as the temperature increases. These findings in 1D model are well validated by 2D simulations.

  9. Plasma compression in magnetic reconnection regions in the solar corona

    CERN Document Server

    Provornikova, Elena; Lukin, Vyacheslav S

    2016-01-01

    It has been proposed that particles bouncing between magnetized flows converging in a reconnection region can be accelerated by the first order Fermi mechanism. Analytical considerations of this mechanism have shown that the spectral index of accelerated particles is related to the total plasma compression within the reconnection region similarly to the case of diffusive shock acceleration mechanism. As a first step to investigate the efficiency of Fermi acceleration in reconnection regions in producing hard energy spectra of particles in the solar corona, we explore the degree of plasma compression that can be achieved at reconnection sites. In particular, we aim to determine the conditions for the strong compressions to form. Using a two-dimensional resistive MHD numerical model we consider a set of magnetic field configurations where magnetic reconnection can occur including a Harris current sheet, a force-free current sheet, and two merging flux ropes. Plasma parameters are taken to be characteristic of t...

  10. Plasma transport in a simulated magnetic-divertor configuration

    Energy Technology Data Exchange (ETDEWEB)

    Strawitch, C. M.

    1981-03-01

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

  11. Nonlinear laser-plasma interaction in magnetized liner inertial fusion

    Science.gov (United States)

    Geissel, Matthias; Awe, T. J.; Bliss, D. E.; Campbell, M. E.; Gomez, M. R.; Harding, E.; Harvey-Thompson, A. J.; Hansen, S. B.; Jennings, C.; Kimmel, M. W.; Knapp, P.; Lewis, S. M.; McBride, R. D.; Peterson, K.; Schollmeier, M.; Scoglietti, D. J.; Sefkow, A. B.; Shores, J. E.; Sinars, D. B.; Slutz, S. A.; Smith, I. C.; Speas, C. S.; Vesey, R. A.; Porter, J. L.

    2016-03-01

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

  12. Nonrelativistic parallel shocks in unmagnetized and weakly magnetized plasmas

    CERN Document Server

    Niemiec, Jacek; Bret, Antoine; Wieland, Volkmar

    2012-01-01

    We present results of 2D3V particle-in-cell simulations of non-relativistic plasma collisions with absent or parallel large-scale magnetic field for parameters applicable to the conditions at young supernova remnants. We study the collision of plasma slabs of different density, leading to two different shocks and a contact discontinuity. Electron dynamics play an important role in the development of the system. While non-relativistic shocks in both unmagnetized and magnetized plasmas can be mediated by Weibel-type instabilities, the efficiency of shock-formation processes is higher when a large-scale magnetic field is present. The electron distributions downstream of the forward and reverse shocks are generally isotropic, whereas that is not always the case for the ions. We do not see any significant evidence of pre-acceleration, neither in the electron population nor in the ion distribution.

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

    Science.gov (United States)

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

    2016-10-01

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

  14. Poloidal correlation reflectometry at W7-X: radial electric field and coherent fluctuations

    Science.gov (United States)

    Windisch, T.; Krämer-Flecken, A.; Velasco, JL; Könies, A.; Nührenberg, C.; Grulke, O.; Klinger, T.; the W7-X Team

    2017-10-01

    Poloidal correlation reflectometry measurements during the first plasma campaign of the optimized stellarator Wendelstein-7X are presented. The radial electric field is determined and a comparison with neoclassical calculations and shows good qualitative agreement. The measured density fluctuation spectrum exhibits coherent low- and high-frequency modes. Magneto-hydrodynamic (MHD) modeling results suggest that the coherent fluctuations are caused by stable MHD-modes and Alfvén waves.

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

    Science.gov (United States)

    Yamada, Masaaki; Yoo, Jongsoo; Jara-Almonte, Jonathan; Ji, Hantao; Kulsrud, Russell M; Myers, Clayton E

    2014-09-10

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

  16. Magnetic Reconnection in a Compressible MHD Plasma

    Science.gov (United States)

    Hesse, Michael; Birn, Joachim; Zenitani, Seiji

    2011-01-01

    Using steady-state resistive MHD, magnetic reconnection is reinvestigated for conditions of high resistivity/low magnetic Reynolds number, when the thickness of the diffusion region is no longer small compared to its length. Implicit expressions for the reconnection rate and other reconnection parameters are derived based on the requirements of mass, momentum, and energy conservation. These expressions are solved via simple iterative procedures. Implications specifically for low Reynolds number/high resistivity are being discussed

  17. Magnetized plasma flow injection into tokamak and high-beta compact torus plasmas

    Science.gov (United States)

    Matsunaga, Hiroyuki; Komoriya, Yuuki; Tazawa, Hiroyasu; Asai, Tomohiko; Takahashi, Tsutomu; Steinhauer, Loren; Itagaki, Hirotomo; Onchi, Takumi; Hirose, Akira

    2010-11-01

    As an application of a magnetized coaxial plasma gun (MCPG), magnetic helicity injection via injection of a highly elongated compact torus (magnetized plasma flow: MPF) has been conducted on both tokamak and field-reversed configuration (FRC) plasmas. The injected plasmoid has significant amounts of helicity and particle contents and has been proposed as a fueling and a current drive method for various torus systems. In the FRC, MPF is expected to generate partially spherical tokamak like FRC equilibrium by injecting a significant amount of magnetic helicity. As a circumstantial evidence of the modified equilibrium, suppressed rotational instability with toroidal mode number n = 2. MPF injection experiments have also been applied to the STOR-M tokamak as a start-up and current drive method. Differences in the responses of targets especially relation with beta value and the self-organization feature will be studied.

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

    Science.gov (United States)

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

    2016-12-01

    A mirror-field confined compact electron cyclotron resonance (ECR) plasma source using permanent magnets was developed, aiming for the realization of high-quality plasma processings where high-density reactive species are supplied to a substrate with minimizing the ion bombardment damages. The ECR position was located between a microwave transmissive window and a quartz limiter, and plasmas were transported from the ECR position to a midplane of the magnetic mirror field through the quartz limiter. Thus, a radius of core plasma could be determined by the limiter, which was 15 mm in this study. Plasma parameters were investigated by the Langmuir probe measurement. High-density plasma larger than 1011 cm-3 could be produced by applying 5.85-GHz microwave power of 10 W or more. For the outside region of the core plasma where a wafer for plasma processings will be set at, the ion current density was decreased dramatically with distance from the core plasma and became smaller by approximately two orders of magnitude that in the core plasma region for the radial position of 40 mm, suggesting the realization of reduction in ion bombardment damages.

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

    Science.gov (United States)

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

    2016-12-01

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

  20. Photon splitting in a strongly magnetized, charge-asymmetric plasma

    Directory of Open Access Journals (Sweden)

    Chistyakov M.V.

    2016-01-01

    Full Text Available The process of the photon splitting, γ → γγ, is investigated in the presence of strongly magnetized charge-asymmetric cold plasma. The dispersion properties of photons and the new polarization selection rules are obtained in such plasma. The absorption rate of the leading photon splitting channel are calculated with taking account of the photon dispersion and wave function renormalization. In addition, a comparison of the photon splitting and the Compton scattering processes is performed.

  1. Surface-wave plasma source with magnetic multicusp fields; Multicusp jiba tojikome hyomenha plasma gen

    Energy Technology Data Exchange (ETDEWEB)

    Tsuda, M.; Ono, K.; Tsuchihashi, M.; Hanazaki, M.; Komemura, T. [Mitsubishi Electric Corp., Tokyo (Japan)

    1998-11-01

    A new-type microwave plasma source has been developed for materials processing. The plasma reactor employed a launcher of azimuthally symmetric surface waves at a frequency of 2.45 GHz and also magnetic multicusp fields around the reactor chamber walls. This configuration yielded high-density (Ne {>=} 10{sup 11}cm{sup -3}) plasmas sustained by surface waves even at low gas pressures below 10 m Torr, following easy plasma ignition by electron cyclotron resonance (ECR) discharges. Electrical and optical diagnostics were made to obtain the plasma properties in Ar. It was shown that a transition from ECR excited to surface-wave excited plasmas occurs under conditions where the plasma electron density exceeds a critical value of Ne-1 times 10{sup 11}cm{sup -3}. 21 refs., 14 figs.

  2. Alfvénic tornadoes in a magnetized plasma

    Science.gov (United States)

    Shukla, P. K.

    2013-01-01

    It is shown that three-dimensional (3D) modified-kinetic Alfvén waves (m-KAWs) in a magnetized plasma can propagate in the form of Alfvénic tornadoes characterized by plasma density whirls or magnetic flux ropes carrying orbital angular momentum. By using the two-fluid model, together with Ampère's law, we derive the wave equation for 3D m-KAWs in a magnetoplasma with me/mi ≪ β ≪ 1, where me (mi) is the electron (ion) mass, β=4πn0kB (Te+Ti)/B02, n0 the unperturbed plasma number density, kB the Boltzmann constant, Te(Te) the electron (ion) temperature, and B0 the strength of the ambient magnetic field. The 3D m-KAW equation admits solutions in the form of a Laguerre-Gauss Alfvénic vortex beam or a twisted kinetic Alfvénic wave with plasma density whirls that support the dynamics of shear Alfvénic magnetic flux ropes in plasmas.

  3. Magnetic configuration of the distant plasma sheet - ISEE 3 observations

    Science.gov (United States)

    Slavin, J. A.; Smith, E. J.; Daly, P. W.; Sanderson, T. R.; Wenzel, K.-P.; Lepping, R. P.

    1987-01-01

    The influence of the IMF orientation and magnitude and substorm activity on the magnetic configuration of the central plasma sheet at 20-240 earth radii down the geomagnetic tail is investigated on the basis of ISEE-3 data. The results are presented graphically, and high-speed antisolar bulk flows threaded by southward magnetic fields are shown to be present in the distant plasma sheet after periods of substorm activity and southward IMF Bz. The effective dayside reconnection efficiency is estimated as 25 + or - 4 percent, in good agreement with theoretical models.

  4. Slot-Antenna/Permanent-Magnet Device for Generating Plasma

    Science.gov (United States)

    Foster, John E.

    2007-01-01

    A device that includes a rectangular-waveguide/slot-antenna structure and permanent magnets has been devised as a means of generating a substantially uniform plasma over a relatively large area, using relatively low input power and a low gas flow rate. The device utilizes electron cyclotron resonance (ECR) excited by microwave power to efficiently generate plasma in a manner that is completely electrodeless in the sense that, in principle, there is no electrical contact between the plasma and the antenna. Plasmas generated by devices like this one are suitable for use as sources of ions and/or electrons for diverse material-processing applications (e.g., etching or deposition) and for ion thrusters. The absence of plasma/electrode contact essentially prevents plasma-induced erosion of the antenna, thereby also helping to minimize contamination of the plasma and of objects exposed to the plasma. Consequently, the operational lifetime of the rectangular-waveguide/ slot-antenna structure is long and the lifetime of the plasma source is limited by the lifetime of the associated charged-particle-extraction grid (if used) or the lifetime of the microwave power source. The device includes a series of matched radiating slot pairs that are distributed along the length of a plasma-source discharge chamber (see figure). This arrangement enables the production of plasma in a distributed fashion, thereby giving rise to a uniform plasma profile. A uniform plasma profile is necessary for uniformity in any electron- or ion-extraction electrostatic optics. The slotted configuration of the waveguide/ antenna structure makes the device scalable to larger areas and higher powers. All that is needed for scaling up is the attachment of additional matched radiating slots along the length of the discharge chamber. If it is desired to make the power per slot remain constant in scaling up, then the input microwave power must be increased accordingly. Unlike in prior ECR microwave plasma

  5. Phonon-plasmon interaction in magnetized inhomogeneous semiconductor quantum plasmas

    Science.gov (United States)

    Ghosh, S.; Muley, Apurva

    2016-12-01

    The phonon-plasmon interaction in a magnetized inhomogeneous semiconductor quantum plasma is reported using a quantum hydrodynamic model. A quantum modified dispersion relation is employed, which leads to an evolution expression for the gain coefficient of the acoustic wave. In the present study, quantum effects and inhomogeneity are taken into account through non-dimensional quantum parameter-H and scale length of density variation parameter-L, respectively. The effects of these parameters, as well as propagation distance z, angular frequency ω, and orientation of magnetic field θ, on gain characteristics of the acoustic wave are investigated. These investigations are made for linearly and quadratically varying density structures in the presence and the absence of the magnetic field. The results infer that the magnetic field and linearly or quadratically varying density structures would play a decisive role in deciding the gain characteristics of the acoustic wave in the inhomogeneous semiconductor quantum plasma.

  6. Magnetized plasminos in cold and hot QED plasmas

    CERN Document Server

    Sadooghi, N

    2015-01-01

    The complete quasi-particle spectrum of a magnetized electromagnetic plasma is systematically explored at zero and nonzero temperatures. To this purpose, the general structure of the one-loop corrected propagator of magnetized fermions is determined, and the dispersion relations arising from the pole of this propagator are numerically solved. It turns out that in the lowest Landau level, where only one spin direction is allowed, the spectrum consists of one positively (negatively) charged fermionic mode with positive (negative) spin. In contrast, in higher Landau levels, as an indirect consequence of the double spin degeneracy of fermions, the spectrum consists of two massless collective modes with left- and right-chiralities. The mechanism through which these new collective excitations are created in a uniform magnetic field is similar to the production mechanism of dynamical holes (plasminos) at finite temperature and zero magnetic fields. Whereas cold magnetized plasminos appear for moderate magnetic field...

  7. Magnetic null points in kinetic simulations of space plasmas

    OpenAIRE

    Olshevsky, Vyacheslav; Deca, Jan; Divin, Andrey; Peng, Ivy Bo; Markidis, Stefano; Innocenti, Maria Elena; Cazzola, Emanuele; Lapenta, Giovanni

    2015-01-01

    We present a systematic attempt to study magnetic null points and the associated magnetic energy conversion in kinetic Particle-in-Cell simulations of various plasma configurations. We address three-dimensional simulations performed with the semi-implicit kinetic electromagnetic code iPic3D in different setups: variations of a Harris current sheet, dipolar and quadrupolar magnetospheres interacting with the solar wind; and a relaxing turbulent configuration with multiple null points. Spiral n...

  8. Fast magnetic reconnection in laser-produced plasma bubbles

    OpenAIRE

    Fox, W.; Bhattacharjee, A.; Germaschewski, K.

    2011-01-01

    Recent experiments have observed magnetic reconnection in high-energy-density, laser-produced plasma bubbles, with reconnection rates observed to be much higher than can be explained by classical theory. Based on fully kinetic particle simulations we find that fast reconnection in these strongly driven systems can be explained by magnetic flux pile-up at the shoulder of the current sheet and subsequent fast reconnection via two-fluid, collisionless mechanisms. In the strong drive regime with ...

  9. Vlasov-Fokker-Planck modeling of magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Alexander [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-08-01

    Understanding the magnetic fields that can develop in high-power-laser interactions with solid-density plasma is important because such fields significantly modify both the magnitude and direction of electron heat fluxes. The dynamics of such fields evidently have consequences for inertial fusion energy applications, as the coupling of the laser beams with the walls or pellet and the development of temperature inhomogeneities are critical to the uniformity of the implosion and potentially the success of, for example, the National Ignition Facility. To study these effects, we used the code Impacta, a two-dimensional, fully implicit, Vlasov-Fokker-Planck code with self-consistent magnetic fields and a hydrodynamic ion model, designed for nanosecond time-scale laser-plasma interactions. Heat-flux effects in Ohm’s law under non-local conditions was investigated; physics that is not well captured by standard numerical models but is nevertheless important in fusion-related scenarios. Under such conditions there are numerous interesting physical effects, such as collisional magnetic instabilities, amplification of magnetic fields, re-emergence of non-locality through magnetic convection, and reconnection of magnetic field lines and redistribution of thermal energy. In this project highlights included the first full scale kinetic simulations of a magnetized hohlraum [Joglekar 2016] and the discovery of a new magnetic reconnection mechanism [Joglekar 2014] as well as a completed PhD thesis and the production of a new code for Inertial Fusion research.

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

    Science.gov (United States)

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

    2017-08-01

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

  11. Development of a new lower hybrid antenna module using a poloidal power divider

    Energy Technology Data Exchange (ETDEWEB)

    Maebara, Sunao; Seki, Masami; Suganuma, Kazuaki [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment] [and others

    1996-07-01

    The antenna using poloidal power divider is an effective method for simplification of Lower Hybrid Current Drive (LHCD) antenna system. This method should allow to reduce the power density in the antenna while maintaining a good flexibility of N{sub parallel} spectrum of waves. For this purpose, three types of poloidal power divider which split the power in three, and the 3 x 6 multi-junction module were developed. r.f. properties and outgassing of these components were evaluated using the CEA Cadarache RF Test Facility. A good power dividing ratio of 33 {+-} 4% was obtained for each of these poloidal dividers, and the reflection coefficient was lower value than 1.5%. For the 3 x 6 multi-junction, reflection coefficient was less than 1.3% and r.f. losses lower than 1.0% were measured. On the other hand, it was found in the scattering matrix analysis that reflection coefficient at plasma has to be less than a few % in order to operate these components under available conditions. In combination with two poloidal power dividers connected to the 3 x 6 multi-junction module, quasi stationary operation for r.f. injection time of 1000 sec at 300 kW was demonstrated under water cooling. In this case, it was found that the outgassing rate is in the lower range of 10{sup -7}Pam{sup 3}s{sup -1}m{sup -2} within the maximum module temperature of {approx}100degC. This report describes the experimental and analytical results of a new lower hybrid (LH) antenna module using the poloidal power divider. (author)

  12. Theoretical study of plasma confinement by magnetic multicusp field

    Science.gov (United States)

    Khalzov, Ivan; Forest, Cary

    2014-10-01

    Plasma confinement in a magnetic multicusp field is studied numerically using both collisional particle-in-cell and isothermal two-fluid MHD codes and tested against the empirical model. The simulation domain is two-dimensional, periodic in one direction and bounded by absorbing boundaries with multicups field in other direction. First, we study the dependence of plasma loss width on plasma parameters and field strength and compare the results with the well-known empirical formula w = 2√{ρeρi } (two hybrid gyro-radius). Our results show that the loss width has the same scaling with magnetic field w ~ 1 / B , but dependence on other plasma parameters does not agree with this formula. Second, we study the plasma flow drive in the cusp region due to electric field applied by discrete electrodes. The electrode positions are optimized for achieving the highest plasma flow. Comparison with available experimental data from Madison Plasma Dynamo Experiment (MPDX) is made. The work is supported by NSF and DoE.

  13. A multi-model plasma simulation of collisionless magnetic reconnection

    Science.gov (United States)

    Datta, I. A. M.; Shumlak, U.; Ho, A.; Miller, S. T.

    2016-10-01

    Collisionless magnetic reconnection is a process relevant to many areas of plasma physics in which energy stored in magnetic fields within highly conductive plasmas is rapidly converted to plasma energy. A full understanding of this phenomenon, however, is currently incomplete as models developed to date have difficulty explaining the fast reconnection rates often seen in nature, such as in the case of solar flares. Therefore, this behavior represents an area of much research in which various plasma models have been tested in order to understand the proper physics explaining the reconnection process. In this research, the WARPXM code developed at the University of Washington is used to study the problem using a hybrid multi-model simulation employing Hall-MHD and two-fluid plasma models. The simulation is performed on a decomposed domain where different plasma models are solved in different regions, depending on a trade-off between each model's physical accuracy and associated computational expense in each region. The code employs a discontinuous Galerkin (DG) finite element spatial discretization coupled with a Runge-Kutta scheme for time advancement and uses boundary conditions to couple the different plasma models. This work is supported by a Grant from the United States Air Force Office of Scientific Research.

  14. Practicality of magnetic compression for plasma density control

    Science.gov (United States)

    Gueroult, Renaud; Fisch, Nathaniel J.

    2016-03-01

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

  15. a Novel Method for Improving Plasma Nitriding Efficiency: Pre-Magnetization by DC Magnetic Field

    Science.gov (United States)

    Kovaci, Halim; Yetim, Ali Fatih; Bozkurt, Yusuf Burak; Çelik, Ayhan

    2017-06-01

    In this study, a novel pre-magnetization process, which enables easy diffusion of nitrogen, was used to enhance plasma nitriding efficiency. Firstly, magnetic fields with intensities of 1500G and 2500G were applied to the untreated samples before nitriding. After the pre-magnetization, the untreated and pre-magnetized samples were plasma nitrided for 4h in a gas mixture of 50% N2-50% H2 at 500∘C and 600∘C. The structural, mechanical and morphological properties of samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), microhardness tester and surface tension meter. It was observed that pre-magnetization increased the surface energy of the samples. Therefore, both compound and diffusion layer thicknesses increased with pre-magnetization process before nitriding treatment. As modified layer thickness increased, higher surface hardness values were obtained.

  16. Poloidal radiation asymmetries during disruption mitigation by massive gas injection on the DIII-D tokamak

    Science.gov (United States)

    Eidietis, N. W.

    2016-10-01

    Measurements of poloidal asymmetry in the radiated power during thermal quench (TQ) mitigation by massive gas injection (MGI) on DIII-D show poloidal peaking in the radiated heat flux at the wall generally consistent with 3D resistive MHD modeling, that indicates a large n=1 tearing mode causes these asymmetries. Radiation asymmetries are a concern to ITER because they can cause localized melting of the first wall even if globally the mitigation successfully radiates 100% of the plasma thermal energy. Toroidal radiation asymmetries have been well-studied, but until now the equally important poloidal asymmetries were not well constrained. Radiation emissivity profiles are reconstructed by tomographic inversion of AXUV photodiode arrays, from which the peaking measurements are derived. The poloidal peaking measurements are compared to NIMROD 3D resistive MHD simulations. Qualitatively, the measured and modeled peaking evolve similarly. In both cases, peaking during the TQ changes little with toroidal phase, consistent with predictions of n=1 MHD during the TQ producing the asymmetry. Quantitatively, the measured TQ peaking amplitudes are comparable to but consistently higher than the modeled values. This is a result of the measured radiation exhibiting high emissivity lobes at larger minor radius (and outside the separatrix) than the modeled cases, which may indicate incomplete treatment of the plasma-neutral interaction at the plasma edge in the model. This work, combined with previous measurement and modeling and toroidal radiation asymmetries, provides a basis for constraining localized mitigation radiation heat flux in ITER. Work supported by US DOE under DE-FC02-04ER54698.

  17. Microseconds-scale magnetic actuators system for plasma feedback stabilization

    Science.gov (United States)

    Kogan, K.; Be'ery, I.; Seemann, O.

    2016-10-01

    Many magnetic confinement machines use active feedback stabilization with magnetic actuators. We present a novel magnetic actuators system with a response time much faster than previous ones, making it capable of coping with the fast plasma instabilities. The system achieved a response time of 3 μs with maximal current of 500 A in a coil with inductance of 5.2 μH. The system is based on commercial solid-state switches and FPGA state machine, making it easily scalable to higher currents or higher inductivity.

  18. Magnetic plasma confinement for laser ion source.

    Science.gov (United States)

    Okamura, M; Adeyemi, A; Kanesue, T; Tamura, J; Kondo, K; Dabrowski, R

    2010-02-01

    A laser ion source (LIS) can easily provide a high current beam. However, it has been difficult to obtain a longer beam pulse while keeping a high current. On occasion, longer beam pulses are required by certain applications. For example, more than 10 micros of beam pulse is required for injecting highly charged beams to a large sized synchrotron. To extend beam pulse width, a solenoid field was applied at the drift space of the LIS at Brookhaven National Laboratory. The solenoid field suppressed the diverging angle of the expanding plasma and the beam pulse was widened. Also, it was observed that the plasma state was conserved after passing through a few hundred gauss of the 480 mm length solenoid field.

  19. Plasma Detachment Mechanisms in Propulsive Magnetic Nozzles

    Science.gov (United States)

    2013-03-07

    this research was provided by the Gobierno de Espa~na (Project AYA-2010-61699). 1E. Ahedo and M. Merino, “Two-dimensional supersonic plasma accelera...must be emphasized that they have no direct influence on the forma - tion of the QDL itself nor the magnitude of the potential jump across it, which...reprints for Governmental purpose notwithstanding any copyright notation hereon. Additional support for this research was provided by the Gobierno de

  20. Large-Area Permanent-Magnet ECR Plasma Source

    Science.gov (United States)

    Foster, John E.

    2007-01-01

    A 40-cm-diameter plasma device has been developed as a source of ions for material-processing and ion-thruster applications. Like the device described in the immediately preceding article, this device utilizes electron cyclotron resonance (ECR) excited by microwave power in a magnetic field to generate a plasma in an electrodeless (noncontact) manner and without need for an electrically insulating, microwave-transmissive window at the source. Hence, this device offers the same advantages of electrodeless, windowless design - low contamination and long operational life. The device generates a uniform, high-density plasma capable of sustaining uniform ion-current densities at its exit plane while operating at low pressure [magnetic field in this device is generated by a permanent-magnet circuit that is optimized to generate resonance surfaces. The microwave power is injected on the centerline of the device. The resulting discharge plasma jumps into a "high mode" when the input power rises above 150 W. This mode is associated with elevated plasma density and high uniformity. The large area and uniformity of the plasma and the low operating pressure are well suited for such material-processing applications as etching and deposition on large silicon wafers. The high exit-plane ion-current density makes it possible to attain a high rate of etching or deposition. The plasma potential is <3 V low enough that there is little likelihood of sputtering, which, in plasma processing, is undesired because it is associated with erosion and contamination. The electron temperature is low and does not vary appreciably with power.

  1. Studies of HED Plasmas with Self-Generated Magnetic Field

    Energy Technology Data Exchange (ETDEWEB)

    Medvedev, Mikhail [Univ. of Kansas, Lawrence, KS (United States)

    2016-02-08

    High-amplitude sub-Larmor-scale electromagnetic turbulence is ubiquitous in high-energy density environments, such as laboratory plasmas produced by high-intensity lasers, e.g., NIF, Omega-EP, Trident, and others, and in astrophysical and space plasmas, e.g., at high-Mach-number collisionless shocks in weakly magnetized plasmas upstream regions of quasi-parallel shocks, sites of magnetic reconnection and others. Studies of plasmas and turbulence in these environments are important for fusion energy sciences and the inertial confinement concept, in particular, as well as to numerous astrophysical systems such as gamma-ray bursts, supernovae blast waves, jets of quasars and active galactic nuclei, shocks in the interplanetary medium, solar flares and many more. Such turbulence can be of various origin and thus have rather different properties, from being purely magnetic (Weibel) turbulence to various types of electromagnetic turbulence (for example, whistler wave turbulence or turbulence produced by filamentation or Weibel-type streaming instability), to purely electrostatic Langmuir turbulence. In this project we use analytical and numerical tools to study the transport, radiative, and magneto-optical properties of plasmas with sub-Larmor-scale turbulence. We discovered the connection of transport/diffusion properties to certain spectral benchmark features of (jitter) radiation produced by the plasma and radiation propagation through it. All regimes, from the relativistic to non-relativistic, were thoroughly investigated and predictions were made for laboratory plasmas and astrophysical plasmas. Thus, all the tasks outlined in the proposal were fully and successfully accomplished.

  2. Performance characterization of a permanent-magnet helicon plasma thruster

    Science.gov (United States)

    Takahashi, Kazunori; Charles, Christine; Boswell, Rod

    2012-10-01

    Helicon plasma thrusters operated at a few kWs of rf power is an active area of an international research. Recent experiments have clarified part of the thrust-generation mechanisms. Thrust components which have been identified include an electron pressure inside the source region and a Lorentz force due to an electron diamagnetic drift current and a radial component of the applied magnetic field. The use of permanent magnets (PMs) instead of solenoids is one of the solutions for improving the thruster efficiency because it does not require electricity for the magnetic nozzle formation. Here the thrust imparted from a permanent-magnet helicon plasma thruster is directly measured using a pendulum thrust balance. The source consists of permanent magnet (PM) arrays, a double turn rf loop antenna powered by a 13.56 MHz rf generator and a glass source tube. The PM arrays provide a magnetic nozzle near the open exit of the source and two configurations, which have maximum field strengths of about 100 and 270 G, are tested. A thrust of 15 mN, specific impulse of 2000 sec and a thrust efficiency of 8 percent are presently obtained for 2 kW of input power, 24 sccm flow rate of argon and the stronger magnetic field configuration.

  3. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    Science.gov (United States)

    Haynes, Christopher T.; Burgess, David; Camporeale, Enrico; Sundberg, Torbjorn

    2015-01-01

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  4. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    Energy Technology Data Exchange (ETDEWEB)

    Haynes, Christopher T., E-mail: c.t.haynes@qmul.ac.uk; Burgess, David; Sundberg, Torbjorn [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Camporeale, Enrico [Multiscale Dynamics, Centrum Wiskunde and Informatica (CWI), Amsterdam (Netherlands)

    2015-01-15

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  5. Hamiltonian vortices and reconnection in a magnetized plasma

    NARCIS (Netherlands)

    Kuvshinov, B. N.; Lakhin, V. P.; Pegoraro, F.; Schep, T. J.

    1998-01-01

    Hamiltonian vortices and reconnection in magnetized plasmas are investigated analytically and numerically using a two-fluid model. The equations are written in the Lagrangian form of three fields that are advected with different velocities. This system can be considered as a generalization and exten

  6. Observations of Solitary Structures in a Magnetized, Plasma Loaded Waveguide

    DEFF Research Database (Denmark)

    Lynov, Jens-Peter; Michelsen, Poul; Pécseli, Hans;

    1979-01-01

    Two types of solitary structure were investigated experimentally and numerically in a magnetized, plasma-loaded waveguide. One was identified as an ordinary KdV soliton and its properties were investigated with particular attention to the damping by resonant particles. The other type of pulse...

  7. GUIDING OF PLASMA BY ELECTRIC FIELD AND MAGNETIC FIELD

    Institute of Scientific and Technical Information of China (English)

    ZHANG TAO; HOU JUN-DA; TANG BAO-YIN; P. K. CHU; I. G. BROWN

    2001-01-01

    The relationship between the transported ion current and the cathodic arc current is determined in a vacuum arc plasma source equipped with a curved magnetic filter. Our results suggest that the outer and inner walls of the duct interact with the plasma independently. The duct magnetic field is a critical factor of the plasma output. The duct transport efficiency is to maximize at a value of bias plate voltage in the range +10 V to +20 V, and independent (within our limit of measurement) of the magnetic field strength in the duct. The plasma flux is composed of two components:a diffusion flux in the transverse direction due to particle collisions, and a drift flux due to the ion inertia. The inner wall of the magnetic duct sees only the diffusion flux while the outer wall receives both fluxes. Thus, applying a positive potential to the outer duct wall can reflect the ions and increase the output current. Our experimental data also show that biasing both sides of the duct is more effective than biasing the outer wall alone.

  8. Interaction of a neutral cloud moving through a magnetized plasma

    Science.gov (United States)

    Goertz, C. K.; Lu, G.

    1990-01-01

    Current collection by outgassing probes in motion relative to a magnetized plasma may be significantly affected by plasma processes that cause electron heating and cross field transport. Simulations of a neutral gas cloud moving across a static magnetic field are discussed. The authors treat a low-Beta plasma and use a 2-1/2 D electrostatic code linked with the authors' Plasma and Neutral Interaction Code (PANIC). This study emphasizes the understanding of the interface between the neutral gas cloud and the surrounding plasma where electrons are heated and can diffuse across field lines. When ionization or charge exchange collisions occur a sheath-like structure is formed at the surface of the neutral gas. In that region the crossfield component of the electric field causes the electron to E times B drift with a velocity of the order of the neutral gas velocity times the square root of the ion to electron mass ratio. In addition a diamagnetic drift of the electron occurs due to the number density and temperature inhomogeneity in the front. These drift currents excite the lower-hybrid waves with the wave k-vectors almost perpendicular to the neutral flow and magnetic field again resulting in electron heating. The thermal electron current is significantly enhanced due to this heating.

  9. Spark plasma sintering of Mn-Al-C hard magnets.

    Science.gov (United States)

    Pasko, A; LoBue, M; Fazakas, E; Varga, L K; Mazaleyrat, F

    2014-02-12

    Structural and magnetic characterization of isotropic Mn-Al-C bulk samples obtained by spark plasma sintering (SPS) is reported. This technique, to the best of our knowledge, has not been used for preparation of Mn-Al-based permanent magnets previously. Transformation from the parent -phase to the ferromagnetic τ-phase occurred on heating in the process of sintering. The phase constitution of the melt-spun precursors and consolidated samples was determined by x-ray diffraction. Magnetic hysteresis loops were recorded using a vibrating sample magnetometer. The compositional dependence of the coercivity, magnetization and density of the sintered materials is analysed. To combine good magnetic properties with proper densification, further optimization of the production parameters is necessary.

  10. Dynamics of whistler spheromaks in magnetized plasmas.

    Science.gov (United States)

    Eliasson, B; Shukla, P K

    2007-11-16

    Recent laboratory experiments [Stenzel et al., Phys. Rev. Lett. 96, 095004 (2006)10.1103/PhysRevLett.96.095004] have demonstrated interesting phenomena of propagating nonlinear whistler structures (spheromaks) and stationary field-reversed configurations, whose magnetic fields exceed the ambient magnetic field strength. Our objective here is to present simulation studies for these nonlinear whistler structures based on the three-dimensional nonlinear electron magnetohydrodynamic equations. The robustness and longevity of the propagating whistler spheromaks found in the experiments are confirmed numerically. Varying the toroidal field of the spheromak in the initial conditions, we find that the polarity and the amplitude of the toroidal field determine the propagation direction and speed of the spheromak. Our simulation results are in excellent agreement with those observed in the laboratory experiments.

  11. Low-frequency fluctuations in a pure toroidal magnetized plasma

    Indian Academy of Sciences (India)

    P K Sharma; R Singh; D Bora

    2009-12-01

    A magnetized, low- plasma in pure toroidal configuration is formed and extensively studied with ion mass as control parameter. Xenon, krypton and argon plasmas are formed at a fixed toroidal magnetic field of 0.024 T, with a peak density of ∼ 1011 cm-3, ∼ 4 × 1010 cm-3 and ∼ 2 × 1010 cm−3 respectively. The experimental investigation of time-averaged plasma parameter reveals that their profiles remain insensitive to ion mass and suggests that saturated slab equilibrium is obtained. Low-frequency (LF) coherent fluctuations ( < ci) are observed and identified as flute modes. Here ci represents ion cyclotron frequency. Our results indicate that these modes get reduced with ion mass. The frequency of the fluctuating mode decreases with increase in the ion mass. Further, an attempt has been made to discuss the theory of flute modes to understand the relevance of some of our experimental observations.

  12. Plasma transport induced by the stochastic magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kubota, Tetsuyuki [Interdisciplinary Graduate School of Engineering Sciences, Kyushu Univ., Kasuga, Fukuoka (Japan); Itoh, Sanae-I.; Yagi, Masatoshi

    1998-10-01

    The anomalous plasma transport induced by the stochastic magnetic field is studied to understand the disruption phenomena in the tokamak plasma. At first, the transport matrix which indicate the plasma transport in the stochastic magnetic field is formulated. For the formulation, the quasi-linear approximation for the diffusivity of the stochastic magnetic field is used and the shifted Maxwellian is assumed to the particle distribution. Using this transport matrix the radial electric field formation, which is generated by the ambipolar condition, and the associated temperature profile is obtained. The temperature profile in the stochastic magnetic field becomes flat because of the rapid temperature diffusion. Next the temperature crash, i.e., the sawtooth oscillation and the giant ELM, is analyzed using the turbulence-turbulence transition model, which describes the transition between the state of the electrostatic turbulence and that of the electromagnetic turbulence. This transition has a hysteresis characteristics. When the state changes to the electromagnetic mode, the stochastic magnetic field appears and the temperature transport is enhanced. This transition model is included in the 1-D transport equation. To calculate this transport equation numerically the crash of the temperature profile and the propagation of the crash front (avalanche) are realized by this model. The collapse without a precursor oscillation is revealed. (author)

  13. The Plasma Instrument for Magnetic Sounding (PIMS) for the Europa Mission

    Science.gov (United States)

    Westlake, J. H.; McNutt, R. L.; Kasper, J. C.; Case, A. W.; Rymer, A. M.; Stevens, M. L.; Jia, X.; Paty, C.; Khurana, K. K.; Kivelson, M. G.; Slavin, J. A.; Smith, H. T.; Korth, H.; Krupp, N.; Roussous, E.; Saur, J.

    2016-10-01

    We present the Plasma Instrument for Magnetic Sounding (PIMS) selected for the Europa Mission. We specifically address how PIMS plasma measurements will improve the accuracy of magnetic sounding of Europa's subsurface ocean.

  14. Laser Plasmas : Density oscillations in laser produced plasma decelerated by external magnetic field

    Indian Academy of Sciences (India)

    V N Rai; M Shukla; H C Pant

    2000-11-01

    This paper presents the dynamics as well as the stability of laser produced plasma expanding across the magnetic field. Observation of some high frequency fluctuations superimposed on ion saturation current along with structuring in the pin hole images of x-ray emitting plasma plume indicate the presence of instability in the plasma. Two type of slope in the variation of x-ray emission with laser intensity in the absence and presence of magnetic field shows appearance of different threshold intensity of laser corresponding to each magnetic field at which this instability or density fluctuation sets on. This instability has been identified as a large Larmor radius instability instead of classical Rayleigh-Taylor (R-T) instability.

  15. Electromagnetic Emission from Laser Wakefields in Magnetized Underdense Plasmas

    Institute of Scientific and Technical Information of China (English)

    胡志丹; 盛政明; 丁文君; 王伟民; 董全力; 张杰

    2012-01-01

    A wakefield driven by a short intense laser pulse in a perpendicularly magnetized underdense plasma is studied analytically and numerically for both weakly relativistic and highly relativistic situations. Owing to the DC magnetic field, a transverse component of the electric fields associated with the wakefield appears, while the longitudinal wave is not greatly affected by the magnetic field up to 22 Tesla. Moreover, the scaling law of the transverse field versus the longitudinal field is derived. One-dimensional particle-in-cell simulation results confirm the analytical results. Wakefield transmission through the plasma-vacuum boundary, where electromagnetic emission into vacuum occurs, is also investigated numerically. These results are useful for the generation of terahertz radiation and the diagnosis of laser wakefields.

  16. Plasma Equilibrium in a Magnetic Field with Stochastic Regions

    Energy Technology Data Exchange (ETDEWEB)

    J.A. Krommes and Allan H. Reiman

    2009-04-23

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

  17. Electron vortex magnetic holes: a nonlinear coherent plasma structure

    CERN Document Server

    Haynes, Christopher T; Camporeale, Enrico; Sundberg, Torbjorn

    2014-01-01

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional PIC simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is ...

  18. Topology of magnetic helicity of torsioned filaments in Hall plasmas

    CERN Document Server

    de Andrade, L C Garcia

    2007-01-01

    A solution of magnetic Hall equations for plasma filaments in the Coulomb gauge is obtained in the non-holonomic frame. Some physical features of the solution include, the non-conservation of the magnetic helicity and the decay of the magnetic field in the filaments. From the mathematical point of view,the presence of Frenet torsion in the filament is actually shown to be fundamental for the breaking of conservation of magnetic helicity in the case of helicoidal filaments. Since the magnetic helicity is not conserved even in the Coulomb gauge, and the magnetic field decays, one can say that the dynamo action fails. Actually the presence of torsion enhances the breaking of magnetic field helicity conservation. A similar formula of the one obtained here without considering the Hall effect has been obtained by Moffatt and Ricca (PRSA-1992) in the case of holonomic filaments. It is shown that unknotted magnetic filaments may place a lower bound on the magnetic energy. Discussions on the writhe number are also dis...

  19. Study on spatial distribution of plasma parameters in a magnetized inductively coupled plasma

    Energy Technology Data Exchange (ETDEWEB)

    Cheong, Hee-Woon; Lee, Woohyun; Kim, Ji-Won; Whang, Ki-Woong, E-mail: kwhang@snu.ac.kr [Plasma Laboratory, Inter-University Semiconductor Research Center, Department of Electrical and Computer Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of); Kim, Hyuk [Samsung Electronics Co., Banwol-dong, Hwaseong 445-701 (Korea, Republic of); Park, Wanjae [Tokyo Electron Miyagi Ltd., Taiwa-cho, Kurokawa-gun, Miyagi 981-3629 (Japan)

    2015-07-15

    Spatial distributions of various plasma parameters such as plasma density, electron temperature, and radical density in an inductively coupled plasma (ICP) and a magnetized inductively coupled plasma (M-ICP) were investigated and compared. Electron temperature in between the rf window and the substrate holder of M-ICP was higher than that of ICP, whereas the one just above the substrate holder of M-ICP was similar to that of ICP when a weak (<8 G) magnetic field was employed. As a result, radical densities in M-ICP were higher than those in ICP and the etch rate of oxide in M-ICP was faster than that in ICP without severe electron charging in 90 nm high aspect ratio contact hole etch.

  20. Poloidal rotation of main ions in the CT-6B tokamak

    Institute of Scientific and Technical Information of China (English)

    冯春华; 李赞良; 杨宣宗; 郑少白; 李文莱; 王龙

    2003-01-01

    The poloidal rotation velocity of neutral hydrogen atoms is measured using the Doppler shift of the Hα spectral line emitted in the CT-6B tokamak. The poloidal rotation of hydrogen atoms is generated through the collisions and charge-exchanges with main ions (protons). Therefore, the rotation direction of main ions can be deduced from that of neutral hydrogen atoms. The experimental results show that the main ions rotate in the electron diamagnetic drift direction, the same as the impurity ions, in the plasma core. The neutral hydrogen atoms rotate also in the electron diamagnetic drift direction in the edge region of the plasma. However, the rotation direction of main ions in the edge region cannot be judged from the experimental result due to the long mean free path of hydrogen atoms in the edge region. An inward diffusion flux of hydrogen atoms toward the torus inside with a velocity of the same order of magnitude as their poloidal rotation is also observed.

  1. Corrosion behavior of magnetic ferrite coating prepared by plasma spraying

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi; Wei, Shicheng, E-mail: wsc33333@163.com; Tong, Hui; Tian, Haoliang; Liu, Ming; Xu, Binshi

    2014-12-15

    Graphical abstract: The saturation magnetization (M{sub s}) of the ferrite coating is 34.417 emu/g while the M{sub s} value of the ferrite powder is 71.916 emu/g. It can be seen that plasma spray process causes deterioration of the room temperature soft magnetic properties. - Highlights: • Spinel ferrite coatings have been prepared by plasma spraying. • The coating consists of nanocrystalline grains. • The saturation magnetization of the ferrite coating is 34.417 emu/g. • Corrosion behavior of the ferrite coating was examined in NaCl solution. - Abstract: In this study, spray dried spinel ferrite powders were deposited on the surface of mild steel substrate through plasma spraying. The structure and morphological studies on the ferrite coatings were carried out using X-ray diffraction, scanning electron microscope and Raman spectroscopy. It was showed that spray dried process was an effective method to prepare thermal spraying powders. The coating showed spinel structure with a second phase of LaFeO{sub 3}. The magnetic property of the ferrite samples were measured by vibrating sample magnetometer. The saturation magnetization (M{sub s}) of the ferrite coating was 34.417 emu/g. The corrosion behavior of coating samples was examined by electrochemical impedance spectroscopy. EIS diagrams showed three corrosion processes as the coating immersed in 3.5 wt.% NaCl solution. The results suggested that plasma spraying was a promising technology for the production of magnetic ferrite coatings.

  2. Degenerate mixing of plasma waves on cold, magnetized single-species plasmas

    Science.gov (United States)

    Anderson, M. W.; O'Neil, T. M.; Dubin, D. H. E.; Gould, R. W.

    2011-10-01

    In the cold-fluid dispersion relation ω =ωp/[1+(k⊥/kz)2]1/2 for Trivelpiece-Gould waves on an infinitely long magnetized plasma cylinder, the transverse and axial wavenumbers appear only in the combination k⊥/kz. As a result, for any frequency ω Dubin modes), a perturbation analysis is used to investigate the mixing of low-order, nearly degenerate Dubin modes caused by small deformations of a plasma spheroid.

  3. Effects of pulsed electric field on ULQ and RFP plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, M. [Iwate Univ., Morioka (Japan). Faculty of Engineering; Saito, K.; Suzuki, T. [and others

    1997-12-31

    Dynamo activity and self-organization processes are investigated using the application of pulsed poloidal and toroidal electric fields on ULQ and RFP plasmas. Synchronized to the application of the pulsed electric fields, the remarkable responses of the several plasma parameters are observed. The plasma has a preferential magnetic field structure, and the external perturbation activates fluctuation to maintain the structure through dynamo effect. This process changes the total dissipation with the variation of magnetic helicity in the system, showing that self organization accompanies an enhanced dissipation. (author)

  4. A linear radio frequency plasma reactor for potential and current mapping in a magnetized plasma.

    Science.gov (United States)

    Faudot, E; Devaux, S; Moritz, J; Heuraux, S; Molina Cabrera, P; Brochard, F

    2015-06-01

    Langmuir probe measurements in front of high power ion cyclotron resonant frequency antennas are not possible or simply too noisy to be analyzed properly. A linear experiment is a radio frequency (RF) magnetized plasma discharge reactor designed to probe the rectified potential in front of such antennas but at low power level (1 kW) to next improve antenna design and mitigate sheath effects. The maximum magnetic field is 0.1 T, and the RF amplifier can work between 10 kHz and 250 MHz allowing ion cyclotron resonances for argon or helium. The first measurements with no magnetic field are presented here, especially 2D potential maps extracted from the RF compensated probe measurements yield ni ≈ 10(15) m(-3) and Te ≈ 2 eV for RF power lower than 100 W. Series resonances in the chamber are highlighted and allow to deduce the plasma parameters from a simple equivalent impedance model of the plasma in helium gas. Next studies will be focused on magnetized plasmas and especially magnetized RF sheaths.

  5. A 7 T Pulsed Magnetic Field Generator for Magnetized Laser Plasma Experiments

    Science.gov (United States)

    Hu, Guangyue; Liang, Yihan; Song, Falun; Yuan, Peng; Wang, Yulin; Zhao, Bin; Zheng, Jian

    2015-02-01

    A pulsed magnetic field generator was developed to study the effect of a magnetic field on the evolution of a laser-generated plasma. A 40 kV pulsed power system delivered a fast (~230 ns), 55 kA current pulse into a single-turn coil surrounding the laser target, using a capacitor bank of 200 nF, a laser-triggered switch and a low-impedance strip transmission line. A one-dimensional uniform 7 T pulsed magnetic field was created using a Helmholtz coil pair with a 6 mm diameter. The pulsed magnetic field was controlled to take effect synchronously with a nanosecond heating laser beam, a femtosecond probing laser beam and an optical Intensified Charge Coupled Device (ICCD) detector. The preliminary experiments demonstrate bifurcation and focusing of plasma expansion in a transverse magnetic field.

  6. Magnetic Yang-Mills Theory of the Gluon Plasma

    CERN Document Server

    Baker, M

    2009-01-01

    We propose magnetic SU(N) pure gauge theory as an effective field theory describing the long distance nonperturbative magnetic response of the deconfined phase of Yang-Mills theory. The magnetic non-Abelian Lagrangian, unlike that of electrodynamics where there is exact electromagnetic duality, is not known explicitly, but here we regard the magnetic SU(N) Yang-Mills Lagrangian as the leading term in the long distance effective gauge theory of the plasma phase. In this treatment, which is applicable for a range of temperatures in the interval T_c < T < 3 T_c accessible in heavy ion experiments, formation of the magnetic energy profile around a spatial Wilson loop in the deconfined phase parallels the formation of an electric flux tube in the confined phase. We use the effective theory to calculate spatial Wilson loops and the magnetic charge density induced in the plasma by the corresponding color electric current loops. These calculations suggest that the deconfined phase of Yang-Mills theory has the p...

  7. MAGNETIC NULL POINTS IN KINETIC SIMULATIONS OF SPACE PLASMAS

    Energy Technology Data Exchange (ETDEWEB)

    Olshevsky, Vyacheslav; Innocenti, Maria Elena; Cazzola, Emanuele; Lapenta, Giovanni [Centre for Mathematical Plasma Astrophysics (CmPA), KU Leuven (Belgium); Deca, Jan [Laboratory for Atmospheric and Space Physics (LASP), University of Colorado Boulder, Boulder, CO (United States); Divin, Andrey [St. Petersburg State University, St. Petersburg (Russian Federation); Peng, Ivy Bo; Markidis, Stefano, E-mail: sya@mao.kiev.ua [High Performance Computing and Visualization (HPCViz), KTH Royal Institute of Technology, Stockholm (Sweden)

    2016-03-01

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

  8. The acoustic instabilities in magnetized collisional dusty plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, B. P., E-mail: birendra.pandey@mq.edu.au [Department of Physics and Astrophysics, Macquarie University, Sydney, NSW 2109 (Australia); Vladimirov, S. V., E-mail: s.vladimirov@physics.usyd.edu.au [Metamaterials Laboratory, National Research University of Information Technology, Mechanics, and Optics, St. Petersburg 199034 (Russian Federation); Dwivedi, C. B., E-mail: jagatpurdwivedi@gmail.com [Ved–Vijnanam Pravartanam Samitihi, Pratapgarh (Awadh), Jagatpur, Bharat (India)

    2014-09-15

    The present work investigates the wave propagation in collisional dusty plasmas in the presence of electric and magnetic field. It is shown that the dust ion-acoustic waves may become unstable to the reactive instability whereas dust-acoustic waves may suffer from both reactive and dissipative instabilities. If the wave phase speed is smaller than the plasma drift speed, the instability is of reactive type whereas in the opposite case, the instability becomes dissipative in nature. Plasma in the vicinity of dust may also become unstable to reactive instability with the instability sensitive to the dust material: dielectric dust may considerably quench this instability. This has implications for the dust charging and the use of dust as a probe in the plasma sheath.

  9. Dielectric effects on Thomson scattering in a relativistic magnetized plasma

    DEFF Research Database (Denmark)

    Bindslev, H.

    1991-01-01

    the absorption is small. Symmetry between variables relating to incident and scattered fields is demonstrated and shown to be in agreement with the reciprocity relation. Earlier results are confirmed in the cold plasma limit. Significant relativistic effects, of practical importance to the scattering......The effects of the dielectric properties of a relativistic magnetized plasma on the scattering of electromagnetic radiation by fluctuations in electron density are investigated. The origin of the density fluctuations is not considered. Expressions for the scattering cross-section and the scattered...... power accepted by the receiving antenna are derived for a plasma with spatial dispersion. The resulting expressions allow thermal motion to be included in the description of the plasma and remain valid for frequencies of the probing radiation in the region of omega(p) and omega(ce), provided...

  10. Ultra-High Intensity Magnetic Field Generation in Dense Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Fisch, Nathaniel J. [Princeton Univ., NJ (United States)

    2014-01-08

    The main objective of this grant proposal was to explore the efficient generation of intense currents. Whereas the efficient generation of electric current in low-­energy-­density plasma has occupied the attention of the magnetic fusion community for several decades, scant attention has been paid to carrying over to high-­energy-­density plasma the ideas for steady-­state current drive developed for low-­energy-­density plasma, or, for that matter, to inventing new methodologies for generating electric current in high-­energy-­density plasma. What we proposed to do was to identify new mechanisms to accomplish current generation, and to assess the operation, physics, and engineering basis of new forms of current drive in regimes appropriate for new fusion concepts.

  11. Ultra-High Intensity Magnetic Field Generation in Dense Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Fisch, Nathaniel J

    2014-01-08

    I. Grant Objective The main objective of this grant proposal was to explore the efficient generation of intense currents. Whereasthefficient generation of electric current in low-­energy-­density plasma has occupied the attention of the magnetic fusion community for several decades, scant attention has been paid to carrying over to high-­energy-­density plasma the ideas for steady-­state current drive developed for low-­energy-­density plasma, or, for that matter, to inventing new methodologies for generating electric current in high-­energy-­density plasma. What we proposed to do was to identify new mechanisms to accomplish current generation, and to assess the operation, physics, and engineering basis of new forms of current drive in regimes appropriate for new fusion concepts.

  12. An integrated approach to the control of magnetically confined plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Albanese, R.; Ambrosino, G.; Ariola, M.; Bagatin, M.; Bellina, F.; Bettini, P.; Borghi, C.A.; Chitarin, G.; Coccorese, E.; Formisano, A.; Fresa, R.; De Magistris, M.; Gnesotto, F.; Guarnieri, M.; Marchiori, G.; Martone, R.; Pironti, A.; Ribani, P.L.; Rubinacci, G.; Stella, A. E-mail: stella@uniud.it; Trevisan, F.; Villone, F

    2001-10-01

    In this paper, a short review of the work done in the framework of a nation-wide research programme on 'Models and Methods for Plasma Control in Magnetically Confined Fusion Experiments' is presented. The broad aim of the overall programme is to develop and propose a new effective and reliable approach to the on-line plasma control for future fusion experiments, starting from the today's theoretical background, validated by experimental evidence from a number of tests performed on existing experiments. The proposed formulation to approach the control problem is a linearized model in terms of suitable state variables and input/output relationships. The basic project has been subdivided into four major areas of investigation: the linearized response plasma model, the three-dimensional electromagnetic model, the identification techniques and finally the plasma control requirements. The most remarkable results, achieved so far in each area above, are presented in the paper.

  13. Effective magnetization of the dust particles in a complex plasma

    Science.gov (United States)

    Kählert, Hanno

    2012-10-01

    The large mass and size of the dust particles in a complex plasma has several advantages, including low characteristic frequencies on the order of a few Hz and the ability to record their motion with video cameras. However, these properties pose major difficulties for achieving strong magnetization. While the light electrons and ions can be magnetized by (superconducting) magnets, magnetizing the heavy dust component is extremely challenging. Instead of further increasing the magnetic field strengths or decreasing the particle size, we use the analogy between the Lorentz force and the Coriolis force experienced by particles in a rotating reference frame to create ``effective magnetic fields'' which is a well-established technique in the field of trapped quantum gases [1]. To induce rotation in a complex plasma, we take advantage of the neutral drag force, which allows to transmit the motion of a rotating neutral gas to the dust particles [2]. The equations of motion in the rotating frame agree with those in a stationary gas except for the additional centrifugal and Coriolis forces [3]. Due to the slow rotation frequencies (˜ Hz) and contrary to the situation in a strong magnetic field, only the properties of the heavy dust particles are notably affected. Experiments with a rotating electrode realize the desired velocity profile for the neutral gas and allow us to verify the efficiency of the concept [3].[4pt] This work was performed in collaboration with J. Carstensen, M. Bonitz, H. L"owen, F. Greiner, and A. Piel.[4pt] [1] A. L. Fetter, Rev. Mod. Phys. 81, 647 (2009)[0pt] [2] J. Carstensen, F. Greiner, L.-J. Hou, H. Maurer, and A. Piel, Phys. Plasmas 16, 013702 (2009)[0pt] [3] H. K"ahlert, J. Carstensen, M. Bonitz, H. L"owen, F. Greiner, and A. Piel, submitted for publication, arXiv:1206.5073

  14. Magnetic stochasticity in magnetically confined fusion plasmas chaos of field lines and charged particle dynamics

    CERN Document Server

    Abdullaev, Sadrilla

    2014-01-01

    This is the first book to systematically consider the modern aspects of chaotic dynamics of magnetic field lines and charged particles in magnetically confined fusion plasmas.  The analytical models describing the generic features of equilibrium magnetic fields and  magnetic perturbations in modern fusion devices are presented. It describes mathematical and physical aspects of onset of chaos, generic properties of the structure of stochastic magnetic fields, transport of charged particles in tokamaks induced by magnetic perturbations, new aspects of particle turbulent transport, etc. The presentation is based on the classical and new unique mathematical tools of Hamiltonian dynamics, like the action--angle formalism, classical perturbation theory, canonical transformations of variables, symplectic mappings, the Poincaré-Melnikov integrals. They are extensively used for analytical studies as well as for numerical simulations of magnetic field lines, particle dynamics, their spatial structures and  statisti...

  15. Spatial and temporal characteristics of poloidal waves in the terrestrial plasmasphere: a CLUSTER case study

    Directory of Open Access Journals (Sweden)

    S. Schäfer

    2007-05-01

    Full Text Available Oscillating magnetic field lines are frequently observed by spacecraft in the terrestrial and other planetary magnetospheres. The CLUSTER mission is a very suitable tool to further study these Alfvén waves as the four CLUSTER spacecraft provide for an opportunity to separate spatial and temporal structures in the terrestrial magnetosphere. Using a large scaled configuration formed by the four spacecraft we are able to detect a poloidal Ultra-Low-Frequency (ULF pulsation of the magnetic and electric field in order to analyze its temporal and spatial structures. For this purpose the measurements are transformed into a specific field line related coordinate system to investigate their specific amplitude pattern depending on the path of the CLUSTER spacecraft across oscillating field lines. These measurements are then compared with modeled spacecraft observations across a localized poloidal wave resonator in the dayside plasmasphere. A detailed investigation of theoretically expected poloidal eigenfrequencies allows us to specify the observed 16 mHz pulsation as a third harmonic oscillation. Based on this we perform a case study providing a clear identification of wave properties such as an spatial scale structure of about 0.67 RE, the azimuthal wave number m≈30, temporal evolution, and energy transport in the detected ULF pulsations.

  16. A method for estimating tokamak poloidal field coil currents which incorporates engineering constraints

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, W.A.

    1990-05-01

    This thesis describes the development of a design tool for the poloidal field magnet system of a tokamak. Specifically, an existing program for determining the poloidal field coil currents has been modified to: support the general case of asymmetric equilibria and coil sets, determine the coil currents subject to constraints on the maximum values of those currents, and determine the coil currents subject to limits on the forces those coils may carry. The equations representing the current limits and coil force limits are derived and an algorithm based on Newton's method is developed to determine a set of coil currents which satisfies those limits. The resulting program allows the designer to quickly determine whether or not a given coil set is capable of supporting a given equilibrium. 25 refs.

  17. Scaling mechanisms of vapour/plasma shielding from laser-produced plasmas to magnetic fusion regimes

    Science.gov (United States)

    Sizyuk, Tatyana; Hassanein, Ahmed

    2014-02-01

    The plasma shielding effect is a well-known mechanism in laser-produced plasmas (LPPs) reducing laser photon transmission to the target and, as a result, significantly reducing target heating and erosion. The shielding effect is less pronounced at low laser intensities, when low evaporation rate together with vapour/plasma expansion processes prevent establishment of a dense plasma layer above the surface. Plasma shielding also loses its effectiveness at high laser intensities when the formed hot dense plasma plume causes extensive target erosion due to radiation fluxes back to the surface. The magnitude of emitted radiation fluxes from such a plasma is similar to or slightly higher than the laser photon flux in the low shielding regime. Thus, shielding efficiency in LPPs has a peak that depends on the laser beam parameters and the target material. A similar tendency is also expected in other plasma-operating devices such as tokamaks of magnetic fusion energy (MFE) reactors during transient plasma operation and disruptions on chamber walls when deposition of the high-energy transient plasma can cause severe erosion and damage to the plasma-facing and nearby components. A detailed analysis of these abnormal events and their consequences in future power reactors is limited in current tokamak reactors. Predictions for high-power future tokamaks are possible only through comprehensive, time-consuming and rigorous modelling. We developed scaling mechanisms, based on modelling of LPP devices with their typical temporal and spatial scales, to simulate tokamak abnormal operating regimes to study wall erosion, plasma shielding and radiation under MFE reactor conditions. We found an analogy in regimes and results of carbon and tungsten erosion of the divertor surface in ITER-like reactors with erosion due to laser irradiation. Such an approach will allow utilizing validated modelling combined with well-designed and well-diagnosed LPP experimental studies for predicting

  18. Magnetic field amplification by collisionless shocks in partially ionized plasmas

    CERN Document Server

    Ohira, Yutaka

    2015-01-01

    In this paper, we study shock structures of collisionless shocks in partially ionized plasmas by means of two-dimensional hybrid simulations, where the shock is a perpendicular shock with shock velocity Vsh ~ 40 Va ~ 1333 km/s and the upstream ionization fraction is 0.5. We find that large density fluctuations and large magnetic fields fluctuations are generated both in the upstream and downstream regions. In addition, we find that the velocity distribution of downstream hydrogen atoms has three components. Observed shock structures suggest that diffusive shock acceleration can operate at perpendicular shocks propagating into partially ionized plasmas in real three-dimensional systems.

  19. Plasma structures inside boundary layers of magnetic clouds

    Institute of Scientific and Technical Information of China (English)

    WEI Fengsi; FENG Xueshang; YANG Fang; ZHONG Dingkun

    2004-01-01

    We analyze the plasma structures for 50 magnetic cloud boundary layers (BLs) which were observed by the spacecraft WIND from February, 1995 to June 2003. Main discoveries are: (ⅰ) The BL is a non-pressure balanced structure, its total pressure, PT,L, (the thermal pressure, Pth,L, plus the magnetic pressure, PM,L) is generally less than the total pressure PT,S and PT,C of the front solar wind (SW) and the following magnetic clouds (MC), respectively. The rising of the Pth,L inside the BLs is often not enough to compensate the declining of PM,L; (ⅱ) The ratio of electron and proton temperatures, (Te/Tp)L, inside the BLs is offen less than (Te/Tp)s and (Te/Tp)c in the SW and the MC, respectively, because the heating of proton is more obvious than that of electron; and (ⅲ) The reversal jet is observed in 80% BLs investigated, in which the reversal jets from all of three directions (±Vx, ±Vy, ±Vz), were observed in ≈25% BLs. These basic characteristics could be associated with a possible magnetic reconnection process inside the BLs. The results above suggest that the cloud BL owns the plasma structures different from those in the SW and MC. It is a manifestation for the existing significant dynamic interaction between the magnetic cloud and the solar wind.

  20. Magnetic null points in kinetic simulations of space plasmas

    CERN Document Server

    Olshevsky, Vyacheslav; Divin, Andrey; Peng, Ivy Bo; Markidis, Stefano; Innocenti, Maria Elena; Cazzola, Emanuele; Lapenta, Giovanni

    2015-01-01

    We present a systematic attempt to study magnetic null points and the associated magnetic energy conversion in kinetic Particle-in-Cell simulations of various plasma configurations. We address three-dimensional simulations performed with the semi-implicit kinetic electromagnetic code iPic3D in different setups: variations of a Harris current sheet, dipolar and quadrupolar magnetospheres interacting with the solar wind; and a relaxing turbulent configuration with multiple null points. Spiral nulls are more likely created in space plasmas: in all our simulations except lunar magnetic anomaly and quadrupolar mini-magnetosphere the number of spiral nulls prevails over the number of radial nulls by a factor of 3-9. We show that often magnetic nulls do not indicate the regions of intensive energy dissipation. Energy dissipation events caused by topological bifurcations at radial nulls are rather rare and short-lived. The so-called X-lines formed by the radial nulls in the Harris current sheet and lunar magnetic ano...

  1. Toward the Theory of Turbulence in Magnetized Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Boldyrev, Stanislav [University of Wisconsin - Madison

    2013-07-26

    The goal of the project was to develop a theory of turbulence in magnetized plasmas at large scales, that is, scales larger than the characteristic plasma microscales (ion gyroscale, ion inertial scale, etc.). Collisions of counter-propagating Alfven packets govern the turbulent cascade of energy toward small scales. It has been established that such an energy cascade is intrinsically anisotropic, in that it predominantly supplies energy to the modes with mostly field-perpendicular wave numbers. The resulting energy spectrum of MHD turbulence, and the structure of the fluctuations were studied both analytically and numerically. A new parallel numerical code was developed for simulating reduced MHD equations driven by an external force. The numerical setting was proposed, where the spectral properties of the force could be varied in order to simulate either strong or weak turbulent regimes. It has been found both analytically and numerically that weak MHD turbulence spontaneously generates a “condensate”, that is, concentration of magnetic and kinetic energy at small k{sub {parallel}}. A related topic that was addressed in the project is turbulent dynamo action, that is, generation of magnetic field in a turbulent flow. We were specifically concentrated on the generation of large-scale magnetic field compared to the scales of the turbulent velocity field. We investigate magnetic field amplification in a turbulent velocity field with nonzero helicity, in the framework of the kinematic Kazantsev-Kraichnan model.

  2. Fast magnetic reconnection in laser-produced plasma bubbles.

    Science.gov (United States)

    Fox, W; Bhattacharjee, A; Germaschewski, K

    2011-05-27

    Recent experiments have observed magnetic reconnection in high-energy-density, laser-produced plasma bubbles, with reconnection rates observed to be much higher than can be explained by classical theory. Based on fully kinetic particle simulations we find that fast reconnection in these strongly driven systems can be explained by magnetic flux pileup at the shoulder of the current sheet and subsequent fast reconnection via two-fluid, collisionless mechanisms. In the strong drive regime with two-fluid effects, we find that the ultimate reconnection time is insensitive to the nominal system Alfvén time.

  3. Modeling of Stark–Zeeman Lines in Magnetized Hydrogen Plasmas

    Indian Academy of Sciences (India)

    J. Rosato; H. Bufferand; H. Capes; M. Koubiti; L. Godbert-Mouret; Y. Marandet; R. Stamm

    2015-12-01

    The action of electric and magnetic fields on atomic species results in a perturbation of the energy level structure, which alters the shape of spectral lines. In this work, we present the Zeeman–Stark line shape simulation method and perform new calculations of hydrogen Lyman and Balmer lines, in the framework of magnetic fusion research. The role of the Zeeman effect, fine structure and the plasma's non-homogeneity along the line-of-sight are investigated. Under specific conditions, our results are applicable to DA white dwarf atmospheres.

  4. Equilibrium Reconstructions with V3FIT and Current Evolution Modeling for 3-D Stellarator Plasmas

    Science.gov (United States)

    Schmitt, J. C.; Cianciosa, M.; Geiger, J.; Lazerson, S.

    2016-10-01

    V3FIT is a powerful equilibrium reconstruction tool for magnetic confinement fusion experiments which are inherently 3-D in nature (i.e. stellarators) or have 3-D components (tokamaks with 3-D shaping, reversed field pinches with helical states, etc). Here, we present details of the diagnostic modeling, constraints and the user interface for reconstructions of W7-X plasmas. For typical discharges during the OP1.1 run campaign of W7-X, the net toroidal current and current density profile do not reach steady-state. When modeling the current evolution in 3-D plasmas, both poloidal and toroidal currents are linked with both poloidal and toroidal fluxes. In contrast, in toroidally axisymmetric plasmas, the poloidal flux is linked only with the toroidal current and the toroidal current is linked only with the poloidal flux. Compared to an equivalently-sized axisymmetric configuration, the current diffusion in 3-D plasmas is enhanced, leading to a faster relaxation of the current profile to its steady-state. Implications for the time-evolution of the current and rotational transform profiles in stellarator plasmas are discussed. This work is supported by DoE Grant DE-SC00014529.

  5. New mode of operating a magnetized coaxial plasma gun for injecting magnetic helicity into a spheromak.

    Science.gov (United States)

    Woodruff, S; Hill, D N; Stallard, B W; Bulmer, R; Cohen, B; Holcomb, C T; Hooper, E B; McLean, H S; Moller, J; Wood, R D

    2003-03-07

    By operating a magnetized coaxial plasma gun continuously with just sufficient current to enable plasma ejection, large gun-voltage spikes (approximately 1 kV) are produced, giving the highest sustained voltage approximately 500 V and highest sustained helicity injection rate observed in the Sustained Spheromak Physics Experiment. The spheromak magnetic field increases monotonically with time, exhibiting the lowest fluctuation levels observed during formation of any spheromak (B/B>/=2%). The results suggest an important mechanism for field generation by helicity injection, namely, the merging of helicity-carrying filaments.

  6. Magnetic compressibility and ion-temperature-gradient-driven microinstabilities in magnetically confined plasmas

    CERN Document Server

    Zocco, A; Connor, J W

    2015-01-01

    The electromagnetic theory of the strongly driven ion-temperature-gradient (ITG) instability in magnetically confined toroidal plasmas is developed. Stabilizing and destabilizing effects are identified, and a critical $\\beta_{e}$ (the ratio of the electron to magnetic pressure) for stabilization of the toroidal branch of the mode is calculated for magnetic equilibria independent of the coordinate along the magnetic field. Its scaling is $\\beta_{e}\\sim L_{Te}/R,$ where $L_{Te}$ is the characteristic electron temperature gradient length, and $R$ the major radius of the torus. We conjecture that a fast particle population can cause a similar stabilization due to its contribution to the equilibrium pressure gradient. For sheared equilibria, the boundary of marginal stability of the electromagnetic correction to the electrostatic mode is also given. For a general magnetic equilibrium, we find a critical length (for electromagnetic stabilization) of the extent of the unfavourable curvature along the magnetic field....

  7. Acoustic solitons in magnetized quantum electron-positron plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Mahmood, S; Akhtar, N; Ur-Rehman, H, E-mail: shahzadm100@gmail.com [Theoretical Plasma Physics Division (TPPD), PINSTECH, PO Nilore, Islamabad 44000 (Pakistan)

    2011-03-15

    Nonlinear acoustic wave propagation in dense magnetized electron-positron (e-p) plasmas in the presence of ions is studied. The e-p quantum fluid is taken to be dynamic, while the ions are assumed to be stationary to neutralize the plasma background only. The quantum hydrodynamics model is employed and the reductive perturbation method is used to derive the Zakharov-Kuznetsov equation. Electrostatic potential hump structures are obtained and it is found that an increase in positron concentration decreases the wave amplitude. However, an increase in magnetic field strength reduces the width of the structure significantly. The numerical results are also shown for illustration; the parameters used are taken from the data for the outer layers of white dwarfs.

  8. Nonlinear electrostatic wave equations for magnetized plasmas - II

    DEFF Research Database (Denmark)

    Dysthe, K. B.; Mjølhus, E.; Pécseli, H. L.

    1985-01-01

    For pt.I see ibid., vol.26, p.443-7 (1984). The problem of extending the high frequency part of the Zakharov equations for nonlinear electrostatic waves to magnetized plasmas, is considered. Weak electromagnetic and thermal effects are retained on an equal footing. Direction dependent (electrosta......For pt.I see ibid., vol.26, p.443-7 (1984). The problem of extending the high frequency part of the Zakharov equations for nonlinear electrostatic waves to magnetized plasmas, is considered. Weak electromagnetic and thermal effects are retained on an equal footing. Direction dependent...... (electrostatic) cut-off implies that various cases must be considered separately, leading to equations with rather different properties. Various equations encountered previously in the literature are recovered as limiting cases....

  9. Magnetic field generation and amplification in an expanding plasma

    CERN Document Server

    Schoeffler, K M; Fonseca, R A; Silva, L O

    2013-01-01

    Particle-in-cell simulations are used to investigate the formation of magnetic fields, B, in plasmas with perpendicular electron density and temperature gradients. For system sizes, L, comparable to the ion skin depth, d_i, it is shown that B ~ d_i/L, consistent with the Biermann battery effect. However, for large L/d_i, it is found that the Weibel instability (due to electron temperature anisotropy) supersedes the Biermann battery as the main producer of B. The Weibel-produced fields saturate at a finite amplitude (plasma \\beta \\approx 100), independent of L. The magnetic energy spectra below the electron Larmor radius scale is well fitted by power law with slope -16/3, as predicted in Schekochihin et al., Astrophys. J. Suppl. Ser 182, 310 (2009).

  10. Magnetic field advection in two interpenetrating plasma streams

    Energy Technology Data Exchange (ETDEWEB)

    Ryutov, D. D.; Kugland, N. L.; Levy, M. C.; Plechaty, C.; Ross, J. S.; Park, H. S. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

    2013-03-15

    Laser-generated colliding plasma streams can serve as a test-bed for the study of various astrophysical phenomena and the general physics of self-organization. For streams of a sufficiently high kinetic energy, collisions between the ions of one stream with the ions of the other stream are negligible, and the streams can penetrate through each other. On the other hand, the intra-stream collisions for high-Mach-number flows can still be very frequent, so that each stream can be described hydrodynamically. This paper presents an analytical study of the effects that these interpenetrating streams have on large-scale magnetic fields either introduced by external coils or generated in the plasma near the laser targets. Specifically, a problem of the frozen-in constraint is assessed and paradoxical features of the field advection in this system are revealed. A possibility of using this system for studies of magnetic reconnection is mentioned.

  11. Scaling of Magnetic Reconnection in Relativistic Collisionless Pair Plasmas

    Science.gov (United States)

    Liu, Yi-Hsin; Guo, Fan; Daughton, William; Li, Hui; Hesse, Michael

    2015-01-01

    Using fully kinetic simulations, we study the scaling of the inflow speed of collisionless magnetic reconnection in electron-positron plasmas from the non-relativistic to ultra-relativistic limit. In the anti-parallel configuration, the inflow speed increases with the upstream magnetization parameter sigma and approaches the speed of light when sigma is greater than O(100), leading to an enhanced reconnection rate. In all regimes, the divergence of the pressure tensor is the dominant term responsible for breaking the frozen-in condition at the x-line. The observed scaling agrees well with a simple model that accounts for the Lorentz contraction of the plasma passing through the diffusion region. The results demonstrate that the aspect ratio of the diffusion region, modified by the compression factor of proper density, remains approximately 0.1 in both the non-relativistic and relativistic limits.

  12. Instabilities, turbulence and transport in a magnetized plasma; Instabilites, turbulence et transport dans un plasma magnetise

    Energy Technology Data Exchange (ETDEWEB)

    Garbet, X

    2001-06-01

    The purpose of this work is to introduce the main processes that occur in a magnetized plasma. During the last 2 decades, the understanding of turbulence has made great progress but analytical formulas and simulations are far to produce reliable predictions. The values of transport coefficients in a tokamak plasma exceed by far those predicted by the theory of collisional transport. This phenomenon is called abnormal transport and might be due to plasma fluctuations. An estimation of turbulent fluxes derived from the levels of fluctuations, is proposed. A flow description of plasma allows the understanding of most micro-instabilities. The ballooning representation deals with instabilities in a toric geometry. 3 factors play an important role to stabilize plasmas: density pinch, magnetic shear and speed shear. The flow model of plasma gives an erroneous value for the stability threshold, this is due to a bad description of the resonant interaction between wave and particle. As for dynamics, flow models can be improved by adding dissipative terms so that the linear response nears the kinetic response. The kinetic approach is more accurate but is complex because of the great number of dimensions involved. (A.C.)

  13. GPUbased, Microsecond Latency, HectoChannel MIMO Feedback Control of Magnetically Confined Plasmas

    Science.gov (United States)

    Rath, Nikolaus

    Feedback control has become a crucial tool in the research on magnetic confinement of plasmas for achieving controlled nuclear fusion. This thesis presents a novel plasma feedback control system that, for the first time, employs a Graphics Processing Unit (GPU) for microsecond-latency, real-time control computations. This novel application area for GPU computing is opened up by a new system architecture that is optimized for low-latency computations on less than kilobyte sized data samples as they occur in typical plasma control algorithms. In contrast to traditional GPU computing approaches that target complex, high-throughput computations with massive amounts of data, the architecture presented in this thesis uses the GPU as the primary processing unit rather than as an auxiliary of the CPU, and data is transferred from A-D/D-A converters directly into GPU memory using peer-to-peer PCI Express transfers. The described design has been implemented in a new, GPU-based control system for the High-Beta Tokamak - Extended Pulse (HBT-EP) device. The system is built from commodity hardware and uses an NVIDIA GeForce GPU and D-TACQ A-D/D-A converters providing a total of 96 input and 64 output channels. The system is able to run with sampling periods down to 4 μs and latencies down to 8 μs. The GPU provides a total processing power of 1.5 x 1012 floating point operations per second. To illustrate the performance and versatility of both the general architecture and concrete implementation, a new control algorithm has been developed. The algorithm is designed for the control of multiple rotating magnetic perturbations in situations where the plasma equilibrium is not known exactly and features an adaptive system model: instead of requiring the rotation frequencies and growth rates embedded in the system model to be set a priori, the adaptive algorithm derives these parameters from the evolution of the perturbation amplitudes themselves. This results in non-linear control

  14. Riemannian geometrical constraints on magnetic vortex filaments in plasmas

    OpenAIRE

    de Andrade, L. C. Garcia

    2005-01-01

    Two theorems on the Riemannian geometrical constraints on vortex magnetic filaments acting as dynamos in (MHD) flows are presented. The use of Gauss-Mainard-Codazzi equations allows us to investigate in detail the influence of curvature and torsion of vortex filaments in the MHD dynamos. This application follows closely previous applications to Heisenberg spin equation to the investigations in magnetohydrostatics given by Schief (Plasma Physics J. 10, 7, 2677 (2003)). The Lorentz force on vor...

  15. Currents between tethered electrodes in a magnetized laboratory plasma

    Science.gov (United States)

    Stenzel, R. L.; Urrutia, J. M.

    1989-01-01

    Laboratory experiments on important plasma physics issues of electrodynamic tethers were performed. These included current propagation, formation of wave wings, limits of current collection, nonlinear effects and instabilities, charging phenomena, and characteristics of transmission lines in plasmas. The experiments were conducted in a large afterglow plasma. The current system was established with a small electron-emitting hot cathode tethered to an electron-collecting anode, both movable across the magnetic field and energized by potential difference up to V approx.=100 T(sub e). The total current density in space and time was obtained from complete measurements of the perturbed magnetic field. The fast spacecraft motion was reproduced in the laboratory by moving the tethered electrodes in small increments, applying delayed current pulses, and reconstructing the net field by a linear superposition of locally emitted wavelets. With this technique, the small-amplitude dc current pattern is shown to form whistler wings at each electrode instead of the generally accepted Alfven wings. For the beam electrode, the whistler wing separates from the field-aligned beam which carries no net current. Large amplitude return currents to a stationary anode generate current-driven microinstabilities, parallel electric fields, ion depletions, current disruptions and time-varying electrode charging. At appropriately high potentials and neutral densities, excess neutrals are ionized near the anode. The anode sheath emits high-frequency electron transit-time oscillations at the sheath-plasma resonance. The beam generates Langmuir turbulence, ion sound turbulence, electron heating, space charge fields, and Hall currents. An insulated, perfectly conducting transmission line embedded in the plasma becomes lossy due to excitation of whistler waves and magnetic field diffusion effects. The implications of the laboratory observations on electrodynamic tethers in space are discussed.

  16. Co-current toroidal rotation-driven and turbulent stresses with resonant magnetic perturbations in the edge plasmas of the J-TEXT tokamak

    Science.gov (United States)

    Zhao, K. J.; Shi, Yuejiang; Liu, H.; Diamond, P. H.; Li, F. M.; Cheng, J.; Chen, Z. P.; Nie, L.; Ding, Y. H.; Wu, Y. F.; Chen, Z. Y.; Rao, B.; Cheng, Z. F.; Gao, L.; Zhang, X. Q.; Yang, Z. J.; Wang, N. C.; Wang, L.; Jin, W.; Xu, J. Q.; Yan, L. W.; Dong, J. Q.; Zhuang, G.; J-TEXT Team

    2016-07-01

    The acceleration of the co-current toroidal rotations around resonant surfaces by resonant magnetic perturbations (RMPs) through turbulence is presented. These experiments were performed using a Langmuir probe array in the edge plasmas of the J-TEXT tokamak. This study aims at understanding the RMP effects on edge toroidal rotations and exploring its control method. With RMPs, the flat electron temperature T e profile, due to magnetic islands, appears around resonant surfaces (Zhao et al 2015 Nucl. Fusion 55 073022). When the resonant surface is closer to the last closed flux surface, the flat T e profile vanishes with RMPs. In both cases, the toroidal rotations significantly increase in the direction of the plasma current around the resonant surfaces with RMPs. The characteristics of turbulence are significantly affected by RMPs around the resonant surfaces. The turbulence intensity profile changes and the poloidal wave vector k θ increases with RMPs. The power fraction of the turbulence components in the ion diamagnetic drift direction increases with RMPs. The measurements of turbulent Reynolds stresses are consistent with the toroidal flows that can be driven by turbulence. The estimations of the energy transfer between the turbulence and toroidal flows suggest that turbulence energy transfers into toroidal flows. The result has the implication of the intrinsic rotation being driven by RMPs via turbulence.

  17. Multi-channel poloidal correlation reflectometry on experimental advanced superconducting tokamak

    Science.gov (United States)

    Qu, H.; Zhang, T.; Han, X.; Xiang, H. M.; Wen, F.; Geng, K. N.; Wang, Y. M.; Kong, D. F.; Cai, J. Q.; Huang, C. B.; Gao, Y.; Gao, X.; Zhang, S.

    2016-11-01

    A new multi-channel poloidal correlation reflectometry is developed at Experimental Advanced Superconducting Tokamak. Eight dielectric resonator oscillators with frequencies of 12.5 GHz, 13.5 GHz, 14.5 GHz, 15 GHz, 15.5 GHz, 16 GHz, 17 GHz, and 18 GHz are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together. The output waves are launched by one single antenna after passing through a 20 dB directional coupler which can provide the reference signal. Two poloidally separated antennae are installed to receive the reflected waves from plasma. The reference and reflected signals are down-converted by mixing with a quadrupled signal from a phase-locked source with a frequency of 14.2 GHz and the IF signals pass through the filter bank. The resulting signals from the mixers are detected by I/Q demodulators. The setup enables the measurement of density fluctuation at 8 (radial) × 2 (poloidal) spatial points. A coherent mode with an increasing velocity from 50 kHz to 100 kHz is observed by using the system. The mode is located in the steep gradient region of the pedestal.

  18. Toroidal and poloidal soft x-ray imaging system on the DIII-D tokamak

    Science.gov (United States)

    Snider, R. T.; Evanko, R.; Haskovec, J.

    1988-08-01

    A toroidal soft x-ray imaging system is being added to the currently installed poloidal soft x-ray system on the DIII-D tokamak. The poloidal array is used to determine the poloidal mode structure and location of internal helical MHD perturbations in the plasma. The new array will add toroidal mode identification capability. The four detector arrays are toroidally spaced in a manner that allows identification of toroidal mode numbers up to 24. Beryllium vacuum windows separate the detectors from the tokamak vacuum and also serve as low-energy filters. The separate detector vacuum chambers can be filled with a gas that changes the low-energy cutoff of the system. By proper selection of the gas and pressure the low-energy cutoff can be chosen over the entire range of the detector sensitivity (500-1200 eV). This capability can be used to produce crude x-ray spectra for the entire imaging system or for gain control.

  19. Toroidal and poloidal soft X-ray imaging system on the D3-D tokamak

    Science.gov (United States)

    Snider, R.; Evanko, R.; Haskovec, J.

    1988-02-01

    A toroidal soft X-ray imaging system is being added to the currently installed poloidal soft X-ray system on the D3-D tokamak. The poloidal array is used to determine the poloidal mode structure and location of internal helical MHD perturbations in the plasma. The new array will add toroidal mode identification capability. The four detector arrays are toroidally spaced in a manner which allows identification of toroidal mode numbers of up to 24. Beryllium vacuum windows separate the detectors from the tokamak vacuum and also serve as low energy filters. The separate detector vacuum chambers can be filled with a gas which changes the low energy cutoff of the system. By proper selection of the gas and pressure the low energy cutoff can be chosen over the entire range of the detector sensitivity (500 eV to 1200 eV). This capability can be used to produce crude X-ray spectra for the entire imaging system or for gain control.

  20. Dust Particle Dynamics in The Presence of Highly Magnetized Plasmas

    Science.gov (United States)

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

    2016-10-01

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

  1. Fast Magnetic Reconnection: Bridging Laboratory and Space Plasma Physics

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharjee, Amitava [University New Hampshire- Durham

    2012-02-16

    Recent developments in experimental and theoretical studies of magnetic reconnection hold promise for providing solutions to outstanding problems in laboratory and space plasma physics. Examples include sawtooth crashes in tokamaks, substorms in the Earth’s Magnetosphere, eruptive solar flares, and more recently, fast reconnection in laser-produced high energy density plasmas. In each of these examples, a common and long-standing challenge has been to explain why fast reconnection proceeds rapidly from a relatively quiescent state. In this talk, we demonstrate the advantages of viewing these problems and their solutions from a common perspective. We focus on some recent, surprising discoveries regarding the role of secondary plasmoid instabilities of thin current sheets. Nonlinearly, these instabilities lead to fast reconnection rates that are very weakly dependent on the Lundquist number of the plasma.

  2. In situ ``artificial plasma'' calibration of tokamak magnetic sensors

    Science.gov (United States)

    Shiraki, D.; Levesque, J. P.; Bialek, J.; Byrne, P. J.; DeBono, B. A.; Mauel, M. E.; Maurer, D. A.; Navratil, G. A.; Pedersen, T. S.; Rath, N.

    2013-06-01

    A unique in situ calibration technique has been used to spatially calibrate and characterize the extensive new magnetic diagnostic set and close-fitting conducting wall of the High Beta Tokamak-Extended Pulse (HBT-EP) experiment. A new set of 216 Mirnov coils has recently been installed inside the vacuum chamber of the device for high-resolution measurements of magnetohydrodynamic phenomena including the effects of eddy currents in the nearby conducting wall. The spatial positions of these sensors are calibrated by energizing several large in situ calibration coils in turn, and using measurements of the magnetic fields produced by the various coils to solve for each sensor's position. Since the calibration coils are built near the nominal location of the plasma current centroid, the technique is referred to as an "artificial plasma" calibration. The fitting procedure for the sensor positions is described, and results of the spatial calibration are compared with those based on metrology. The time response of the sensors is compared with the evolution of the artificial plasma current to deduce the eddy current contribution to each signal. This is compared with simulations using the VALEN electromagnetic code, and the modeled copper thickness profiles of the HBT-EP conducting wall are adjusted to better match experimental measurements of the eddy current decay. Finally, the multiple coils of the artificial plasma system are also used to directly calibrate a non-uniformly wound Fourier Rogowski coil on HBT-EP.

  3. Plasma cleaning of ITER first mirrors in magnetic field

    CERN Document Server

    Moser, Lucas; Leipold, Frank; Reichle, Roger; Marot, Laurent; Meyer, Ernst

    2014-01-01

    To avoid reflectivity losses in ITER optical diagnostic systems, plasma sputtering of metallic First Mirrors is foreseen in order to remove deposits coming from the main wall (mainly beryllium and tungsten). Therefore plasma cleaning has to work on large mirrors (up to a size of 200*300 mm) and under the influence of strong magnetic fields (several Tesla). This work presents the results of plasma cleaning of aluminium and aluminium oxide (used as beryllium proxy) deposited on molybdenum mirrors. Using radio frequency (13.56 MHz) argon plasma, the removal of a 260 nm mixed aluminium/aluminium oxide film deposited by magnetron sputtering on a mirror (98 mm diameter) was demonstrated. 50 nm of pure aluminium oxide were removed from test mirrors (25 mm diameter) in a magnetic field of 0.35 T for various angles between the field lines and the mirrors surfaces. The cleaning efficiency was evaluated by performing reflectivity measurements, Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy.

  4. Plasma cleaning of ITER First Mirrors in magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Moser, Lucas, E-mail: lucas.moser@unibas.ch [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Steiner, Roland [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Leipold, Frank; Reichle, Roger [ITER Organization, Route de Vinon-sur-Verdon, 13115 St Paul-lez-Durance (France); Marot, Laurent; Meyer, Ernst [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

    2015-08-15

    To avoid reflectivity losses in ITER’s optical diagnostic systems, plasma sputtering of metallic First Mirrors is foreseen in order to remove deposits coming from the main wall (mainly beryllium and tungsten). Therefore plasma cleaning has to work on large mirrors (up to a size of 200 × 300 mm) and under the influence of strong magnetic fields (several Tesla). This work presents the results of plasma cleaning of aluminium and aluminium oxide (used as beryllium proxy) deposited on molybdenum mirrors. Using radio frequency (13.56 MHz) argon plasma, the removal of a 260 nm mixed aluminium/aluminium oxide film deposited by magnetron sputtering on a mirror (98 mm diameter) was demonstrated. 50 nm of pure aluminium oxide were removed from test mirrors (25 mm diameter) in a magnetic field of 0.35 T for various angles between the field lines and the mirrors surfaces. The cleaning efficiency was evaluated by performing reflectivity measurements, Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy.

  5. Laboratory study of avalanches in a magnetized plasma

    Science.gov (United States)

    van Compernolle, Bart

    2015-11-01

    Results of a basic heat transport experiment [] involving an off-axis heat source are presented. Experiments are performed in the Large Plasma Device (LAPD) at UCLA. A ring-shaped electron beam source injects low energy electrons (below ionization energy) along a strong magnetic field into a preexisting, large and cold plasma. The injected electrons are thermalized by Coulomb collisions within a short distance and provide an off-axis heat source that results in a long, hollow, cylindrical region of elevated electron temperature embedded in a colder plasma, and far from the machine walls. It is demonstrated that this heating configuration provides an ideal environment to study avalanche phenomena under controlled conditions. The avalanches are identified as sudden rearrangements of the pressure profile following the growth of fluctuations from ambient noise. The intermittent collapses of the plasma pressure profile are associated with unstable drift-Alfvén waves and exhibit both radial and azimuthal dynamics. After each collapse the plasma enters a quiescent phase in which the pressure profile slowly recovers and steepens until a threshold is exceeded, and the process repeats. The use of reference probes as time markers allows for the visualization of the 2D spatio-temporal evolution of the avalanche events. Avalanches are only observed for a limited combination of heating powers and magnetic fields. At higher heating powers the system transitions from the avalanche regime into a regime dominated by sustained drift-Alfvén wave activity. The pressure profile then transitions to a near steady-state in which anomalous transport balances the external pressure source. Performed at the Basic Plasma Science Facility at UCLA, supported jointly by DOE and NSF.

  6. Strongly coupled non-Abelian plasmas in a magnetic field

    CERN Document Server

    Critelli, Renato

    2016-01-01

    In this dissertation we use the gauge/gravity duality approach to study the dynamics of strongly coupled non-Abelian plasmas. Ultimately, we want to understand the properties of the quark-gluon plasma (QGP), whose scientifc interest by the scientific community escalated exponentially after its discovery in the 2000's through the collision of ultrarelativistic heavy ions. One can enrich the dynamics of the QGP by adding an external field, such as the baryon chemical potential (needed to study the QCD phase diagram), or a magnetic field. In this dissertation, we choose to investigate the magnetic effects. Indeed, there are compelling evidences that strong magnetic fields of the order $eB\\sim 10 m_\\pi^2$ are created in the early stages of ultrarelativistic heavy ion collisions. The chosen observable to scan possible effects of the magnetic field on the QGP was the viscosity, due to the famous result $\\eta/s=1/4\\pi$ obtained via holography. In a first approach we use a caricature of the QGP, the $\\mathcal{N}=4$ s...

  7. Hall MHD Stability and Turbulence in Magnetically Accelerated Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    H. R. Strauss

    2012-11-27

    The object of the research was to develop theory and carry out simulations of the Z pinch and plasma opening switch (POS), and compare with experimental results. In the case of the Z pinch, there was experimental evidence of ion kinetic energy greatly in excess of the ion thermal energy. It was thought that this was perhaps due to fine scale turbulence. The simulations showed that the ion energy was predominantly laminar, not turbulent. Preliminary studies of a new Z pinch experiment with an axial magnetic field were carried out. The axial magnetic is relevant to magneto - inertial fusion. These studies indicate the axial magnetic field makes the Z pinch more turbulent. Results were also obtained on Hall magnetohydrodynamic instability of the POS.

  8. Magnetic apatite for structural insights on the plasma membrane.

    Science.gov (United States)

    Stanca, Sarmiza E; Müller, Robert; Dellith, Jan; Nietzsche, Sandor; Stöckel, Stephan; Biskup, Christoph; Deckert, Volker; Krafft, Christoph; Popp, Jürgen; Fritzsche, Wolfgang

    2015-01-21

    The iron oxide-hydroxyapatite (FeOxHA) nanoparticles reported here differ from those reported before by their advantage of homogeneity and simple preparation; moreover, the presence of carboxymethyldextran (CMD), together with hydroxyapatite (HA), allows access to the cellular membrane, which makes our magnetic apatite unique. These nanoparticles combine magnetic behavior, Raman label ability and the property of interaction with the cellular membrane; they therefore represent an interesting material for structural differentiation of the cell membrane. It was observed by Raman spectroscopy, scanning electron microscopy (SEM) and fluorescence microscopy that FeOxHA adheres to the plasma membrane and does not penetrate the membrane. These insights make the nanoparticles a promising material for magnetic cell sorting, e.g. in microfluidic device applications.

  9. Magnetic apatite for structural insights on the plasma membrane

    Science.gov (United States)

    Stanca, Sarmiza E.; Müller, Robert; Dellith, Jan; Nietzsche, Sandor; Stöckel, Stephan; Biskup, Christoph; Deckert, Volker; Krafft, Christoph; Popp, Jürgen; Fritzsche, Wolfgang

    2015-01-01

    The iron oxide-hydroxyapatite (FeOxHA) nanoparticles reported here differ from those reported before by their advantage of homogeneity and simple preparation; moreover, the presence of carboxymethyldextran (CMD), together with hydroxyapatite (HA), allows access to the cellular membrane, which makes our magnetic apatite unique. These nanoparticles combine magnetic behavior, Raman label ability and the property of interaction with the cellular membrane; they therefore represent an interesting material for structural differentiation of the cell membrane. It was observed by Raman spectroscopy, scanning electron microscopy (SEM) and fluorescence microscopy that FeOxHA adheres to the plasma membrane and does not penetrate the membrane. These insights make the nanoparticles a promising material for magnetic cell sorting, e.g. in microfluidic device applications.

  10. Pulsating jet-like structures in magnetized plasma

    Science.gov (United States)

    Goncharov, V. P.; Pavlov, V. I.

    2016-08-01

    The formation of pulsating jet-like structures has been studied in the scope of the nonhydrostatic model of a magnetized plasma with horizontally nonuniform density. We discuss two mechanisms which are capable of stopping the gravitational spreading appearing to grace the Rayleigh-Taylor instability and to lead to the formation of stationary or oscillating localized structures. One of them is caused by the Coriolis effect in the rotating frames, and another is connected with the Lorentz effect for magnetized fluids. Magnetized jets/drops with a positive buoyancy must oscillate in transversal size and can manifest themselves as "radio pulsars." The estimates of their frequencies are made for conditions typical for the neutron star's ocean.

  11. Relationship between Magnetic Helicity Injection and Magnetic Reconnection in Double-Null Startup of the UTST Spherical Tokamak

    Science.gov (United States)

    Watanabe, Takenori; Kamio, Shuji; Cao, Qinghong; Itagaki, Hirotomo; Takemura, Koichiro; Yamasaki, Kotaro; Ishiguchi, Koji; Yamada, Takuma; Inomoto, Michiaki; Ono, Yasushi

    2012-10-01

    Magnetic helicity injection is a useful idea for explaining plasma current drive and startup of various magnetized plasmas such as Spherical Tokamaks (STs). Magnetic reconnection is directly related with the magnetic helicity injection, because it is essential to reorganization of magnetic field lines injected externally. We address how and why helicity injection is related with magnetic reconnection. An ST plasma is produced by using two pairs of external poloidal field coils in the University of Tokyo Spherical Tokamak (UTST) device. In the late phase of the formation, a single ST is connected to the coil flux, which enables magnetic helicity injection from the helicity source (the coil flux) into the helicity sink (the ST plasma). We measured the Y-shaped reconnection region between the ST plasma and the poloidal coil using two dimensional pickup coil arrays in the r-z plane. magnetic reconnection of common flux into private flux causes concentration of current density along the current sheet, forming a high eigen-value area between the helicity source and the helicity sink. We made a parameter scan to study how crucial and effective the plasmoid ejection is for helicity injection and found that the plasmoid motion is a dynamic helicity injection process.

  12. Effect of Substrate Potential on Plasma Parameters of Magnetic Multicusp Plasma Source

    Science.gov (United States)

    Ueda, Yoshio; Goto, Masahiro

    1998-06-01

    The effect of substrate potential on plasmas produced in a magnetic multicusp plasma source has been studied experimentally. Plasma parameters such as electron temperature and plasma potential are estimated from electron energy distribution function numerically calculated from probe current-voltage characteristics. For a substrate potential of -150 V with respect to the source chamber, which is much lower than substrate floating potentials, the plasma parameters are not affected by the application of the potential. However, for the case where the substrate is shorted with the source chamber, the high energy component of electrons significantly decreases in comparison with the floating case leading to the reduction of electron temperature. In this case, plasma potential is positive with respect to the substrate to suppress electron loss but its absolute value is only of the order of electron temperature in eV, which is much lower than the potential between the plasma and the substrate in the floating case. This discharge mode could be advantageous in significantly reducing the ion impact energy to the substrate plate.

  13. Diffusive, convective and Nernst-effect losses of magnetic flux and heat from a wall-confined magnetized plasma

    Science.gov (United States)

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

    2013-10-01

    The recently proposed MAGLIF approach to inertial fusion ignition involves compression and heating of plasma with frozen-in magnetic flux by a heavy cylindrical liner. To reach fusion conditions, the compressed plasma should retain a large fraction of the magnetic flux and thermal energy enclosed by the liner. Magnetic flux and heat losses from strongly magnetized plasma to a cold liner wall are significantly influenced by the Nernst and Ettingshausen thermomagnetic effects. We present exact analytical solutions of 1D MHD equations with Ohmic heating, heat conductivity and thermomagnetic terms included and discuss relative roles of diffusive, conductive and Nernst-effect-related losses of magnetic flux and heat from the magnetized plasma to the wall. These solutions are compared to our 1D simulation results. They can serve for verification of plasma transport modeling by MHD codes. Work supported by DOE/NNSA.

  14. Determination of structure tilting in magnetized plasmas - Time delay estimation in two dimensions

    CERN Document Server

    Guszejnov, Dávid; Zoletnik, Sándor; Andreas-Krämer-Flecken,

    2013-01-01

    Time delay estimation (TDE) is a well-known technique to investigate poloidal flows in fusion plasmas. The present work is an extension of the earlier works of A. Bencze and S. Zoletnik 2005 and B. T\\'al et al. 2011. From the prospective of the comparison of theory and experiment it seem to be important to estimate the statistical properties of the TDE based on solid mathematical groundings. This paper provides analytic derivation of the variance of the TDE using a two-dimensional model for coherent turbulent structures in the plasma edge and also gives an explicit method for determination of the tilt angle of structures. As a demonstration this method is then applied to the results of a quasi-2D Beam Emission Spectroscopy (BES) measurement performed at the TEXTOR tokamak.

  15. 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.

  16. Mechanical impacts of poloidal eddy currents on the continuous vacuum vessel of a tokamak

    Energy Technology Data Exchange (ETDEWEB)

    In, Sang Ryul; Yoon, Byung Joo

    1996-11-01

    Poloidal eddy currents are induced on the continuous torus vacuum vessel by changes of the toroidal field during the machine start-up (toroidal field coil charge), shut-down (toroidal field coil discharge) and plasma disruption (plasma diamagnetism change). Analytic forms for the eddy currents flowing on the vessel, consequent pressures and forces acting on it are presented in this report. The results are applied to typical operation modes of the KT-2 tokamak. Stress analysis for two typical operation modes of toroidal field damping during a machine shut-gown and plasma energy quench during a plasma disruption were carried out using 3D FEM code (ANSYS 5.2). (author). 5 tabs., 22 figs., 9 refs.

  17. A poloidal field control system based on VxWorks in HT-7 Tokamak

    Institute of Scientific and Technical Information of China (English)

    WANG Feng; LUO Jia-Rong; WANG Hua-Zhong

    2004-01-01

    The PF (Poloidal Field) control system is one of the most important control systems in HT-7 Tokamak.Most of parameters such as plasma current, plasma horizontal position and plasma vertical position will be monitored.For the purpose of long-pulse discharge and the more precise control to plasma, the real-time operation system VxWorks is applied, instead of the behindhand and unbefitting DOS operation system. This paper describes the development process of HT-7 PF control system based on VxWorks on Intel X86 platforms. The method of using hardware cards in VxWorks, and the network communication with other operation systems are discussed especially. Results of the comparison between VxWorks and DOS operation systems are given too.

  18. A laboratory study of asymmetric magnetic reconnection in strongly driven plasmas.

    Science.gov (United States)

    Rosenberg, M J; Li, C K; Fox, W; Igumenshchev, I; Séguin, F H; Town, R P J; Frenje, J A; Stoeckl, C; Glebov, V; Petrasso, R D

    2015-02-04

    Magnetic reconnection, the annihilation and rearrangement of magnetic fields in a plasma, is a universal phenomenon that frequently occurs when plasmas carrying oppositely directed field lines collide. In most natural circumstances, the collision is asymmetric (the two plasmas having different properties), but laboratory research to date has been limited to symmetric configurations. In addition, the regime of strongly driven magnetic reconnection, where the ram pressure of the plasma dominates the magnetic pressure, as in several astrophysical environments, has also received little experimental attention. Thus, we have designed the experiments to probe reconnection in asymmetric, strongly driven, laser-generated plasmas. Here we show that, in this strongly driven system, the rate of magnetic flux annihilation is dictated by the relative flow velocities of the opposing plasmas and is insensitive to initial asymmetries. In addition, out-of-plane magnetic fields that arise from asymmetries in the three-dimensional plasma geometry have minimal impact on the reconnection rate, due to the strong flows.

  19. Laboratory experiments on plasma jets in a magnetic field using high-power lasers

    Directory of Open Access Journals (Sweden)

    Nishio K.

    2013-11-01

    Full Text Available The experiments to simulate astrophysical jet generation are performed using Gekko XII (GXII HIPER laser system at the Institute of Laser Engineering. In the experiments a fast plasma flow generated by shooting a CH plane (10 μm thickness is observed at the rear side of the plane. By separating the focal spot of the main beams, a non-uniform plasma is generated. The non-uniform plasma flow in an external magnetic field (0.2∼0.3 T perpendicular to the plasma is more collimated than that without the external magnetic field. The plasma β, the ratio between the plasma and magnetic pressure, is ≫ 1, and the magnetic Reynolds number is ∼150 in the collimated plasma. It is considered that the magnetic field is distorted by the plasma flow and enhances the jet collimation.

  20. Laboratory experiments on plasma jets in a magnetic field using high-power lasers

    Science.gov (United States)

    Nishio, K.; Sakawa, Y.; Kuramitsu, Y.; Morita, T.; Ide, T.; Kuwada, M.; Koga, M.; Kato, T.; Norimatsu, T.; Gregory, C.; Woolsey, N.; Murphy, C.; Gregori, G.; Schaar, K.; Diziere, A.; Koenig, M.; Pelka, A.; Wang, S.; Dong, Q.; Li, Y.; Takabe, H.

    2013-11-01

    The experiments to simulate astrophysical jet generation are performed using Gekko XII (GXII) HIPER laser system at the Institute of Laser Engineering. In the experiments a fast plasma flow generated by shooting a CH plane (10 μm thickness) is observed at the rear side of the plane. By separating the focal spot of the main beams, a non-uniform plasma is generated. The non-uniform plasma flow in an external magnetic field (0.2˜0.3 T) perpendicular to the plasma is more collimated than that without the external magnetic field. The plasma β, the ratio between the plasma and magnetic pressure, is ≫ 1, and the magnetic Reynolds number is ˜150 in the collimated plasma. It is considered that the magnetic field is distorted by the plasma flow and enhances the jet collimation.

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

    Science.gov (United States)

    Harvey-Thompson, A. J.; Sefkow, A. B.; Nagayama, T. N.; Wei, M. S.; Campbell, E. M.; Fiksel, G.; Chang, P.-Y.; Davies, J. R.; Barnak, D. H.; Glebov, V. Y.; Fitzsimmons, P.; Fooks, J.; Blue, B. E.

    2015-12-01

    We present a platform on the OMEGA EP Laser Facility that creates and diagnoses the conditions present during the preheat stage of the MAGnetized Liner Inertial Fusion (MagLIF) concept. Experiments were conducted using 9 kJ of 3ω (355 nm) light to heat an underdense deuterium gas (electron density: 2.5 ×1020 cm-3=0.025 of critical density) magnetized with a 10 T axial field. Results show that the deuterium plasma reached a peak electron temperature of 670 ± 140 eV, diagnosed using streaked spectroscopy of an argon dopant. The results demonstrate that plasmas relevant to the preheat stage of MagLIF can be produced at multiple laser facilities, thereby enabling more rapid progress in understanding magnetized preheat. Results are compared with magneto-radiation-hydrodynamics simulations, and plans for future experiments are described.

  2. Bondi-Hoyle Accretion in an Isothermal Magnetized Plasma

    CERN Document Server

    Lee, Aaron T; McKee, Christopher F; Klein, Richard I

    2014-01-01

    In regions of star formation, protostars and newborn stars accrete mass from their natal clouds. These clouds are threaded by magnetic fields with a strength characterized by the plasma beta---the ratio of thermal and magnetic pressures. Observations show molecular clouds have beta <= 1, so magnetic fields can play a significant role in the accretion process. We have carried out a numerical study of the effect of large-scale magnetic fields on the rate of accretion onto a uniformly moving point particle from a uniform, non-self-gravitating, isothermal gas. We consider gas moving with sonic Mach numbers of up M ~ 45, magnetic fields that are either parallel, perpendicular, or oriented 45 degrees to the flow, and beta as low as 0.01. Our simulations utilize AMR to obtain high spatial resolution where needed; this also allows the simulation boundaries to be far from the accreting object. Additionally, we show our results are independent of our exact prescription for accreting mass in the sink particle. We giv...

  3. First Measurement of the Magnetic Turbulence Induced Reynolds Stress in a Tokamak

    Institute of Scientific and Technical Information of China (English)

    徐国盛; 万宝年; 宋梅

    2003-01-01

    Reynolds stress component due to magnetic turbulence was first measured in the plasma edge region of the HT- 7 superconducting tokamak using an insertable magnetic probe. A radial gradient of magnetic Reynolds stress was observed to be dose to the velocity shear layer location; however, in this experiment its contribution to driving the poloidal flows is small compared to the electrostatic component. The electron heat transport driven by magnetic turbulence is quite small and cannot account for the total energy transport at the plasma edge.

  4. Intermittent transport in edge plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, O.E.; Naulin, V.; Nielsen, A.H.; Juul Rasmussen, J. [Association EURATOM-Riso National Laboratory, Optics and Plasma Research, Roskilde (Denmark)

    2004-07-01

    The properties of low-frequency convective fluctuations and transport are investigated for the boundary region of magnetized plasmas. We employ a two-dimensional fluid model for the evolution of the global plasma quantities in a geometry and with parameters relevant to the scrape-off layer of confined toroidal plasmas. Strongly intermittent plasma transport is regulated by self-consistently generated sheared poloidal flows and is mediated by burst ejection of particles and heat from the bulk plasma in the form of blobs. Coarse grained probe signals reveal a highly skewed and flat distribution on short time scales, but tends towards a normal distribution at large time scales. Conditionally averaged signals are in perfect agreement with experimental measurements. (authors)

  5. Magnetic helicity balance in the Sustained Spheromak Plasma Experiment

    Science.gov (United States)

    Stallard, B. W.; Hooper, E. B.; Woodruff, S.; Bulmer, R. H.; Hill, D. N.; McLean, H. S.; Wood, R. D.

    2003-07-01

    The magnetic helicity balance between the helicity input injected by a magnetized coaxial gun, the rate-of-change in plasma helicity content, and helicity dissipation in electrode sheaths and Ohmic losses have been examined in the Sustained Spheromak Plasma Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, and R. H. Bulmer, Nucl. Fusion 39, 863 (1999)]. Helicity is treated as a flux function in the mean-field approximation, allowing separation of helicity drive and losses between closed and open field volumes. For nearly sustained spheromak plasmas with low fluctuations, helicity balance analysis implies a decreasing transport of helicity from the gun input into the spheromak core at higher spheromak electron temperature. Long pulse discharges with continuously increasing helicity and larger fluctuations show higher helicity coupling from the edge to the spheromak core. The magnitude of the sheath voltage drop, inferred from cathode heating and a current threshold dependence of the gun voltage, shows that sheath losses are important and reduce the helicity injection efficiency in SSPX.

  6. Experimental studies of axial magnetic fields generated in ultrashort-pulse laser-plasma interaction

    Institute of Scientific and Technical Information of China (English)

    李玉同; 张杰; 陈黎明; 赵理曾; 夏江帆; 魏志义; 江文勉

    2000-01-01

    The quasistatic axial magnetic fields in plasmas produced by ultrashort laser pulses were measured by measuring the Faraday rotation angle of the backscattered emission. The spatial distribution of the axial magnetic field was obtained with a peak value as high as 170 Tesla. Theory suggests that the axial magnetic field is generated by dynamo effect in laser-plasma interaction.

  7. Distributed chaos and solitons at the edges of magnetically confined plasmas

    CERN Document Server

    Bershadskii, A

    2016-01-01

    It is shown, using results of measurements of ion saturation current in the plasma edges of different magnetic fusion confinement devices (tokamaks and stellarators), that the plasma dynamics in the edges is dominated by distributed chaos with spontaneously broken translational symmetry at low magnetic field, and with spontaneously broken reflexional symmetry (by helical solitons) at high magnetic field.

  8. The field line map approach for simulations of magnetically confined plasmas

    CERN Document Server

    Stegmeir, Andreas; Maj, Omar; Hallatschek, Klaus; Lackner, Karl

    2015-01-01

    In the presented field line map approach the simulation domain of a tokamak is covered with a cylindrical grid, which is Cartesian within poloidal planes. Standard finite-difference methods can be used for the discretisation of perpendicular (w.r.t.~magnetic field lines) operators. The characteristic flute mode property $\\left(k_{\\parallel}\\ll k_{\\perp}\\right)$ of structures is exploited computationally by a grid sparsification in the toroidal direction. A field line following discretisation of parallel operators is then required, which is achieved via a finite difference along magnetic field lines. This includes field line tracing and interpolation or integration. The main emphasis of this paper is on the discretisation of the parallel diffusion operator. Based on the support operator method a scheme is constructed which exhibits only very low numerical perpendicular diffusion. The schemes are implemented in the new code GRILLIX, and extensive benchmarks are presented which show the validity of the approach ...

  9. Plasma Beta Dependence of Magnetic Compressibility in Solar Wind Turbulence

    Science.gov (United States)

    Chapman, S. C.; Hnat, B.; Kiyani, K. H.; Sahraoui, F.

    2014-12-01

    The turbulent signature of MHD scales in the near-Earth solar wind are known to be primarily incompressible which manifests itself in magnetic field fluctuation vector components to be aligned primarily perpendicular to the background magnetic field -- so-called "Variance Anisotropy". This, and other facts, have been seen as evidence for a majority Alfvenic turbulence cascade; with a small component (10%) of compressible fluctuations. When one approaches scales on the order of the ion-inertial length and the Larmor radius, this behaviour changes and it is now becoming increasingly evident that the spectral break at these scales is also accompanied by an increase in magnetic compressibility. This has been attributed to a phase change in the physics at these scales -- from fluid to kinetic -- and in particular to the dominant role of the Hall-effect at sub-ion scales. We will be presenting results from the Cluster mission to show how this increase in the compressibility is dependent on the ion plasma beta and what implications this has for the physics at sub-ion scales in the context of prominent theories and models for kinetic plasma turbulence.

  10. Typical Profiles and Distributions of Plasma and Magnetic Field Parameters in Magnetic Clouds at 1 AU

    Science.gov (United States)

    Rodriguez, L.; Masías-Meza, J. J.; Dasso, S.; Démoulin, P.; Zhukov, A. N.; Gulisano, A. M.; Mierla, M.; Kilpua, E.; West, M.; Lacatus, D.; Paraschiv, A.; Janvier, M.

    2016-08-01

    Magnetic clouds (MCs) are a subset of interplanetary coronal mass ejections (ICMEs). They are important because of their simple internal magnetic field configuration, which resembles a magnetic flux rope, and because they represent one of the most geoeffective types of solar transients. In this study, we analyze their internal structure using a superposed epoch method on 63 events observed at L1 by the Advance Composition Explorer (ACE), between 1998 and 2006. In this way, we obtain an average profile for each plasma and magnetic field parameter at each point of the cloud. Furthermore, we take a fixed time-window upstream and downstream from the MC to also sample the regions preceding the cloud and the wake trailing it. We then perform a detailed analysis of the internal characteristics of the clouds and their surrounding solar wind environments. We find that the parameters studied are compatible with log-normal distribution functions. The plasma β and the level of fluctuations in the magnetic field vector are the best parameters to define the boundaries of MCs. We find that one third of the events shows a peak in plasma density close to the trailing edge of the flux ropes. We provide several possible explanations for this result and investigate if the density peak is of a solar origin ( e.g. erupting prominence material) or formed during the magnetic cloud travel from the Sun to 1 AU. The most plausible explanation is the compression due to a fast overtaking flow, coming from a coronal hole located to the east of the solar source region of the magnetic cloud.

  11. Modeling of plasma transport and negative ion extraction in a magnetized radio-frequency plasma source

    Science.gov (United States)

    Fubiani, G.; Garrigues, L.; Hagelaar, G.; Kohen, N.; Boeuf, J. P.

    2017-01-01

    Negative ion sources for fusion are high densities plasma sources in large discharge volumes. There are many challenges in the modeling of these sources, due to numerical constraints associated with the high plasma density, to the coupling between plasma and neutral transport and chemistry, the presence of a magnetic filter, and the extraction of negative ions. In this paper we present recent results concerning these different aspects. Emphasis is put on the modeling approach and on the methods and approximations. The models are not fully predictive and not complete as would be engineering codes but they are used to identify the basic principles and to better understand the physics of the negative ion sources.

  12. Use of a probing pulsed magnetic field for determining plasma parameters

    Science.gov (United States)

    Rousskikh, A. G.; Oreshkin, V. I.; Zhigalin, A. S.; Yushkov, G. Yu.

    2016-11-01

    A novel, simple, and readily usable method is proposed for measuring the electrical conductivity and temperature of a plasma. The method is based on the interaction of the test plasma with a pulsed magnetic field. The electric signals induced by the magnetic field in the circuits of two probes (miniature solenoids), one immersed in the test plasma and the other placed outside the plasma, provide data for estimating the plasma parameters. The method was verified experimentally by determining the parameters of the plasma flows generated in the cathode spots high-current pulsed vacuum arcs that were used to form cylindrical shells of bismuth Z-pinch plasma.

  13. Quark-gluon plasma in strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Kalaydzhyan, Tigran

    2013-04-15

    One of the fundamental problems in subatomic physics is the determination of properties of matter at extreme temperatures, densities and electromagnetic fields. The modern ultrarelativistic heavy-ion experiments are able to study such states (the quark-gluon plasma) and indicate that the physics at extreme conditions differs drastically from what is known from the conventional observations. Also the theoretical methods developed mostly within the perturbative framework face various conceptual problems and need to be replaced by a nonperturbative approach. In this thesis we study the physics of the strongly-coupled quark-gluon plasma in external magnetic fields as well as general electromagnetic and topological properties of the QCD and QCD-like systems. We develop and apply various nonperturbative techniques, based on e.g. gauge-gravity correspondence, lattice QCD simulations, relativistic hydrodynamics and condensed-matter-inspired models.

  14. Energy transfer and dual cascade in kinetic magnetized plasma turbulence.

    Science.gov (United States)

    Plunk, G G; Tatsuno, T

    2011-04-22

    The question of how nonlinear interactions redistribute the energy of fluctuations across available degrees of freedom is of fundamental importance in the study of turbulence and transport in magnetized weakly collisional plasmas, ranging from space settings to fusion devices. In this Letter, we present a theory for the dual cascade found in such plasmas, which predicts a range of new behavior that distinguishes this cascade from that of neutral fluid turbulence. These phenomena are explained in terms of the constrained nature of spectral transfer in nonlinear gyrokinetics. Accompanying this theory are the first observations of these phenomena, obtained via direct numerical simulations using the gyrokinetic code AstroGK. The basic mechanisms that are found provide a framework for understanding the turbulent energy transfer that couples scales both locally and nonlocally.

  15. Accumulative coupling between magnetized tenuous plasma and gravitational waves

    Science.gov (United States)

    Zhang, Fan

    2016-07-01

    We explicitly compute the plasma wave (PW) induced by a plane gravitational wave (GW) traveling through a region of strongly magnetized plasma, governed by force-free electrodynamics. The PW comoves with the GW and absorbs its energy to grow over time, creating an essentially force-free counterpart to the inverse-Gertsenshtein effect. The time-averaged Poynting flux of the induced PW is comparable to the vacuum case, but the associated current may offer a more sensitive alternative to photodetection when designing experiments for detecting/constraining high-frequency gravitational waves. Aside from the exact solutions, we also offer an analysis of the general properties of the GW to PW conversion process, which should find use when evaluating electromagnetic counterparts to astrophysical gravitational waves that are generated directly by the latter as a second-order phenomenon.

  16. Accumulative coupling between magnetized tenuous plasma and gravitational waves

    CERN Document Server

    Zhang, Fan

    2016-01-01

    We explicitly compute the plasma wave (PW) induced by a plane gravitational wave (GW) travelling through a region of strongly magnetized plasma, governed by force-free electrodynamics. The PW co-moves with the GW and absorbs its energy to grow over time, creating an essentially force-free counterpart to the inverse-Gertsenshtein effect. The time-averaged Poynting flux of the induced PW is comparable to the vacuum case, but the associated current may offer a more sensitive alternative to photodetection when designing experiments for detecting/constraining high frequency gravitational waves. Aside from the exact solutions, we also offer an analysis of the general properties of the GW to PW conversion process, which should find use when evaluating electromagnetic counterparts to astrophysical gravitational waves, that are generated directly by the latter as a second order phenomenon.

  17. Electromagnetic waves in a magnetized plasma near the critical surface

    Energy Technology Data Exchange (ETDEWEB)

    Timofeev, Aleksandr V [Russian Research Centre ' Kurchatov Institute' , Moscow (Russian Federation)

    2004-06-30

    Electromagnetic waves in a plasma in a magnetic field give rise to enhanced refraction, produce a change in polarization, and cause electromagnetic energy to flow from one wave mode to another when propagating near the critical surface (CS), the one where the electron Langmuir frequency is equal to the wave frequency. A simple unified model of all phenomena taking place near the CS is proposed. These phenomena are due to electromagnetic waves linearly interacting with electron Langmuir oscillations which are localized at the CS in a cold plasma. This interaction manifests itself most strikingly in electron Langmuir oscillation energy escaping directly into a vacuum in the form of electromagnetic radiation. (reviews of topical problems)

  18. Magnetic Reconnection: A Fundamental Process in Space Plasmas

    Science.gov (United States)

    Hesse, Michael

    2010-01-01

    For many years, collisionless magnetic reconnect ion has been recognized as a fundamental process, which facilitates plasma transport and energy release in systems ranging from the astrophysical plasmas to magnetospheres and even laboratory plasma. Beginning with work addressing solar dynamics, it has been understood that reconnection is essential to explain solar eruptions, the interaction of the solar wind with the magnetosphere, and the dynamics of the magnetosphere. Accordingly, the process of magnetic reconnection has been and remains a prime target for space-based and laboratory studies, as well as for theoretical research. Much progress has been made throughout the years, beginning with indirect verifications by studies of processes enabled by reconnection, such as Coronal Mass Ejections, Flux Transfer Events, and Plasmoids. Theoretical advances have accompanied these observations, moving knowledge beyond the Sweet-Parker theory to the recognition that other, collisionless, effects are available and likely to support much faster reconnect ion rates. At the present time we are therefore near a break-through in our understanding of how collisionless reconnect ion works. Theory and modeling have advanced to the point that two competing theories are considered leading candidates for explaining the microphysics of this process. Both theories predict very small spatial and temporal scales. which are. to date, inaccessible to space-based or laboratory measurements. The need to understand magnetic reconnect ion has led NASA to begin the implementation of a tailored mission, Magnetospheric MultiScale (MMS), a four spacecraft cluster equipped to resolve all relevant spatial and temporal scales. In this presentation, we present an overview of current knowledge as well as an outlook towards measurements provided by MMS.

  19. Cause of sudden magnetic reconnection in a laboratory plasma.

    Science.gov (United States)

    Choi, S; Craig, D; Ebrahimi, F; Prager, S C

    2006-04-14

    The cause for sudden reconnection in reversed field pinch plasmas is determined experimentally for two cases: large reconnection events (the sawtooth crash) and small reconnection events during improved confinement. We measure the term in the MHD equations which represents the driving (or damping) of edge tearing modes due to the axisymmetric magnetic field. The term is negative for large reconnection events (the modes are stable, implying that reconnection may be driven by nonlinear coupling to other modes) and positive for small reconnection events (modes are unstable, reconnection is spontaneous).

  20. Wave propagation in a moving cold magnetized plasma

    Science.gov (United States)

    Hebenstreit, H.

    1980-03-01

    Polarization relations and dispersion equations are derived for media that are electrically anisotropic in the comoving frame. Three-dimensional calculations for media at rest recover the known dispersion equations, i.e., Astrom's dispersion equation for magnetized cold plasmas and Fresnel's wave normal equation for uniaxial crystals. An analogous four-dimensional calculation yields the generalization to moving media. The dispersion equations so obtained for moving gyrotropic media are then discussed qualitatively for various special media and special directions of wave propagation. Finally, the polarization relations are specialized to media gyrotropic in the comoving frame.

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

    Science.gov (United States)

    2011-10-01

    was supported by Gobierno de España, ESP-2007-62694. Publisher Identifier S XXXX-XXXXXXX-X Simulation of plasma flows in divergent magnetic nozzles...Manuscript received ----- M. Merino and E. Ahedo are with the Universidad Politécnica de Madrid, Spain. Work was supported by Gobierno de España, ESP...tion thereon. Additional support came from the Gobierno de España (Project AYA-2010-16699). The authors thank Pro- fessor Martı́nez-Sánchez for his

  2. Evidence of low-dimensional chaos in magnetized plasma turbulence

    CERN Document Server

    Zivkovic, Tatjana

    2008-01-01

    We analyze probe data obtained from a toroidal magnetized plasma configuration suitable for studies of low-frequency gradient-driven instabilities. These instabilities give rise to field-aligned convection rolls analogous to Rayleigh-Benard cells in neutral fluids, and may theoretically develop similar routes to chaos. When using mean-field dimension analysis, we observe low dimensionality, but this could originate from either low-dimensional chaos, periodicity or quasi-periodicity. Therefore, we apply recurrence plot analysis as well as estimation of the largest Lyapunov exponent. These analyses provide evidence of low-dimensional chaos, in agreement with theoretical predictions.

  3. Magnetic field generation during intense laser channelling in underdense plasma

    Science.gov (United States)

    Smyth, A. G.; Sarri, G.; Vranic, M.; Amano, Y.; Doria, D.; Guillaume, E.; Habara, H.; Heathcote, R.; Hicks, G.; Najmudin, Z.; Nakamura, H.; Norreys, P. A.; Kar, S.; Silva, L. O.; Tanaka, K. A.; Vieira, J.; Borghesi, M.

    2016-06-01

    Channel formation during the propagation of a high-energy (120 J) and long duration (30 ps) laser pulse through an underdense deuterium plasma has been spatially and temporally resolved via means of a proton imaging technique, with intrinsic resolutions of a few μm and a few ps, respectively. Conclusive proof is provided that strong azimuthally symmetric magnetic fields with a strength of around 0.5 MG are created inside the channel, consistent with the generation of a collimated beam of relativistic electrons. The inferred electron beam characteristics may have implications for the cone-free fast-ignition scheme of inertial confinement fusion.

  4. Turbulence and intermittent transport at the boundary of magnetized plasmas

    DEFF Research Database (Denmark)

    Garcia, O.E.; Naulin, V.; Nielsen, A.H.

    2005-01-01

    a forcing region with spatially localized sources of particles and heat outside which losses due to the motion along open magnetic-field lines dominate, corresponding to the edge region and the scrape-off layer, respectively. Turbulent states reveal intermittent eruptions of hot plasma from the edge region......, propagating radially far into the scrape-off layer in the form of field-aligned filaments, or blobs. This results in positively skewed and flattened single-point probability distribution functions of particle density and temperature, reflecting the frequent appearance of large fluctuations. The conditional...

  5. Electrical conductivity tensor of dense plasma in magnetic fields

    CERN Document Server

    Harutyunyan, Arus

    2016-01-01

    Electrical conductivity of finite-temperature plasma in neutron star crusts is studied for applications in magneto-hydrodynamical description of compact stars. We solve the Boltzmann kinetic equation in relaxation time approximation taking into account the anisotropy of transport due to the magnetic field, the effects of dynamical screening in the scattering matrix element and corre- lations among the nuclei. We show that conductivity has a minimum at a non-zero temperature, a low-temperature decrease and a power-law increase with increasing temperature. Selected numerical results are shown for matter composed of carbon, iron, and heavier nuclei present in the outer crusts of neutron star.

  6. Magnetic reconnection rate in space plasmas: a fractal approach.

    Science.gov (United States)

    Materassi, Massimo; Consolini, Giuseppe

    2007-10-26

    Magnetic reconnection is generally discussed via a fluid description. Here, we evaluate the reconnection rate assuming a fractal topology of the reconnection region. The central idea is that the fluid hypothesis may be violated at the scales where reconnection takes place. The reconnection rate, expressed as the Alfvén Mach number of the plasma moving toward the diffusion region, is shown to depend on the fractal dimension and on the sizes of the reconnection or diffusion region. This mechanism is more efficient than prediction of the Sweet-Parker model and even Petschek's model for finite magnetic Reynolds number. A good agreement also with rates given by Hall MHD models is found. A discussion of the fractal assumption on the diffusion region in terms of current microstructures is proposed. The comparison with in-situ satellite observations suggests the reconnection region to be a filamentary domain.

  7. Effects of magnetic islands on bootstrap current in toroidal plasmas

    Science.gov (United States)

    Dong, G.; Lin, Z.

    2017-03-01

    The effects of magnetic islands on electron bootstrap current in toroidal plasmas are studied using gyrokinetic simulations. The magnetic islands cause little changes of the bootstrap current level in the banana regime because of trapped electron effects. In the plateau regime, the bootstrap current is completely suppressed at the island centers due to the destruction of trapped electron orbits by collisions and the flattening of pressure profiles by the islands. In the collisional regime, small but finite bootstrap current can exist inside the islands because of the pressure gradients created by large collisional transport across the islands. Finally, simulation results show that the bootstrap current level increases near the island separatrix due to steeper local density gradients.

  8. Magnetic flux reconstruction methods for shaped tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Tsui, Chi-Wa

    1993-12-01

    The use of a variational method permits the Grad-Shafranov (GS) equation to be solved by reducing the problem of solving the 2D non-linear partial differential equation to the problem of minimizing a function of several variables. This high speed algorithm approximately solves the GS equation given a parameterization of the plasma boundary and the current profile (p` and FF` functions). The author treats the current profile parameters as unknowns. The goal is to reconstruct the internal magnetic flux surfaces of a tokamak plasma and the toroidal current density profile from the external magnetic measurements. This is a classic problem of inverse equilibrium determination. The current profile parameters can be evaluated by several different matching procedures. Matching of magnetic flux and field at the probe locations using the Biot-Savart law and magnetic Green`s function provides a robust method of magnetic reconstruction. The matching of poloidal magnetic field on the plasma surface provides a unique method of identifying the plasma current profile. However, the power of this method is greatly compromised by the experimental errors of the magnetic signals. The Casing Principle provides a very fast way to evaluate the plasma contribution to the magnetic signals. It has the potential of being a fast matching method. The performance of this method is hindered by the accuracy of the poloidal magnetic field computed from the equilibrium solver. A flux reconstruction package has been implemented which integrates a vacuum field solver using a filament model for the plasma, a multi-layer perception neural network as an interface, and the volume integration of plasma current density using Green`s functions as a matching method for the current profile parameters. The flux reconstruction package is applied to compare with the ASEQ and EFIT data. The results are promising.

  9. A Rotation/Magnetism Analogy for the Quark Plasma

    CERN Document Server

    McInnes, Brett

    2016-01-01

    In peripheral heavy ion collisions, the Quark-Gluon Plasma that may be formed often has a large angular momentum per unit energy. This angular momentum may take the form of (local) rotation. In many physical systems, rotation can have effects analogous to those produced by a magnetic field; thus, there is a risk that the effects of local rotation in the QGP might be mistaken for those of the large genuine magnetic fields which are also known to arise in these systems. Here we use the gauge-gravity duality to investigate this, and we find indeed that, with realistic parameter values, local rotation has effects on the QGP (at high values of the baryonic chemical potential) which are not only of the same kind as those produced by magnetic fields, but which can in fact be substantially larger. Furthermore, the combined effect of rotation and magnetism is to change the shape of the main quark matter phase transition line in an interesting way, reducing the magnitude of its curvature; again, local rotation contribu...

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

    Energy Technology Data Exchange (ETDEWEB)

    Velikovich, A. L.; Giuliani, J. L. [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States); Zalesak, S. T. [Berkeley Research Associates, Beltsville, Maryland 20705 (United States)

    2015-04-15

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

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

    Science.gov (United States)

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

    2015-04-01

    The magnetized liner inertial fusion (MagLIF) approach to inertial confinement fusion [Slutz et al., Phys. Plasmas 17, 056303 (2010); Cuneo et al., IEEE Trans. Plasma Sci. 40, 3222 (2012)] involves subsonic/isobaric compression and heating of a deuterium-tritium plasma with frozen-in magnetic flux by a heavy cylindrical liner. The losses of heat and magnetic flux from the plasma to the liner are thereby determined by plasma advection and gradient-driven transport processes, such as thermal conductivity, magnetic field diffusion, and thermomagnetic effects. Theoretical analysis based on obtaining exact self-similar solutions of the classical collisional Braginskii's plasma transport equations in one dimension demonstrates that the heat loss from the hot compressed magnetized plasma to the cold liner is dominated by transverse heat conduction and advection, and the corresponding loss of magnetic flux is dominated by advection and the Nernst effect. For a large electron Hall parameter ( ωeτe≫1 ), the effective diffusion coefficients determining the losses of heat and magnetic flux to the liner wall are both shown to decrease with ωeτe as does the Bohm diffusion coefficient c T /(16 e B ) , which is commonly associated with low collisionality and two-dimensional transport. We demonstrate how this family of exact solutions can be used for verification of codes that model the MagLIF plasma dynamics.

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

    Science.gov (United States)

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

    2016-10-01

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

  13. Ideal MHD beta-limits of poloidally asymmetric equilibria

    Energy Technology Data Exchange (ETDEWEB)

    Todd, A.M.M.; Miller, A.E.; Grimm, R.C.; Okabayashi, M.; Dalhed, H.E. Jr.

    1981-05-01

    The ideal MHD stability of poloidally asymmetric equilibria, which are typical of a tokamak reactor design with a single-null poloidal divertor is examined. As with symmetric equilibria, stability to non-axisymmetric modes improves with increasing triangularity and ellipticity, and with lower edge safety factor. Pressure profiles optimized with respect to ballooning stability are obtained for an asymmetric shape, resulting in ..beta../sub critical/ approx. = 5.7%. The corresponding value for an equivalent symmetric shape is ..beta../sub critical/ approx. = 6.5%.

  14. Toroidal and poloidal momentum transport studies in JET

    DEFF Research Database (Denmark)

    Tala, T.; Andrew, Y.; Crombe, K.

    2007-01-01

    of toroidal velocity using the Weiland model and GLF23 also confirm that the ratio chi(phi)/chi(i) approximate to 0.4 reproduces the core toroidal velocity profiles well and similar accuracy with the ion temperature profiles. Concerning poloidal velocities on JET, the experimental measurements show...... that the carbon poloidal velocity can be an order of magnitude above the neo-classical estimate within the ITB. This significantly affects the calculated radial electric field and therefore, the E x B flow shear used for example in transport simulations. Both the Weiland model and GLF23 reproduce the onset...

  15. Tokamak Plasmas : Observation of floating potential asymmetry in the edge plasma of the SINP tokamak

    Indian Academy of Sciences (India)

    Krishnendu Bhattacharyya; N R Ray

    2000-11-01

    Edge plasma properties in a tokamak is an interesting subject of study from the view point of confinement and stability of tokamak plasma. The edge plasma of SINP-tokamak has been investigated using specially designed Langmuir probes. We have observed a poloidal asymmetry of floating potentials, particularly the top-bottom floating potential differences are quite noticeable, which in turn produces a vertical electric field (v). This v remains throughout the discharge but changes its direction at certain point of time which seems to depend on applied vertical magnetic field v).

  16. MAGNETIC FIELD GRADIENT EFFECTS ON ION FLUX BEHAVIORS IN ECR PLASMA SOURCES

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The available electron cyclotron resonance plasma source has been simulated in two-dimensional configuration space (z, r) and three-dimensional velocity space (Vz, Vr Vθ). The simulation is focused on the magnetic field gradient effects on ion flux behaviors in electron cyclotron resonance plasma sources. The simulation results show that, when the magnetic field gradients increase, electron temperature, plasma density, ionization rate, and ion flux in Zdirection would decrease, while ion energy and plasma potential would increase.

  17. A Laboratory Plasma Experiment for Studying Magnetic Dynamics of Accretion Discs and Jets

    OpenAIRE

    Hsu, S. C.; Bellan, P. M.

    2002-01-01

    This work describes a laboratory plasma experiment and initial results which should give insight into the magnetic dynamics of accretion discs and jets. A high-speed multiple-frame CCD camera reveals images of the formation and helical instability of a collimated plasma, similar to MHD models of disc jets, and also plasma detachment associated with spheromak formation, which may have relevance to disc winds and flares. The plasmas are produced by a planar magnetized coaxial gun. The resulting...

  18. Poloidal Field Control for the HT-7U Super conducting Tokamak

    Institute of Scientific and Technical Information of China (English)

    罗家融; 王华忠; 赵皖平

    2002-01-01

    Controlling the poloidal field (PF) in the HT-7U superconducting tokamak is critical to the realization of the mission of advanced tokamak research. Plasma start-up, plasma position, shape, current control and plasma shape reconstruction have been performed as a part of its design process. The PF coils have been designed to produce a wide range of plasmas. Plasma start-up can be achieved for multiple conditions. Fast controlling coils for plasma position inside the vacuum vessel are used for controlling the plasma vertical position on a short timescale. The PF coils control the plasma current and shape on a slower timescale. VXI (VME bus extensions for Instrumentation) Bus system and DSP (Digital Signal Processor is a basic unit of the feedback control system), the response time of which is about (2~4) ms. The basic unit of this system, the hape-controlling algorithms of a few critical points on plasma boundary and real-time equilibrium fitting (RTEFIT) will be described in this paper.

  19. Strong electromagnetic waves in a magnetized relativistic electron-positron plasma

    Energy Technology Data Exchange (ETDEWEB)

    Yu, M.Y.; Shukla, P.K.; Rao, N.N. (Bochum Univ. (Germany, F.R.). Inst. fuer Theoretische Physik)

    1984-12-01

    It is shown that in a strongly magnetized relativistic electron-positron plasma, strongly localized large amplitude circularly polarized electromagnetic wave pulses exist. The localization is due to relativistic mass variation as well as ponderomotive force effects. Three types of pulses are found analytically: the sharply spiked pulse in a strongly magnetized cold plasma, the smooth pulse in a weak magnetized warm plasma, and the moderately spiked pulse for a weakly magnetized cold plasma. The physical mechanisms giving rise to these pulses are distinct for each case. Possible implications of our investigation to pulsar radiation are discussed.

  20. A Laboratory Plasma Experiment for Studying Magnetic Dynamics of Accretion Discs and Jets

    CERN Document Server

    Hsu, S C

    2002-01-01

    This work describes a laboratory plasma experiment and initial results which should give insight into the magnetic dynamics of accretion discs and jets. A high-speed multiple-frame CCD camera reveals images of the formation and helical instability of a collimated plasma, similar to MHD models of disc jets, and also plasma detachment associated with spheromak formation, which may have relevance to disc winds and flares. The plasmas are produced by a planar magnetized coaxial gun. The resulting magnetic topology is dependent on the details of magnetic helicity injection, namely the force-free state eigenvalue alpha_gun imposed by the coaxial gun.

  1. Magnetic Probe to Study Plasma Jets for Magneto-Inertial Fusion

    Energy Technology Data Exchange (ETDEWEB)

    Martens, Daniel [Los Alamos National Laboratory; Hsu, Scott C. [Los Alamos National Laboratory

    2012-08-16

    A probe has been constructed to measure the magnetic field of a plasma jet generated by a pulsed plasma rail-gun. The probe consists of two sets of three orthogonally-oriented commercial chip inductors to measure the three-dimensional magnetic field vector at two separate positions in order to give information about the magnetic field evolution within the jet. The strength and evolution of the magnetic field is one of many factors important in evaluating the use of supersonic plasma jets for forming imploding spherical plasma liners as a standoff driver for magneto-inertial fusion.

  2. Two-dimensional imaging of edge-localized modes in KSTAR plasmas unperturbed and perturbed by n=1 external magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Yun, G. S.; Lee, W.; Choi, M. J.; Lee, J.; Park, H. K. [Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Domier, C. W.; Luhmann, N. C. Jr. [University of California at Davis, Davis, California 95616 (United States); Tobias, B. [Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Donne, A. J. H. [FOM-Institute for Plasma Physics Rijnhuizen, 3430 BE Nieuwegein (Netherlands); Einhoven University of Technology, 5600 MB Einhoven (Netherlands); Lee, J. H.; Jeon, Y. M.; Yoon, S. W. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Collaboration: KSTAR Team

    2012-05-15

    The temporal evolution of edge-localized modes (ELMs) has been studied using a 2-D electron cyclotron emission imaging system in the KSTAR tokamak. The ELMs are observed to evolve in three distinctive stages: the initial linear growth of multiple filamentary structures having a net poloidal rotation, the interim state of regularly spaced saturated filaments, and the final crash through a short transient phase characterized by abrupt changes in the relative amplitudes and distance among filaments. The crash phase, typically consisted of multiple bursts of a single filament, involves a complex dynamics, poloidal elongation of the bursting filament, development of a fingerlike bulge, and fast localized burst through the finger. Substantial alterations of the ELM dynamics, such as mode number, poloidal rotation, and crash time scale, have been observed under external magnetic perturbations with the toroidal mode number n= 1.

  3. Differentially rotating magnetised neutron stars: production of toroidal magnetic fields

    CERN Document Server

    Thampan, A V

    2004-01-01

    We initiate numerical studies of differentially rotating magnetised (proto) neutron stars by studying - through construction from first principles - the coupling between an assumed differential rotation and an impressed magnetic field. For a perfect incompressible, homogeneous, non-dissipative fluid sphere immersed in an ambient plasma, we solve the (coupled) azimuthal components of the Navier-Stokes equation and the Maxwell induction equation. The assumed time--independent poloidal field lines get dragged by the rotating fluid and produce toroidal magnetic fields. Surface magnetic fields take away energy redistributing the angular momentum to produce rigid rotation along poloidal field lines. Due to absence of viscous dissipation, sustained torsional oscillations are set up within the star. However, the perpetual oscillations of neighbouring `closed' field lines get increasingly out of phase with time, leading to structure build up as in Liu & Shapiro (2004) implying the importance of taking into account...

  4. Magnetic Moment Fields in Dense Relativistic Plasma Interacting with Laser Radiations

    Directory of Open Access Journals (Sweden)

    B.Ghosh1* , S.N.Paul 1 , S.Bannerjee2 and C.Das3

    2013-04-01

    Full Text Available Theory of the generation of magnetic moment field from resonant interaction of three high frequency electromagnetic waves in un-magnetized dense electron plasma is developed including the relativistic change of electron mass. It is shown that the inclusion of relativistic effect enhances the magnetic moment field. For high intensity laser beams this moment field may be of the order of a few mega gauss. Such a high magnetic field can considerably affect the transport of electrons in fusion plasma

  5. Induced Compton Scattering by Relativistic Electrons in Magnetized Astrophysical Plasmas.

    Science.gov (United States)

    Sincell, Mark William

    1994-01-01

    The effects of stimulated scattering on high brightness temperature radiation are studied in two important contexts. In the first case, we assume that the radiation is confined to a collimated beam traversing a relativistically streaming magnetized plasma. When the plasma is cold in the bulk frame, stimulated scattering is only significant if the angle between the photon motion and the plasma velocity is less than gamma^{-1} , where gamma is the bulk Lorentz factor. Under the assumption that the center of the photon beam is parallel to the bulk motion, we calculate the scattering rate as a function of the angular spread of the beam and gamma. Magnetization changes the photon recoil, without which stimulated scattering has no effect. It also introduces a strong dependence on frequency and polarization: if the photon frequency matches the electron cyclotron frequency, the scattering rate of photons polarized perpendicular to the magnetic field can be substantially enhanced relative to Thomson, and if the photon frequency is much less than the cyclotron frequency the scattering is suppressed. Applying these calculations to pulsars, we find that stimulated scattering of the radio beam in the magnetized wind believed to exist outside the light cylinder can substantially alter the spectrum and polarization state of the radio signal. We suggest that the scattering rate is so high in some pulsars that the ability of the radio signal to penetrate the pulsar magnetosphere requires modification of either the conventional model of the magnetosphere or assumptions about the effects of stimulated scattering upon a beam. In the second case, we present a model of the radio emission from synchrotron self-absorbed sources, including the effects of induced Compton scattering by the relativistic electrons in the source. Order of magnitude estimates show that stimulated scattering becomes the dominant absorption process when (kTB/m ec^2)tau_{T }_sp{~}> 0.1. Numerical simulations

  6. Plasma, magnetic, and electromagnetic measurements at nonmagnetic bodies

    Science.gov (United States)

    Russell, C. T.; Luhmann, J. G.

    The need to explore the magnetospheres of the Earth and the giant planets is widely recognized and is an integral part of our planetary exploration program. The equal need to explore the plasma, magnetic, and electromagnetic environments of the nonmagnetic bodies is not so widely appreciated. The previous, albeit incomplete, magnetic and electric field measurements at Venus, Mars, and comets have proven critical to our understanding of their atmospheres and ionospheres in areas ranging from planetary lightning to solar wind scavenging and accretion. In the cases of Venus and Mars, the ionospheres can provide communication paths over the horizon for low-altitude probes and landers, but we know little about their lower boundaries. The expected varying magnetic fields below these planetary ionospheres penetrates the planetary crusts and can be used to sound the electrical conductivity and the thermal profiles of the interiors. However, we have no knowledge of the levels of such fields, let alone their morphology. Finally, we note that the absence of an atmosphere and an ionosphere does not make an object any less interesting for the purposes of electromagnetic exploration. Even weak remanent magnetism such as that found on the Moon during the Apollo program provides insight into the present and past states of planetary interiors. We have very intriguing data from our space probes during times of both close and distant passages of asteroids that suggest they may have coherent magnetization. If true, this observation will put important constraints on how the asteroids formed and have evolved. Our planetary exploration program must exploit its full range of exploration tools if it is to characterize the bodies of the solar system thoroughly. We should especially take advantage of those techniques that are proven and require low mass, low power, and low telemetry rates to undertake.

  7. Disruption avoidance through active magnetic feedback in tokamak plasmas

    Science.gov (United States)

    Paccagnella, Roberto; Zanca, Paolo; Yanovskiy, Vadim; Finotti, Claudio; Manduchi, Gabriele; Piron, Chiara; Carraro, Lorella; Franz, Paolo; RFX Team

    2014-10-01

    Disruptions avoidance and mitigation is a fundamental need for a fusion relevant tokamak. In this paper a new experimental approach for disruption avoidance using active magnetic feedback is presented. This scheme has been implemented and tested on the RFX-mod device operating as a circular tokamak. RFX-mod has a very complete system designed for active mode control that has been proved successful for the stabilization of the Resistive Wall Modes (RWMs). In particular the current driven 2/1 mode, unstable when the edge safety factor, qa, is around (or even less than) 2, has been shown to be fully and robustly stabilized. However, at values of qa (qa > 3), the control of the tearing 2/1 mode has been proved difficult. These results suggested the idea to prevent disruptions by suddenly lowering qa to values around 2 where the tearing 2/1 is converted to a RWM. Contrary to the universally accepted idea that the tokamaks should disrupt at low qa, we demonstrate that in presence of a well designed active control system, tokamak plasmas can be driven to low qa actively stabilized states avoiding plasma disruption with practically no loss of the plasma internal energy.

  8. Soft X-ray measurements in magnetic fusion plasma physics

    Science.gov (United States)

    Botrugno, A.; Gabellieri, L.; Mazon, D.; Pacella, D.; Romano, A.

    2010-11-01

    Soft X-ray diagnostic systems and their successful application in the field of magnetic fusion plasma physics are discussed. Radiation with wavelength in the region of Soft X-Ray (1-30 keV) is largely produced by high temperature plasmas, carrying important information on many processes during a plasma discharge. Soft X-ray diagnostics are largely used in various fusion devices all over the world. These diagnostic systems are able to obtain information on electron temperature, electron density, impurity transport, Magneto Hydro Dynamic instabilities. We will discuss the SXR diagnostic installed on FTU in Frascati (Italy) and on Tore Supra in Cadarache (France), with special emphasis on diagnostic performances. Moreover, we will discuss the two different inversion methods for tomographic reconstruction used in Frascati and in Cadarache, the first one is relied on a guessed topology of iso-emissivity surfaces, the second one on regularization techniques, like minimum Fisher or maximum entropy. Finally, a new and very fast 2D imaging system with energy discrimination and high time resolution will be summarized as an alternative approach of SXR detection system.

  9. Experimental study on electromagnetic interactions between plasmas and a vacuum vessel during disruptions in the Hitachi tokamak HT-2

    Energy Technology Data Exchange (ETDEWEB)

    Abe, Mitsushi; Takeuchi, Kazuhiro; Fukumoto, Hideshi; Shimizu, Masashi; Otsuka, Michio (Hitachi Ltd., Ibaraki (Japan). Energy Research Lab.)

    1990-02-01

    Electromagnetic interactions between plasmas and a vacuum vessel during disruptions are examined experimentally in the Hitachi tokamak HT-2. Eddy currents which flow in the toroidal direction and poloidal coil currents are determined from the measured magnetic data. The currents enable calculation of the electromagnetic force on the vacuum vessel and resistively dissipated magnetic energy. Eddy currents and electromagnetic forces are mainly due to the plasma displacement (shell effect), not decay of the plasma current. Large plasma current quench rate -dI{sub p}/dt is associated with scraping of the plasma by the inner limiter through the rapid plasma radial movement, and the decay rate in circular plasma is twice as large as that in elongated plasma. The magnetic energy dissipation is mainly due to the eddy current of the net toroidal current mode which is induced by large current quench rate. (author).

  10. Experimental Study on Electromagnetic Interactions between Plasmas and a Vacuum Vessel during Disruptions in the Hitachi Tokamak HT-2

    Science.gov (United States)

    Abe, Mitsushi; Takeuchi, Kazuhiro; Fukumoto, Hideshi; Shimizu, Masashi; Otsuka, Michio

    1990-02-01

    Electromagnetic interactions between plasmas and a vacuum vessel during disruptions are examined experimentally in the Hitachi tokamak HT-2. Eddy currents which flow in the toroidal direction and poloidal coil currents are determined from the measured magnetic data. The currents enable calculation of the electromagnetic force on the vacuum vessel and resistively dissipated magnetic energy. Eddy currents and electromagnetic forces are mainly due to the plasma displacement (shell effect), not decay of the plasma current. Large plasma current quench rate -dIP/dt is associated with scraping of the plasma by the inner limiter through the rapid plasma radial movement, and the decay rate in circular plasma is twice as large as that in elongated plasma. The magnetic energy dissipation is mainly due to the eddy current of the net toroidal current mode which is induced by large current quench rate.

  11. Disruption forces on the tokamak wall with and without poloidal currents

    Science.gov (United States)

    Pustovitov, V. D.

    2017-05-01

    The contributions into the disruption radial force on the tokamak vacuum vessel wall are calculated and analyzed. One is due to the induced toroidal current in the wall, and another is due to the poloidal current. The latter is not accounted for in the models that represent the wall as a set of isolated toroidal filaments. It is shown that such modeling must lead to significant errors in the evaluation of the force during either thermal or current quench. The analytical derivations are performed here for an arbitrary tokamak configuration with final estimates for a circular large-aspect-ratio plasma and a coaxial wall reacting on perturbations as a perfect conductor. The results are compared with those recently obtained numerically by the codes DINA, MAXFEA and CarMa0NL. The discrepancies between the DINA simulations (Khayrutdinov et al 2016 Plasma Phys. Control. Fusion 58 115012) and earlier analytical predictions are explained. The recent conclusion (Villone et al 2015 Fusion Eng. Des. 93 57) on the role of the disruption-induced poloidal current in the wall is confirmed and extended to a wider area.

  12. Role of external magnetic field and current closure in the force balance mechanism of a magnetically stabilized plasma torch

    Science.gov (United States)

    G, Ravi; Goyal, Vidhi

    2012-10-01

    Experimental investigations on the role of applied external magnetic field and return current closure in the force balance mechanism of a plasma torch are reported. The plasma torch is of low power and has wall, gas and magnetic stabilization mechanisms incorporated in it. Gas flow is divided into two parts: axial-central and peripheral-shroud, applied magnetic field is axial and return current is co-axial. Results indicate that application of large external magnetic field gives rise to not only J x B force but also, coupled with gas flow, to a new drag-cum-centrifugal force that acts on the plasma arc root and column. The magnetic field also plays a role in the return current closure dynamics and thus in the overall force balance mechanism. This in turn affects the electro-thermal efficiency of the plasma torch. Detailed experimental results, analytical calculations and physical model representing the processes will be presented and discussed.

  13. Experimental identification of an azimuthal current in a magnetic nozzle of a radiofrequency plasma thruster

    Science.gov (United States)

    Takahashi, Kazunori; Chiba, Aiki; Komuro, Atsushi; Ando, Akira

    2016-10-01

    The azimuthal plasma current in a magnetic nozzle of a radiofrequency plasma thruster is experimentally identified by measuring the plasma-induced magnetic field. The axial plasma momentum increases over about 20 cm downstream of the thruster exit due to the Lorentz force arising from the azimuthal current. The measured current shows that the azimuthal current is given by the sum of the electron diamagnetic drift and \\mathbf{E}× \\mathbf{B} drift currents, where the latter component decreases with an increase in the magnetic field strength; hence the azimuthal current approaches the electron diamagnetic drift one for the strong magnetic field. The Lorentz force calculated from the measured azimuthal plasma current and the radial magnetic field is smaller than the directly measured force exerted to the magnetic field, which indicates the existence of a non-negligible Lorentz force in the source tube.

  14. Behavior of moving plasma in solenoidal magnetic field in a laser ion source

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, S., E-mail: ikeda.s.ae@m.titech.ac.jp [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8502 (Japan); Nishina Center for Accelerator-Based Science, RIKEN, Wako, Saitama 351-0108 (Japan); Takahashi, K. [Department of Electrical Engineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2137 (Japan); Okamura, M. [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Horioka, K. [Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8502 (Japan)

    2016-02-15

    In a laser ion source, a solenoidal magnetic field is useful to guide the plasma and to control the extracted beam current. However, the behavior of the plasma drifting in the magnetic field has not been well understood. Therefore, to investigate the behavior, we measured the plasma ion current and the total charge within a single pulse in the solenoid by changing the distance from the entrance of the solenoid to a detector. We observed that the decrease of the total charge along the distance became smaller as the magnetic field became larger and then the charge became almost constant with a certain magnetic flux density. The results indicate that the transverse spreading speed of the plasma decreased with increasing the field and the plasma was confined transversely with the magnetic flux density. We found that the reason of the confinement was not magnetization of ions but an influence induced by electrons.

  15. Behavior of moving plasma in solenoidal magnetic field in a laser ion source

    Science.gov (United States)

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

    2016-02-01

    In a laser ion source, a solenoidal magnetic field is useful to guide the plasma and to control the extracted beam current. However, the behavior of the plasma drifting in the magnetic field has not been well understood. Therefore, to investigate the behavior, we measured the plasma ion current and the total charge within a single pulse in the solenoid by changing the distance from the entrance of the solenoid to a detector. We observed that the decrease of the total charge along the distance became smaller as the magnetic field became larger and then the charge became almost constant with a certain magnetic flux density. The results indicate that the transverse spreading speed of the plasma decreased with increasing the field and the plasma was confined transversely with the magnetic flux density. We found that the reason of the confinement was not magnetization of ions but an influence induced by electrons.

  16. Theory of the Jitter radiation in a magnetized plasma accompanying temperature gradient

    CERN Document Server

    Hattori, Makoto

    2016-01-01

    The linear stability of a magnetized plasma accompanying temperature gradient was reexamined by using plasma kinetic theory. The anisotropic velocity distribution function was decomposed into two components. One is proportional to the temperature gradient parallel to and the other is proportional to the temperature gradient perpendicular to the back ground magnetic field. Since the amplitude of the anisotropic velocity distribution function is proportional to the heat conductivity and the heat conductivities perpendicular to the magnetic field is strongly reduced, the first component of the anisotropic velocity distribution function is predominant. The anisotropic velocity distribution function induced by the temperature gradient along the back ground magnetic field drives plasma kinetic instability and the circular polarized magnetic plasma waves are excited. The instability is almost identical to Weibel instability in weakly magnetized plasma. However, depending on whether wave vectors of modes are parallel...

  17. Effect of radial plasma transport at the magnetic throat on axial ion beam formation

    Science.gov (United States)

    Zhang, Yunchao; Charles, Christine; Boswell, Rod

    2016-08-01

    Correlation between radial plasma transport and formation of an axial ion beam has been investigated in a helicon plasma reactor implemented with a convergent-divergent magnetic nozzle. The plasma discharge is sustained under a high magnetic field mode and a low magnetic field mode for which the electron energy probability function, the plasma density, the plasma potential, and the electron temperature are measured at the magnetic throat, and the two field modes show different radial parametric behaviors. Although an axial potential drop occurs in the plasma source for both field modes, an ion beam is only observed in the high field mode while not in the low field mode. The transport of energetic ions is characterized downstream of the plasma source using the delimited ion current and nonlocal ion current. A decay of ion beam strength is also observed in the diffusion chamber.

  18. Transient growth of a Vlasov plasma in a weakly inhomogeneous magnetic field

    KAUST Repository

    Ratushnaya, Valeria

    2016-12-17

    We investigate the stability properties of a collisionless Vlasov plasma in a weakly inhomogeneous magnetic field using non-modal stability analysis. This is an important topic in a physics of tokamak plasma rich in various types of instabilities. We consider a thin tokamak plasma in a Maxwellian equilibrium, subjected to a small arbitrary perturbation. Within the framework of kinetic theory, we demonstrate the emergence of short time scale algebraic instabilities evolving in a stable magnetized plasma. We show that the linearized governing operator (Vlasov operator) is non-normal leading to the transient growth of the perturbations on the time scale of several plasma periods that is subsequently followed by Landau damping. We calculate the first-order distribution function and the electric field and study the dependence of the transient growth characteristics on the magnetic field strength and perturbation parameters of the system. We compare our results with uniformly magnetized plasma and field-free Vlasov plasma.

  19. Transient growth of a Vlasov plasma in a weakly inhomogeneous magnetic field

    Science.gov (United States)

    Ratushnaya, Valeria; Samtaney, Ravi

    2016-12-01

    We investigate the stability properties of a collisionless Vlasov plasma in a weakly inhomogeneous magnetic field using non-modal stability analysis. This is an important topic in a physics of tokamak plasma rich in various types of instabilities. We consider a thin tokamak plasma in a Maxwellian equilibrium, subjected to a small arbitrary perturbation. Within the framework of kinetic theory, we demonstrate the emergence of short time scale algebraic instabilities evolving in a stable magnetized plasma. We show that the linearized governing operator (Vlasov operator) is non-normal leading to the transient growth of the perturbations on the time scale of several plasma periods that is subsequently followed by Landau damping. We calculate the first-order distribution function and the electric field and study the dependence of the transient growth characteristics on the magnetic field strength and perturbation parameters of the system. We compare our results with uniformly magnetized plasma and field-free Vlasov plasma.

  20. Vectorial transport processes in a magnetized and non-magnetized plasma

    CERN Document Server

    García-Colin, L S; Sandoval-Villalbazo, A

    2006-01-01

    It is well known that magnetic fields affect heat conduction in a different way in the direction parallel and perpendicular to the field. In this paper we present a formal derivation of this phenomenon and an analytical expression for the transport coefficients based in the Boltzmann equation. Moreover, the Dufour effect or thermo diffusion is usually ignored in plasma transport theory. This effect is here shown to be not only relevant but also the most important source of heat conduction for weak magnetic fields. In this work we formally derive analytic expressions for the parallel and perpendicular thermal conductivities as well as the coefficients for the thermal diffusion cross-effect. We show how the heat conduction in the perpendicular direction decreases with increasing magnetic fields and how in both directions thermal diffusion is far more important than thermal conduction, leading to a new effective thermal conductiviy coefficient. Other aspects of this work are also emphasized.

  1. Internal Magnetic Field, Temperature and Density Measurements on Magnetized HED plasmas using Pulsed Polarimetry

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Roger J. [Univ. of Washington, Seattle, WA (United States)

    2016-10-20

    The goals were to collaborate with the MSX project and make the MSX platform reliable with a performance where pulsed polarimetry would be capable of adding a useful measurement and then to achieve a first measurement using pulsed polarimetry. The MSX platform (outside of laser blow off plasmas adjacent to magnetic fields which are low beta) is the only device that can generate high beta magnetized collisionless supercritical shocks, and with a large spatial size of ~10 cm. Creating shocks at high Mach numbers and investigating the dynamics of the shocks was the main goal of the project. The MSX shocks scale to astrophysical magnetized shocks and potentially throw light on the generation of highly energetic particles via a mechanism like the Fermi process.

  2. Toroidal and poloidal momentum transport studies in tokamaks

    DEFF Research Database (Denmark)

    Tala, T.; Crombé, K.; Vries, P.C. de

    2007-01-01

    codes and also the Weiland model predict the existence of an anomalous poloidal velocity, peaking in the vicinity of the ITB and driven dominantly by the flow due to the Reynold's stress. It is worth noting that these codes and models treat the equilibrium in a simplified way and this affects...

  3. Degenerate mixing of plasma waves on cold, magnetized single-species plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, M. W.; O' Neil, T. M.; Dubin, D. H. E.; Gould, R. W. [Physics Department, University of California at San Diego, La Jolla, California 92093 (United States)

    2011-10-15

    In the cold-fluid dispersion relation {omega}={omega}{sub p}/[1+(k{sub perpendicular}/k{sub z}){sup 2}]{sup 1/2} for Trivelpiece-Gould waves on an infinitely long magnetized plasma cylinder, the transverse and axial wavenumbers appear only in the combination k{sub perpendicular}/k{sub z}. As a result, for any frequency {omega}<{omega}{sub p}, there are infinitely many degenerate waves, all having the same value of k{sub perpendicular}/k{sub z}. On a cold finite-length plasma column, these degenerate waves reflect into one another at the ends; thus, each standing-wave normal mode of the bounded plasma is a mixture of many degenerate waves, not a single standing wave as is often assumed. A striking feature of the many-wave modes is that the short-wavelength waves often add constructively along resonance cones given by dz/dr={+-}({omega}{sub p}{sup 2}/{omega}{sup 2}-1){sup 1/2}. Also, the presence of short wavelengths in the admixture for a predominantly long-wavelength mode enhances the viscous damping beyond what the single-wave approximation would predict. Here, numerical solutions are obtained for modes of a cylindrical plasma column with rounded ends. Exploiting the fact that the modes of a spheroidal plasma are known analytically (the Dubin modes), a perturbation analysis is used to investigate the mixing of low-order, nearly degenerate Dubin modes caused by small deformations of a plasma spheroid.

  4. Bondi-Hoyle accretion in an isothermal magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Aaron T.; McKee, Christopher F.; Klein, Richard I. [Department of Astronomy, University of California Berkeley, Berkeley, CA 94720 (United States); Cunningham, Andrew J., E-mail: a.t.lee@berkeley.edu [Lawrence Livermore National Laboratory, P.O. Box 808, L-23, Livermore, CA 94550 (United States)

    2014-03-01

    In regions of star formation, protostars and newborn stars will accrete mass from their natal clouds. These clouds are threaded by magnetic fields with a strength characterized by the plasma β—the ratio of thermal and magnetic pressures. Observations show that molecular clouds have β ≲ 1, so magnetic fields have the potential to play a significant role in the accretion process. We have carried out a numerical study of the effect of large-scale magnetic fields on the rate of accretion onto a uniformly moving point particle from a uniform, non-self-gravitating, isothermal gas. We consider gas moving with sonic Mach numbers of up to M≈45; magnetic fields that are either parallel, perpendicular, or oriented 45° to the flow; and β as low as 0.01. Our simulations utilize adaptive mesh refinement in order to obtain high spatial resolution where it is needed; this also allows the boundaries to be far from the accreting object to avoid unphysical effects arising from boundary conditions. Additionally, we show that our results are independent of our exact prescription for accreting mass in the sink particle. We give simple expressions for the steady-state accretion rate as a function of β and M for the parallel and perpendicular orientations. Using typical molecular cloud values of M∼5 and β ∼ 0.04 from the literature, our fits suggest that a 0.4 M {sub ☉} star accretes ∼4 × 10{sup –9} M {sub ☉} yr{sup –1}, almost a factor of two less than accretion rates predicted by hydrodynamic models. This disparity can grow to orders of magnitude for stronger fields and lower Mach numbers. We also discuss the applicability of these accretion rates versus accretion rates expected from gravitational collapse, and under what conditions a steady state is possible. The reduction in the accretion rate in a magnetized medium leads to an increase in the time required to form stars in competitive accretion models, making such models less efficient than predicted by

  5. A novel flexible field-aligned coordinate system for tokamak edge plasma simulation

    CERN Document Server

    Leddy, Jarrod; Romanelli, Michele; Shanahan, Brendan; Walkden, Nick

    2016-01-01

    Tokamak plasmas are confined by a magnetic field that limits the particle and heat transport perpendicular to the field. Parallel to the field the ionised particles can move freely, so to obtain confinement the field lines are "closed" (ie. form closed surfaces of constant poloidal flux) in the core of a tokamak. Towards, the edge, however, the field lines begin to intersect physical surfaces, leading to interaction between neutral and ionised particles, and the potential melting of the material surface. Simulation of this interaction is important for predicting the performance and lifetime of future tokamak devices such as ITER. Field-aligned coordinates are commonly used in the simulation of tokamak plasmas due to the geometry and magnetic topology of the system. However, these coordinates are limited in the geometry they allow in the poloidal plane due to orthogonality requirements. A novel 3D coordinate system is proposed herein that relaxes this constraint so that any arbitrary, smoothly varying geometry...

  6. Evolution of plasma parameters in a He - N2/Ar magnetic pole enhanced inductive plasma source

    Science.gov (United States)

    Younus, Maria; Rehman, N. U.; Shafiq, M.; Zakaullah, M.; Abrar, M.

    2016-02-01

    A magnetic pole enhanced inductively coupled H e - N2/A r plasma is studied at low pressure, to monitor the effects of helium mixing on plasma parameters like electron number density (ne) , electron temperature (Te) , plasma potential (Vp ) , and electron energy probability functions (EEPFs). An RF compensated Langmuir probe is employed to measure these plasma parameters. It is noted that electron number density increases with increasing RF power and helium concentration in the mixture, while it decreases with increase in filling gas pressure. On the other hand, electron temperature shows an increasing trend with helium concentration in the mixture. At low RF powers and low helium concentration in the mixture, EEPFs show a "bi-Maxwellian" distribution with pressure. While at RF powers greater than 50 W and higher helium concentration in the mixture, EEPFs evolve into "Maxwellian" distribution. The variation of skin depth with RF power and helium concentration in the mixture, and its relation with EEPF are also studied. The effect of helium concentrations on the temperatures of two electron groups ( Tb u l k and Tt a i l ) in the "bi-Maxwellian" EEPFs is also observed. The temperature of low energy electron group ( Tb u l k) shows significant increase with helium addition, while the temperature of tail electrons ( Tt a i l) increases smoothly as compared to ( Tb u l k).

  7. Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, Shunsuke, E-mail: shunsuke.ikeda@riken.jp; Sekine, Megumi [Tokyo Institute of Technology, Yokohama, Kanagawa (Japan); Riken, Wako, Saitama (Japan); Romanelli, Mark [Cornell University, Ithaca, New York 14850 (United States); Cinquegrani, David [University of Michigan, Ann Arbor, Michigan 48109 (United States); Kumaki, Masafumi [Waseda University, Shinjuku, Tokyo (Japan); Fuwa, Yasuhiro [Kyoto University, Uji, Kyoto (Japan); Kanesue, Takeshi; Okamura, Masahiro [Brookhaven National Laboratory, Upton, New York 11973 (United States); Horioka, Kazuhiko [Tokyo Institute of Technology, Yokohama, Kanagawa (Japan)

    2014-02-15

    A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

  8. Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

    Science.gov (United States)

    Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

    2014-02-01

    A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

  9. Slowing of Magnetic Reconnection Concurrent with Weakening Plasma Inflows and Increasing Collisionality in Strongly Driven Laser-Plasma Experiments.

    Science.gov (United States)

    Rosenberg, M J; Li, C K; Fox, W; Zylstra, A B; Stoeckl, C; Séguin, F H; Frenje, J A; Petrasso, R D

    2015-05-22

    An evolution of magnetic reconnection behavior, from fast jets to the slowing of reconnection and the establishment of a stable current sheet, has been observed in strongly driven, β≲20 laser-produced plasma experiments. This process has been inferred to occur alongside a slowing of plasma inflows carrying the oppositely directed magnetic fields as well as the evolution of plasma conditions from collisionless to collisional. High-resolution proton radiography has revealed unprecedented detail of the forced interaction of magnetic fields and super-Alfvénic electron jets (V_{jet}∼20V_{A}) ejected from the reconnection region, indicating that two-fluid or collisionless magnetic reconnection occurs early in time. The absence of jets and the persistence of strong, stable magnetic fields at late times indicates that the reconnection process slows down, while plasma flows stagnate and plasma conditions evolve to a cooler, denser, more collisional state. These results demonstrate that powerful initial plasma flows are not sufficient to force a complete reconnection of magnetic fields, even in the strongly driven regime.

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

    Science.gov (United States)

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

    2016-10-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Schlickeiser, R., E-mail: rsch@tp4.rub.de, E-mail: yoonp@umd.edu [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Yoon, P. H., E-mail: rsch@tp4.rub.de, E-mail: yoonp@umd.edu [Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); School of Space Research, Kyung Hee University, Yongin-Si, Gyeonggi-Do 446-701 (Korea, Republic of)

    2015-07-15

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

  12. Magnetic shield for turbomolecular pump of the Magnetized Plasma Linear Experimental device at Saha Institute of Nuclear Physics.

    Science.gov (United States)

    Biswas, Subir; Chattopadhyay, Monobir; Pal, Rabindranath

    2011-01-01

    The turbo molecular pump of the Magnetized Plasma Linear Experimental device is protected from damage by a magnetic shield. As the pump runs continuously in a magnetic field environment during a plasma physics experiment, it may get damaged owing to eddy current effect. For design and testing of the shield, first we simulate in details various aspects of magnetic shield layouts using a readily available field design code. The performance of the shield made from two half cylinders of soft iron material, is experimentally observed to agree very well with the simulation results.

  13. Two-dimensional electric current effects on a magnetized plasma in contact with a surface

    NARCIS (Netherlands)

    Shumack, A. E.; de Blank, H. J.; Westerhout, J.; van Rooij, G. J.

    2012-01-01

    Significant electric fields both parallel and perpendicular to a magnetic field have been observed and modeled self-consistently in an ITER divertor relevant plasma–wall experiment. Due to magnetization, electric current is found to penetrate the plasma beam outside of the cascaded arc plasma source

  14. Generation of magnetic fields by the ponderomotive force of electromagnetic waves in dense plasmas

    OpenAIRE

    Shukla, P K; Shukla, Nitin; Stenflo, Lennart

    2010-01-01

    We show that the non-stationary ponderomotive force of a, large-amplitude electromagnetic move in a very dense quantum plasma wall streaming degenerate electrons can spontaneously create d.c. magnetic fields. The present result can account for the seed magnetic fields in compact astrophysical objects and in the next-generation intense laser-solid density, plasma interaction experiments.

  15. Feedback Control of Plasma Current and Horizontal Position in HT-7

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    There is a strong magnetic coupling between poloidal field coils of superconducting tokamak HT-7, especially between ohinic heating and vertical field coils. These coils are connected to individual power supply. The control system for the plasma current and horizontal position control has been designed and showed satisfactory results with the feedback control of multivariable feedforward-decoupling and var-parameter PID controller to simultaneously modulate power supplies. The design and analysis of the control system is presented.

  16. MMS observations of ion-scale magnetic island in the magnetosheath turbulent plasma

    Science.gov (United States)

    Huang, S. Y.; Sahraoui, F.; Retino, A.; Le Contel, O.; Yuan, Z. G.; Chasapis, A.; Aunai, N.; Breuillard, H.; Deng, X. H.; Zhou, M.; Fu, H. S.; Pang, Y.; Wang, D. D.; Torbert, R. B.; Goodrich, K. A.; Ergun, R. E.; Khotyaintsev, Y. V.; Lindqvist, P.-A.; Russell, C. T.; Strangeway, R. J.; Magnes, W.; Bromund, K.; Leinweber, H.; Plaschke, F.; Anderson, B. J.; Pollock, C. J.; Giles, B. L.; Moore, T. E.; Burch, J. L.

    2016-08-01

    In this letter, first observations of ion-scale magnetic island from the Magnetospheric Multiscale mission in the magnetosheath turbulent plasma are presented. The magnetic island is characterized by bipolar variation of magnetic fields with magnetic field compression, strong core field, density depletion, and strong currents dominated by the parallel component to the local magnetic field. The estimated size of magnetic island is about 8 di, where di is the ion inertial length. Distinct particle behaviors and wave activities inside and at the edges of the magnetic island are observed: parallel electron beam accompanied with electrostatic solitary waves and strong electromagnetic lower hybrid drift waves inside the magnetic island and bidirectional electron beams, whistler waves, weak electromagnetic lower hybrid drift waves, and strong broadband electrostatic noise at the edges of the magnetic island. Our observations demonstrate that highly dynamical, strong wave activities and electron-scale physics occur within ion-scale magnetic islands in the magnetosheath turbulent plasma.

  17. Effects of magnetic drift tangential to magnetic surfaces on neoclassical transport in non-axisymmetric plasmas

    CERN Document Server

    Matsuoka, Seikichi; Kanno, Ryutaro; Sugama, Hideo

    2015-01-01

    In evaluating neoclassical transport by radially-local simulations, the magnetic drift tangential to a flux surface is usually ignored in order to keep the phase-space volume conservation. In this paper, effect of the tangential magnetic drift on the local neoclassical transport are investigated. To retain the effect of the tangential magnetic drift in the local treatment of neoclassical transport, a new local formulation for the drift kinetic simulation is developed. The compressibility of the phase-space volume caused by the tangential magnetic drift is regarded as a source term for the drift kinetic equation, which is solved by using a two-weight $\\delta f$ Monte Carlo method for non-Hamiltonian system [G. Hu and J. A. Krommes, Phys. Plasmas $\\rm \\textbf{1}$, 863 (1994)]. It is demonstrated that the effect of the drift is negligible for the neoclassical transport in tokamaks. In non-axisymmetric systems, however, the tangential magnetic drift substantially changes the dependence of the neoclassical transpo...

  18. Cosmic electrodynamics electrodynamics and magnetic hydrodynamics of cosmic plasmas

    CERN Document Server

    Fleishman, Gregory D

    2013-01-01

    This volume offers a deep and detailed overview of plasma behavior in diverse astrophysical conditions. The presentation is based on a solid science foundation that includes well established physical laws of electromagnetism, hydrodynamics, classical and quantum mechanics and other relevant fields of science. Qualitative ideas and descriptions are followed by quantitative derivations and estimates of key physical quantities, and the results of theories and models are confronted with modern observational data obtained from numerous international science programs. Fundamental astrophysical phenomena, such as charged particle acceleration and magnetic field generation, are presented along with spectacular phenomena, such as stellar winds (including ultra-relativistic pulsar wind), supernova explosions and evolution of its remnants, and solar flares.

  19. Weibel instability in a plasma with nonzero external magnetic field

    Directory of Open Access Journals (Sweden)

    O. A. Pokhotelov

    2012-07-01

    Full Text Available The theory of the Weibel instability is generalized for the case of a plasma immersed in a nonzero external magnetic field. It is shown that the presence of this external field modifies the dispersion relation for this mode which now possesses a nonzero frequency. The explicit expression for the real and imaginary parts of the frequency is then calculated. It turns out that the linear growth rate remains unchanged, whereas the frequency becomes nonzero due to the finite value of the electron cyclotron frequency. The frequency of the Weibel mode is found to be proportional to the electron temperature anisotropy. The formal similarity of the Weibel and drift-mirror instabilities is outlined.

  20. Contactless steering of a plasma jet with a 3D magnetic nozzle

    Science.gov (United States)

    Merino, Mario; Ahedo, Eduardo

    2017-09-01

    A 3D, steerable magnetic nozzle (MN) is presented that enables contactless thrust vector control of a plasma jet without any moving parts. The concept represents a substantial simplification over current plasma thruster gimbaled platforms, and requires only a small modification in thrusters that already have a MN. The characteristics of the plasma expansion in the 3D magnetic field and the deflection performance of the device are characterized with a fully magnetized plasma model, suggesting that thrust deflections of 5° -10° are readily achievable.

  1. Plasma response based RMP coil geometry optimization for an ITER plasma

    Science.gov (United States)

    Zhou, Lina; Liu, Yueqiang; Liu, Yue; Yang, Xu

    2016-11-01

    Based on an ITER 15MA Q  =  10 inductive scenario, a systematic numerical investigation is carried out in order to understand the effect of varying the geometry of the magnetic coils, used for controlling the edge localized modes in tokamaks, on the plasma response to the resonant magnetic perturbation (RMP) fields produced by these coils. Toroidal computations show that both of the plasma response based figures of merit—one is the pitch resonant radial field component near the plasma edge and the other is the plasma displacement near the X-point of the separatrix—consistently yield the same prediction for the optimal coil geometry. With a couple of exceptions, the presently designed poloidal location of the ITER upper and lower rows of RMP coils is close to the optimum, according to the plasma response based criteria. This holds for different coil current configurations with n  =  2, 3, 4, as well as different coil phasing between the upper and lower rows. The coils poloidal width from the present design, on the other hand, is sub-optimal for the upper and lower rows. Modelling also finds that the plasma response amplitude sharply decreases by moving the middle row RMP coils of ITER from the designed radial location (just inside the inner vacuum vessel) outwards (outside the outer vacuum vessel). The decay rate is sensitively affected by the middle row coils’ poloidal coverage for low-n (n  =  1, 2) RMP fields, but not for high-n (n  =  4) fields.

  2. Numerical evaluation of external magnetic effect on electromagnetic wave transmission through reentry plasma layer

    Science.gov (United States)

    Zhao, Qing; Bo, Yong; Lei, Mingda; Liu, Shuzhang; Liu, Ying; Liu, Jianwei; Zhao, Yizhe

    2016-11-01

    Numerical study of electromagnetic (EM) wave transmission through the magnetized plasma layer is presented in this paper. The plasma parameters are derived from computational fluid dynamics simulation of the flow field around a blunt body flying at supersonic speed and serve as the background plasma condition in the numerical modeling for EM wave transmission. The EM wave is generated by our newly designed coaxial feed GPS patch antenna. The external magnetic field is applied and assumed to vary linearly as a function of wall distance. The effects of the external applied magnetic field and the plasma parameters on wave transmission are studied, and the results show that EM wave propagation in the non-uniformly magnetized plasma is a matter of impedance matching, and the EM wave transmission can be adjusted only when the proper strength of the magnetic field is applied.

  3. The impact of magnetic geometry on wave modes in cylindrical plasmas

    CERN Document Server

    Chang, Lei

    2015-01-01

    Both space and laboratory plasmas can be associated with static magnetic field, and the field geometry varies from uniform to non-uniform. This thesis investigates the impact of magnetic geometry on wave modes in cylindrical plasmas. The cylindrical configuration is chosen so as to explore this impact in a tractable but experimentally realisable configuration. Three magnetic geometries are considered: uniform, focused and rippled. These studies suggest suppressing drift waves in a uniformly magnetised plasma by increasing the field strength, enhancing the efficiency of helicon wave production of plasma by using a focused magnetic field, and forming a gap eigenmode on a linear plasma device by introducing a local defect to the system's periodicity, which is useful for understanding the gap-mode formation and interaction with energetic particles in fusion plasmas.

  4. Influence of external magnetic field on laser breakdown plasma in aqueous Au nanoparticles colloidal solutions

    CERN Document Server

    Serkov, A A; Simakin, A V; Kuzmin, P G; Mikhailova, G N; Antonova, L Kh; Troitskii, A V; Kuzmin, G P; Shafeev, G A

    2016-01-01

    Influence of permanent magnetic field up to 7.5 T on plasma emission and laser-assisted Au nanoparticles fragmentation in water is experimentally studied. It is found that presence of magnetic field causes the breakdown plasma emission to start earlier regarding to laser pulse. Field presence also accelerates the fragmentation of nanoparticles down to a few nanometers. Dependence of Au NPs fragmentation rate in water on magnetic field intensity is investigated. The results are discussed on the basis of laser-induced plasma interaction with magnetic field.

  5. Comment on "Propagation of surface waves on a semi-bounded quantum magnetized collisional plasma" [Phys. Plasmas 20, 122106 (2013)

    Science.gov (United States)

    Moradi, Afshin

    2016-04-01

    In a recent article [Niknam et al., Phys. Plasmas 20, 122106 (2013)], Niknam et al. investigated the propagation of TM surface waves on a semi-bounded quantum magnetized collisional plasma in the Faraday configuration (in this case, the magnetic field is parallel to the both of the plasma surface and direction of propagation). Here, we present a fresh look at the problem and show that TM surface waves cannot propagate on surface of the present system. We find in the Faraday configuration the surface waves acquire both TM and TE components due to the cyclotron motion of electrons. Therefore, the main result of the work by Niknam et al. is incorrect.

  6. Relation between magnetic fields and electric currents in plasmas

    Directory of Open Access Journals (Sweden)

    V. M. Vasyliunas

    2005-10-01

    Full Text Available Maxwell's equations allow the magnetic field B to be calculated if the electric current density J is assumed to be completely known as a function of space and time. The charged particles that constitute the current, however, are subject to Newton's laws as well, and J can be changed by forces acting on charged particles. Particularly in plasmas, where the concentration of charged particles is high, the effect of the electromagnetic field calculated from a given J on J itself cannot be ignored. Whereas in ordinary laboratory physics one is accustomed to take J as primary and B as derived from J, it is often asserted that in plasmas B should be viewed as primary and J as derived from B simply as (c/4π∇×B. Here I investigate the relation between ∇×B and J in the same terms and by the same method as previously applied to the MHD relation between the electric field and the plasma bulk flow vmv2001: assume that one but not the other is present initially, and calculate what happens. The result is that, for configurations with spatial scales much larger than the electron inertial length λe, a given ∇×B produces the corresponding J, while a given J does not produce any ∇×B but disappears instead. The reason for this can be understood by noting that ∇×B≠4π/cJ implies a time-varying electric field (displacement current which acts to change both terms (in order to bring them toward equality; the changes in the two terms, however, proceed on different time scales, light travel time for B and electron plasma period for J, and clearly the term changing much more slowly is the one that survives. (By definition, the two time scales are equal at λe. On larger scales, the evolution of B (and hence also of ∇×B is governed by

  7. Calculation about a modification to the toroidal magnetic field of the Tokamak Novillo. Part I; Calculo sobre una modificacion al campo magnetico toroidal del Tokamak Novillo. Parte I

    Energy Technology Data Exchange (ETDEWEB)

    Chavez A, E.; Melendez L, L.; Colunga S, S.; Valencia A, R.; Lopez C, R.; Gaytan G, E

    1991-07-15

    The charged particles that constitute the plasma in the tokamaks are located in magnetic fields that determine its behavior. The poloidal magnetic field of the plasma current and the toroidal magnetic field of the tokamak possess relatively big gradients, which produce drifts on these particles. These drifts are largely the cause of the continuous lost of particles and of energy of the confinement region. In this work the results of numerical calculations of a modification to the 'traditional' toroidal magnetic field that one waits it diminishes the drifts by gradient and improve the confinement properties of the tokamaks. (Author)

  8. Magnetized neutron star atmospheres: beyond cool plasma approximation

    CERN Document Server

    Suleimanov, V F; Werner, K

    2012-01-01

    All the neutron star (NS) atmosphere models published so far have been calculated in the "cold plasma approximation", which neglects the relativistic effects in the radiative processes, such as cyclotron emission/absorption at harmonics of cyclotron frequency. Here we present new NS atmosphere models which include such effects. We calculate a set of models for effective temperatures T_eff =1-3 MK and magnetic fields B \\sim 10^{10}-10^{11} G, typical for the so-called central compact objects (CCOs) in supernova remnants, for which the electron cyclotron energy E_{c,e} and its first harmonics are in the observable soft X-ray range. Although the relativistic parameters, such as kT_eff /(m_e c^2) and E_{c,e} /(m_e c^2), are very small for CCOs, the relativistic effects substantially change the emergent spectra at the cyclotron resonances, E \\approx sE_{c,e} (s=1, 2,...). Although the cyclotron absorption features can form in a cold plasma due to the quantum oscillations of the free-free opacity, the shape and dep...

  9. Progress toward the creation of magnetically confined pair plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Saitoh, Haruhiko [Max-Planck-Institut fuer Plasmaphysik (Germany); The University of Tokyo (Japan); Hergenhahn, Uwe; Paschkowski, Norbert; Stanja, Juliane; Stenson, Eve V. [Max-Planck-Institut fuer Plasmaphysik (Germany); Niemann, Holger; Sunn Pedersen, Thomas [Max-Planck-Institut fuer Plasmaphysik (Germany); Ernst-Moritz-Arndt-Universitaet Greifswald (Germany); Stoneking, Matthew R. [Max-Planck-Institut fuer Plasmaphysik (Germany); Lawrence University (United States); Hugenschmidt, Christoph; Piochacz, Christian; Vohburger, Sebastian [Technische Universitaet Muenchen (Germany); Schweikhard, Lutz [Ernst-Moritz-Arndt-Universitaet Greifswald (Germany); Danielson, James R.; Surko, Clifford M. [University of California, San Diego (United States)

    2016-07-01

    The PAX (Positron Accumulation eXperiment) and APEX (A Positron Electron eXperiment) projects aim to experimentally study the unique wave propagation and stability properties of pair plasmas. We plan to accumulate a large number of positrons in a multicell-type trap system (PAX) and to confine them with electrons in APEX, a levitated dipole or stellarator configuration, operated at the NEPOMUC facility, the world's most intense positron source. In this contribution, we report on recent results from PAX and APEX. We have conducted electron experiments with a 2.3 T Penning-Malmberg trap; confinement for more than 1 hour and observation of a collective mode were demonstrated. At NEPOMUC, we have characterized the positron beam for a wide energy range. In a prototype permanent-magnet dipole trap, efficient (38%) injection of the remoderated 5 eV positron beam was realized using E x B drifts. Based on these results, design studies on the confinement of pair-plasmas in a levitated dipole trap are ongoing.

  10. Detailed Analysis Case Studies of Trapped Plasmas at the Earth’s Magnetic Equator

    Science.gov (United States)

    1993-06-01

    5 Figure 2. Plasma Density L Dependance ...... ......... 7 Figure 3. Plasmapause Magnetic Activity Dependance . . 8 Figure 4. Plasma Density L... Dependance - Normalized . . 10 Figure 5. The Dusk Bulge . . . .............. 13 Figure 6. Magnetosphere’s Electric and Magnetic Fields 14 Figure 7...1970). 6 -. ~ .ZJ.:AUGUST 12,1968 . -. ----- OUTBOUND PASS - 2 3 4 5 ___ ... 7....9 L Figure 2. Plasma Density L Dependance 7 0D3 #n /2 OUT JND tN

  11. Magnetic field generation from Self-Consistent collective neutrino-plasma interactions

    Energy Technology Data Exchange (ETDEWEB)

    Brizard, A.J.; Murayama H.; Wurtele, J.S.

    1999-11-24

    A new Lagrangian formalism for self-consistent collective neutrino-plasma interactions is presented in which each neutrino species is described as a classical ideal fluid. The neutrino-plasma fluid equations are derived from a covariant relativistic variational principle in which finite-temperature effects are retained. This new formalism is then used to investigate the generation of magnetic fields and the production of magnetic helicity as a result of collective neutrino-plasma interactions.

  12. Mechanism and scaling for convection of isolated structures in nonuniformly magnetized plasmas

    DEFF Research Database (Denmark)

    Garcia, O.E.; Bian, N.H.; Naulin, V.

    2005-01-01

    Large-scale radial advection of isolated structures in nonuniformly magnetized plasmas is investigated. The underlying mechanism considered is due to the nonlinear evolution of interchange motions, without any presumption of plasma sheaths. Theoretical arguments supported by numerical simulations...... of the structures, compares favorably with recent experimental measurements of radially propagating blob structures in the scrape-off layer of magnetically confined plasmas. (C) 2005 American Institute of Physics....

  13. Plasma confinement time in trimix-M galatea multipole magnetic trap

    Science.gov (United States)

    Bishaev, A. M.; Bugrova, A. I.; Kozintseva, M. V.; Lipatov, A. S.; Sigov, A. S.; Kharchevnikov, V. K.

    2010-05-01

    The confinement time of hydrogen plasma trapped in a Trimix-M magnetic multipole galatea was studied in a range of plasma densities (1 × 1016 - 6 × 1018 m-3) and ion energies (˜100-300 eV). It is established that (i) the confinement time increases with decreasing plasma density in the trap and (ii) as the barrier magnetic field is increased, the plasma confinement time grows faster than according to a linear law. The obtained results are indicative of a collisional character of plasma diffusion through the barrier field in the trap.

  14. STRUCTURE OF PROMINENCE LEGS: PLASMA AND MAGNETIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Levens, P. J.; Labrosse, N. [SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ (United Kingdom); Schmieder, B. [Observatoire de Paris, Meudon, F-92195 (France); Ariste, A. López, E-mail: p.levens.1@research.gla.ac.uk [Institut de Recherche en Astrophysique et Planétologie, Toulouse (France)

    2016-02-10

    We investigate the properties of a “solar tornado” observed on 2014 July 15, and aim to link the behavior of the plasma to the internal magnetic field structure of the associated prominence. We made multi-wavelength observations with high spatial resolution and high cadence using SDO/AIA, the Interface Region Imaging Spectrograph (IRIS) spectrograph, and the Hinode/Solar Optical Telescope (SOT) instrument. Along with spectropolarimetry provided by the Télescope Héliographique pour l’Etude du Magnétisme et des Instabilités Solaires telescope we have coverage of both optically thick emission lines and magnetic field information. AIA reveals that the two legs of the prominence are strongly absorbing structures which look like they are rotating, or oscillating in the plane of the sky. The two prominence legs, which are both very bright in Ca ii (SOT), are not visible in the IRIS Mg ii slit-jaw images. This is explained by the large optical thickness of the structures in Mg ii, which leads to reversed profiles, and hence to lower integrated intensities at these locations than in the surroundings. Using lines formed at temperatures lower than 1 MK, we measure relatively low Doppler shifts on the order of ±10 km s{sup −1} in the tornado-like structure. Between the two legs we see loops in Mg ii, with material flowing from one leg to the other, as well as counterstreaming. It is difficult to interpret our data as showing two rotating, vertical structures that are unrelated to the loops. This kind of “tornado” scenario does not fit with our observations. The magnetic field in the two legs of the prominence is found to be preferentially horizontal.

  15. A note on the application of the Prigogine theorem to rotation of tokamak-plasmas in absence of external torques

    Energy Technology Data Exchange (ETDEWEB)

    Sonnino, Giorgio, E-mail: gsonnino@ulb.ac.be [Department of Physics, Université Libre de Bruxelles (U.L.B.), Campus de la Plaine C.P. 231-Bvd du Triomphe, 1050 Brussels (Belgium); Royal Military Academy (RMA), Laboratory for Plasma Physics, Avenue de la Renaissance, 30, 1000 Brussels (Belgium); Cardinali, Alessandro; Zonca, Fulvio [EURATOM-ENEA Fusion Association, Via E.Fermi 45, C.P. 65-00044 Frascati, Rome (Italy); Sonnino, Alberto [Université Catholique de Louvain (UCL), Ecole Polytechnique de Louvain (EPL), Rue Archimède, 1 bte L6.11.01, 1348 Louvain-la-Neuve (Belgium); Nardone, Pasquale [Department of Physics, Université Libre de Bruxelles (U.L.B.), Campus de la Plaine C.P. 231-Bvd du Triomphe, 1050 Brussels (Belgium); Steinbrecher, György [EURATOM-MEdC Fusion Association, University of Craiova, Faculty of Exact Sciences, Str.A.I.Cuza Street 13, 200585 Craiova (Romania)

    2014-03-15

    Rotation of tokamak-plasmas, not at the mechanical equilibrium, is investigated using the Prigogine thermodynamic theorem. This theorem establishes that, for systems confined in rectangular boxes, the global motion of the system with barycentric velocity does not contribute to dissipation. This result, suitably applied to toroidally confined plasmas, suggests that the global barycentric rotations of the plasma, in the toroidal and poloidal directions, are pure reversible processes. In case of negligible viscosity and by supposing the validity of the balance equation for the internal forces, we show that the plasma, even not in the mechanical equilibrium, may freely rotate in the toroidal direction with an angular frequency, which may be higher than the neoclassical estimation. In addition, its toroidal rotation may cause the plasma to rotate globally in the poloidal direction at a speed faster than the expression found by the neoclassical theory. The eventual configuration is attained when the toroidal and poloidal angular frequencies reaches the values that minimize dissipation. The physical interpretation able to explain the reason why some layers of plasma may freely rotate in one direction while, at the same time, others may freely rotate in the opposite direction, is also provided. Invariance properties, herein studied, suggest that the dynamic phase equation might be of the second order in time. We then conclude that a deep and exhaustive study of the invariance properties of the dynamical and thermodynamic equations is the most correct and appropriate way for understanding the triggering mechanism leading to intrinsic plasma-rotation in toroidal magnetic configurations.

  16. A novel flexible field-aligned coordinate system for tokamak edge plasma simulation

    Science.gov (United States)

    Leddy, J.; Dudson, B.; Romanelli, M.; Shanahan, B.; Walkden, N.

    2017-03-01

    Tokamak plasmas are confined by a magnetic field that limits the particle and heat transport perpendicular to the field. Parallel to the field the ionised particles can move freely, so to obtain confinement the field lines are ;closed; (i.e. form closed surfaces of constant poloidal flux) in the core of a tokamak. Towards, the edge, however, the field lines intersect physical surfaces, leading to interaction between neutral and ionised particles, and the potential melting of the material surface. Simulation of this interaction is important for predicting the performance and lifetime of future tokamak devices such as ITER. Field-aligned coordinates are commonly used in the simulation of tokamak plasmas due to the geometry and magnetic topology of the system. However, these coordinates are limited in the geometry they allow in the poloidal plane due to orthogonality requirements. A novel 3D coordinate system is proposed herein that relaxes this constraint so that any arbitrary, smoothly varying geometry can be matched in the poloidal plane while maintaining a field-aligned coordinate. This system is implemented in BOUT++ and tested for accuracy using the method of manufactured solutions. A MAST edge cross-section is simulated using a fluid plasma model and the results show expected behaviour for density, temperature, and velocity. Finally, simulations of an isolated divertor leg are conducted with and without neutrals to demonstrate the ion-neutral interaction near the divertor plate and the corresponding beneficial decrease in plasma temperature.

  17. Properties of highly electronegative plasmas produced in a multipolar magnetic-confined device with a transversal magnetic filter

    DEFF Research Database (Denmark)

    Draghici, Mihai; Stamate, Eugen

    2010-01-01

    electrodes on plasma parameters, the formation of the negative ion sheath and etching rates by positive and negative ions have been investigated for different experimental conditions. When the electron temperature was reduced below 1 eV the density ratio of negative ion to electron exceeded 100 even for very......Highly electronegative plasmas were produced in Ar/SF6 gas mixtures in a dc discharge with multipolar magnetic confinement and transversal magnetic filter. Langmuir probe and mass spectrometry were used for plasma diagnostics. Plasma potential drift, the influence of small or large area biased...... low amounts of SF6 gas. The plasma potential drift could be controlled by proper wall conditioning. A large electrode biased positively had no effect on plasma potential for density ratios of negative ions to electrons larger than 50. For similar electronegativities or higher a negative ion sheath...

  18. Nonlinear electromagnetic fields in 0.5 MHz inductively coupled plasmas

    DEFF Research Database (Denmark)

    Ostrikov, K.N.; Tsakadze, E.L.; Xu, S.

    2003-01-01

    Radial profiles of magnetic fields in the electrostatic (E) and electromagnetic (H) modes of low-frequency (similar to500 kHz) inductively coupled plasmas have been measured using miniature magnetic probes. In the low-power (similar to170 W) E-mode, the magnetic field pattern is purely linear......, with the fundamental frequency harmonics only. After transition to higher-power (similar to1130 W) H-mode, the second-harmonic nonlinear azimuthal magnetic field B-phi(2omega) that is in 4-6 times larger than the fundamental frequency component B-phi(omega), has been observed. A simplified plasma fluid model...... explaining the generation of the second harmonics of the azimuthal magnetic field in the plasma source is proposed. The nonlinear second harmonic poloidal (r-z) rf current generating the azimuthal magnetic field B-phi(2omega) is attributed to nonlinear interactions between the fundamental frequency radial...

  19. PIC/MCC simulation for magnetized capacitively coupled plasmas driven by combined dc/rf sources

    Science.gov (United States)

    Yang, Shali; Zhang, Ya; Jiang, Wei; Wang, Hongyu; Wang, Shuai

    2016-09-01

    Hybrid dc/rf capacitively coupled plasma (CCP) sources have been popular in substrate etching due to their simplicity in the device structure and better plasma property. In this work, the characteristics of magnetized capacitively coupled plasmas driven by combined dc/rf sources are described by a one-dimensional Particle-in-cell/Monte Carlo collision (PIC/MCC) model. The simulation is using a rf source of 13.56MHz in argon and at a low pressure of 50mTorr. The effects of dc voltage and magnetic field on the plasmas are examined for 200-400V and 0-200Gs. It is found that, to some extent, dc voltage will increase the plasma density, but plasma density drops with increasing dc voltage. The magnetic field will enhance the plasma density significantly, due to the magnetic field will increase the electron life time and decrease the loss to the electrodes. In the bulk plasma, electron temperature is increased with the magnetic field but decreased with the dc voltage. The electron temperature in sheath is higher than in bulk plasma, due to stochastic heating in sheath is greater than Ohmic heating in bulk plasma under low gas pressure. National Natural Science Foundation of China (11405067, 11105057, 11305032, 11275039).

  20. Plasma transport in the interplanetary space: Percolation and anomalous diffusion of magnetic-field lines

    Energy Technology Data Exchange (ETDEWEB)

    Zimbardo, G.; Veltri, P. [Arcavacata di Rende, Cosenza, Univ. della Calabria (Italy). Dipt. di Fisica

    1997-11-01

    The magnetic fluctuations due to, e.g., magnetohydrodynamic turbulence cause a magnetic-field line random walk that influences many cosmic plasma phenomena. The results of a three-dimensional numerical simulation of a turbulent magnetic field in plane geometry are presented here. Magnetic percolation, Levy flights, and non-Gaussian random walk of the magnetic-field lines are found for moderate perturbation levels. In such a case plasma transport can be anomalous, i.e., either super diffusive or sub diffusive. Increasing the perturbation level a Gaussian diffusion regime is attained. The implications on the structure of the electron fore shock and of planetary magneto pauses are discussed.

  1. UHV plasma jet system for deposition of magnetic nitride nanocomposite films with GHz applications

    Energy Technology Data Exchange (ETDEWEB)

    Fendrych, F; Lancok, A [Institute of Physics, Academy of Sciences, Na Slovance 2, CZ-18221 Prague 8 (Czech Republic); Repa, P; Peksa, L; Gronych, T; Vejpravova, J P [Faculty of Math and Physics, Charles University in Prague, V Holesovickach 2, CZ-18000 Prague 8 (Czech Republic); Hedbavny, P [VAKUUM PRAHA, V Holesovickach 2, CZ-18000 Prague 8 (Czech Republic); Schaefer, R [Leibniz Institute IFW Dresden, Helmholtzstr. 20, D-01069 Dresden (Germany); Seemann, K M [Forschungszentrum Karlsruhe, Eggenstein, D-76021 Karlsruhe (Germany)], E-mail: fendrych@fzu.cz

    2008-03-15

    A method of preparation of extremely pure magnetic thin films, especially magnetic nitride nanocomposites for GHz aplications was searched. The plasma-jet method was chosen for its advantages at magnetic materials deposition. Sources of impurities deteriorating the quality of the films were analysed. Based on the assumption that the achievable purity is limited mainly by the conditions at the deposition, an experimental UHV apparatus with the plasma-jet was designed. A number of magnetic thin films from various materials including nitride nanocomposite films was prepared already in this apparatus at UHV conditions. Their magnetic properties are far better than those of the films prepared in a high vacuum apparatus.

  2. Fundamental Statistical Descriptions of Plasma Turbulence in Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    John A. Krommes

    2001-02-16

    A pedagogical review of the historical development and current status (as of early 2000) of systematic statistical theories of plasma turbulence is undertaken. Emphasis is on conceptual foundations and methodology, not practical applications. Particular attention is paid to equations and formalism appropriate to strongly magnetized, fully ionized plasmas. Extensive reference to the literature on neutral-fluid turbulence is made, but the unique properties and problems of plasmas are emphasized throughout. Discussions are given of quasilinear theory, weak-turbulence theory, resonance-broadening theory, and the clump algorithm. Those are developed independently, then shown to be special cases of the direct-interaction approximation (DIA), which provides a central focus for the article. Various methods of renormalized perturbation theory are described, then unified with the aid of the generating-functional formalism of Martin, Siggia, and Rose. A general expression for the renormalized dielectric function is deduced and discussed in detail. Modern approaches such as decimation and PDF methods are described. Derivations of DIA-based Markovian closures are discussed. The eddy-damped quasinormal Markovian closure is shown to be nonrealizable in the presence of waves, and a new realizable Markovian closure is presented. The test-field model and a realizable modification thereof are also summarized. Numerical solutions of various closures for some plasma-physics paradigms are reviewed. The variational approach to bounds on transport is developed. Miscellaneous topics include Onsager symmetries for turbulence, the interpretation of entropy balances for both kinetic and fluid descriptions, self-organized criticality, statistical interactions between disparate scales, and the roles of both mean and random shear. Appendices are provided on Fourier transform conventions, dimensional and scaling analysis, the derivations of nonlinear gyrokinetic and gyrofluid equations

  3. Three-dimensional simulation study of compact toroid plasmoid injection into magnetized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Y.; Watanabe, T.-H.; Sato, T.; Hayashi, T. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    1999-04-01

    Three-dimensional dynamics of a compact toroid (CT) plasmoid, which is injected into a magnetized target plasma region is investigated by using magnetohydrodynamic (MHD) numerical simulations. It is found that the process of the CT penetration into this region is much more complicated than what has been analyzed so far by using a conducting sphere (CS) model. The injected CT suffers from a tilting instability, which grows with the similar time scale as the CT penetration. The instability is accompanied by magnetic reconnection between the CT magnetic field and the target magnetic field, which disrupts the magnetic configuration of the CT. Magnetic reconnection plays a role to supply the high density plasma initially confined in the CT magnetic field into the target region. Also, the penetration depth of the CT high density plasma is examined. It is shown to be shorter than that estimated from the CS model. The CT high density plasma is decelerated mainly by the Lorentz force of the target magnetic field, which includes not only the magnetic pressure force but also the magnetic tension force. Furthermore, by comparing the CT plasmoid injection with the bare plasmoid injection, magnetic reconnection is considered to relax the magnetic tension force, that is the deceleration of the CT plasmoid. (author)

  4. Investigating plasma motion of magnetic clouds at 1 AU through a velocity-modified cylindrical force-free flux rope model

    CERN Document Server

    Wang, Yuming; Shen, Chenglong; Liu, Rui; Wang, S

    2015-01-01

    Magnetic clouds (MCs) are the interplanetary counterparts of coronal mass ejections (CMEs), and usually modeled by a flux rope. By assuming the quasi-steady evolution and self-similar expansion, we introduce three types of global motion into a cylindrical force-free flux rope model, and developed a new velocity-modified model for MCs. The three types of the global motion are the linear propagating motion away from the Sun, the expanding and the poloidal motion with respect to the axis of the MC. The model is applied to 72 MCs observed by Wind spacecraft to investigate the properties of the plasma motion of MCs. First, we find that some MCs had a significant propagation velocity perpendicular to the radial direction, suggesting the direct evidence of the CME's deflected propagation and/or rotation in interplanetary space. Second, we confirm the previous results that the expansion speed is correlated with the radial propagation speed and most MCs did not expand self-similarly at 1 AU. In our statistics, about 6...

  5. Study of magnetic field expansion using a plasma generator for space radiation active protection

    Institute of Scientific and Technical Information of China (English)

    JIA Xiang-Hong; JIA Shao-Xia; XU Feng; BAI Yan-Qiang; WAN Jun; LIU Hong-Tao; JIANG Rui

    2013-01-01

    There are many active protecting methods including Electrostatic Fields,Confined Magnetic Field,Unconfined Magnetic Field and Plasma Shielding etc.for defending the high-energy solar particle events (SPE) and Galactic Cosmic Rays (GCR) in deep space exploration.The concept of using cold plasma to expand a magnetic field is the best one of all possible methods so far.The magnetic field expansion caused by plasma can improve its protective efficiency of space particles.One kind of plasma generator has been developed and installed into the cylindrical permanent magnet in the eccentric.A plasma stream is produced using a helical-shaped antenna driven by a radio-frequency (RF) power supply of 13.56 MHz,which exits from both sides of the magnet and makes the magnetic field expand on one side.The discharging belts phenomenon is similar to the Earth's radiation belt,but the mechanism has yet to be understood.A magnetic probe is used to measure the magnetic field expansion distributions,and the results indicate that the magnetic field intensity increases under higher increments of the discharge power.

  6. Terrace retro-reflector array for poloidal polarimeter on ITER.

    Science.gov (United States)

    Imazawa, R; Kawano, Y; Ono, T; Kusama, Y

    2011-02-01

    A new concept of a terrace retro-reflector array (TERRA) as part of the poloidal polarimeter for ITER is proposed in this paper. TERRA reflects a laser light even from a high incident angle in the direction of the incident-light path, while a conventional retro-reflector array cannot. Besides, TERRA can be installed in a smaller space than a corner-cube retro-reflector. In an optical sense, TERRA is equivalent to a Littrow grating, the blaze angle of which varies, depending on the incident angle. The reflected light generates a bright and dark fringe, and the bright fringe is required to travel along the incident-light path to achieve the objects of laser-aided diagnostics. In order to investigate the propagation properties of laser light reflected by TERRA, we have developed a new diffraction formula. Conditions for the propagation of the bright fringe in the direction of the incident light have been obtained using the Littrow grating model and have been confirmed in a simulation applying the new diffraction formula. Finally, we have designed laser transmission optics using TERRA for the ITER poloidal polarimeter and have calculated the light propagation of the system. The optical design obtains a high transmission efficiency, with 88.6% of the incident power returned. These results demonstrate the feasibility of applying TERRA to the ITER poloidal polarimeter.

  7. Influence of magnetic field on microstructure and properties of Ni60 plasma surfacing layer

    Institute of Scientific and Technical Information of China (English)

    Liu Zhengjun; Sun Jinggang; Liu Duo; Wang Jibing; Zhang Guiqing

    2005-01-01

    In order to control the shape and distribution of hardening phase in plasma surfacing deposit, a longitudinal DC magnetic field was applied during plasma surfacing of nickel-based alloy Ni60. Hardness, wearing resistance, microstructure and phase constituent of the plasma surfacing layer were investigated. It was revealed that the hardness and wearing resistance of the Ni60 plasma surfacing layer could gotten significantly enhanced through introducing magnetic field. The mechanical properties of the surfacing deposit were optimal when magnetic field current is 1 A. The metallurgical analysis showed that the microstructure of the Ni60 plasma surfacing layer was mainly composed of γ solid solution and some hardening phase particles such as Cr7 C3 with an application of the magnetic field.

  8. Persistence of magnetic field driven by relativistic electrons in a plasma

    CERN Document Server

    Flacco, A; Lifschitz, A; Sylla, F; Kahaly, S; Veltcheva, M; Silva, L O; Malka, V

    2015-01-01

    The onset and evolution of magnetic fields in laboratory and astrophysical plasmas is determined by several mechanisms, including instabilities, dynamo effects and ultra-high energy particle flows through gas, plasma and interstellar-media. These processes are relevant over a wide range of conditions, from cosmic ray acceleration and gamma ray bursts to nuclear fusion in stars. The disparate temporal and spatial scales where each operates can be reconciled by scaling parameters that enable to recreate astrophysical conditions in the laboratory. Here we unveil a new mechanism by which the flow of ultra-energetic particles can strongly magnetize the boundary between the plasma and the non-ionized gas to magnetic fields up to 10-100 Tesla (micro Tesla in astrophysical conditions). The physics is observed from the first time-resolved large scale magnetic field measurements obtained in a laser wakefield accelerator. Particle-in-cell simulations capturing the global plasma and field dynamics over the full plasma le...

  9. TIME DOMAIN ANALYSIS OF TRANSIENT PROPAGATION IN INHOMOGENEOUS MAGNETIZED PLASMA USING Z-TRANSFORMS

    Institute of Scientific and Technical Information of China (English)

    Huang Shoujiang; Li Fang

    2006-01-01

    The electromagnetic propagation through an inhomogeneous magnetized plasma slab is studied using the Z-transform formulation of the Finite-Difference Time-Domain(FDTD) method. The direction of electromagnetic propagation is parallel to the biasing magnetic filed. To validate the Z-transform algorithm, the reflection and transmission coefficients for the right-hand circularly polarized wave of the homogeneous magnetized plasma slab are computed by means of discrete Fourier transform. The comparison between the reflection and transmission coefficients of the homogeneous plasma slab and analytical values indicates that Z-transform algorithm is very accurate. When the plasma frequency varies according to the square root and parabolic relations, the reflection and transmission coefficients of the inhomogeneous magnetized plasma slab are computed.

  10. Statistics of magnetic field fluctuations in a partially ionized space plasma

    Energy Technology Data Exchange (ETDEWEB)

    Shaikh, Dastgeer, E-mail: dastgeer.shaikh@uah.ed [Department of Physics and Center for Space Plasma and Aeronomy Research, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

    2010-07-05

    Voyager 1 and 2 data reveals that magnetic field fluctuations are compressive and exhibit a Gaussian distribution in the compressed heliosheath plasma, whereas they follow a lognormal distribution in a nearly incompressible supersonic solar wind plasma. To describe the evolution of magnetic field, we develop a nonlinear simulation model of a partially ionized plasma based on two-dimensional time-dependent multifluid model. Our model self-consistently describes solar wind plasma ions, electrons, neutrals and pickup ions. It is found from our simulations that the magnetic field evolution is governed by mode conversion process that leads to the suppression of vortical modes, whereas the compressive modes are amplified. An implication of the mode conversion process is to quench the Alfvenic interactions associated with the vortical motions. Consequently anisotropic cascades are reduced. This is accompanied by the amplification of compressional modes that tend to isotropize the plasma fluctuations and lead to a Gaussian distribution of the magnetic field.

  11. Development of a new experimental device for long-duration magnetic reconnection in weakly ionized plasma

    Science.gov (United States)

    Yanai, Ryoma; Kaminou, Yasuhiro; Nishida, Kento; Inomoto, Michiaki

    2016-10-01

    Magnetic reconnection is a universal phenomenon which determines global structure and energy conversion in magnetized plasmas. Many experimental studies have been carried out to explore the physics of magnetic reconnection in fully ionized condition. However, it is predicted that the behavior of magnetic reconnection in weakly ionized plasmas such as solar chromosphere plasma will show different behavior such as ambipolar diffusion caused by interaction with neutral particles. In this research, we are developing a new experimental device to uncover the importance of ambipolar diffusion during magnetic reconnection in weakly ionized plasmas. We employ an inverter-driven rotating magnetic fields technique, which is used for generating steady azimuthal plasma current, to establish long-duration ( 1 ms) anti-parallel reconnection with magnetic field of 5 mT in weakly ionized plasma. We will present development status and initial results from the new experimental setup. This work was supported by JSPS A3 Foresight Program ``Innovative Tokamak Plasma Startup and Current Drive in Spherical Torus'', Giant-in Aid for Scientific Research (KAKENHI) 15H05750, 15K14279, 26287143 and the NIFS Collaboration Research program (NIFS14KNWP004).

  12. 3D Kinetic Simulation of Plasma Jet Penetration in Magnetic Field

    Science.gov (United States)

    Galkin, Sergei A.; Bogatu, I. N.; Kim, J. S.

    2009-11-01

    A high velocity plasmoid penetration through a magnetic barrier is a problem of a great experimental and theoretical interest. Our LSP PIC code 3D fully kinetic numerical simulations of high density (10^16 cm-3) high velocity (30-140 km/sec) plasma jet/bullet, penetrating through the transversal magnetic field, demonstrate three different regimes: reflection by field, penetration by magnetic field expulsion and penetration by magnetic self-polarization. The behavior depends on plasma jet parameters and its composition: hydrogen, carbon (A=12) and C60-fullerene (A=720) plasmas were investigated. The 3D simulation of two plasmoid head-on injections along uniform magnetic field lines is analyzed. Mini rail plasma gun (accelerator) modeling is also presented and discussed.

  13. Rayleigh-Taylor-Instability Evolution in Colliding-Plasma-Jet Experiments with Magnetic and Viscous Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Colin Stuart [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States)

    2015-01-15

    The Rayleigh-Taylor instability causes mixing in plasmas throughout the universe, from micron-scale plasmas in inertial confinement fusion implosions to parsec-scale supernova remnants. The evolution of this interchange instability in a plasma is influenced by the presence of viscosity and magnetic fields, both of which have the potential to stabilize short-wavelength modes. Very few experimental observations of Rayleigh-Taylor growth in plasmas with stabilizing mechanisms are reported in the literature, and those that are reported are in sub-millimeter scale plasmas that are difficult to diagnose. Experimental observations in well-characterized plasmas are important for validation of computational models used to make design predictions for inertial confinement fusion efforts. This dissertation presents observations of instability growth during the interaction between a high Mach-number, initially un-magnetized plasma jet and a stagnated, magnetized plasma. A multi-frame fast camera captures Rayleigh-Taylor-instability growth while interferometry, spectroscopy, photodiode, and magnetic probe diagnostics are employed to estimate plasma parameters in the vicinity of the collision. As the instability grows, an evolution to longer mode wavelength is observed. Comparisons of experimental data with idealized magnetohydrodynamic simulations including a physical viscosity model suggest that the observed instability evolution is consistent with both magnetic and viscous stabilization. These data provide the opportunity to benchmark computational models used in astrophysics and fusion research.

  14. Rayleigh-Taylor-instability evolution in colliding-plasma-jet experiments with magnetic and viscous stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Colin Stuart [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States); Univ. of Washington, Seattle, WA (United States)

    2015-01-15

    The Rayleigh-Taylor instability causes mixing in plasmas throughout the universe, from micron-scale plasmas in inertial confinement fusion implosions to parsec-scale supernova remnants. The evolution of this interchange instability in a plasma is influenced by the presence of viscosity and magnetic fields, both of which have the potential to stabilize short-wavelength modes. Very few experimental observations of Rayleigh-Taylor growth in plasmas with stabilizing mechanisms are reported in the literature, and those that are reported are in sub-millimeter scale plasmas that are difficult to diagnose. Experimental observations in well-characterized plasmas are important for validation of computational models used to make design predictions for inertial confinement fusion efforts. This dissertation presents observations of instability growth during the interaction between a high Mach-number, initially un-magnetized plasma jet and a stagnated, magnetized plasma. A multi-frame fast camera captures Rayleigh-Taylor-instability growth while interferometry, spectroscopy, photodiode, and magnetic probe diagnostics are employed to estimate plasma parameters in the vicinity of the collision. As the instability grows, an evolution to longer mode wavelength is observed. Comparisons of experimental data with idealized magnetohydrodynamic simulations including a physical viscosity model suggest that the observed instability evolution is consistent with both magnetic and viscous stabilization. These data provide the opportunity to benchmark computational models used in astrophysics and fusion research.

  15. Non-modal stability analysis and transient growth in a magnetized Vlasov plasma

    CERN Document Server

    Ratushnaya, Valeria

    2014-01-01

    Collisionless plasmas, such as those encountered in tokamaks, exhibit a rich variety of instabilities. The physical origin, triggering mechanisms and fundamental understanding of many plasma instabilities, however, are still open problems. We investigate the stability properties of a collisionless Vlasov plasma in a stationary homogeneous magnetic field. We narrow the scope of our investigation to the case of Maxwellian plasma. For the first time using a fully kinetic approach we show the emergence of the local instability, a transient growth, followed by classical Landau damping in a stable magnetized plasma. We show that the linearized Vlasov operator is non-normal leading to the algebraic growth of the perturbations using non-modal stability theory. The typical time scales of the obtained instabilities are of the order of several plasma periods. The first-order distribution function and the corresponding electric field are calculated and the dependence on the magnetic field and perturbation parameters is s...

  16. Neutral Beam Injection for Plasma and Magnetic FieldDiagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Vainionpaa, Jaakko Hannes; Leung, Ka Ngo; Kwan, Joe W.; Levinton,Fred

    2007-08-01

    At the Lawrence Berkeley National Laboratory (LBNL) adiagnostic neutral beam injection system for measuring plasma parameters,flow velocity, and local magnetic field is being developed. High protonfraction and small divergence is essential for diagnostic neutral beams.In our design, a neutral hydrogen beam with an 8 cm x 11 cm (or smaller)elliptical beam spot at 2.5 m from the end of the extraction column isproduced. The beam will deliver up to 5 A of hydrogen beam to the targetwith a pulse width of ~;1 s, once every 1 - 2 min. The H1+ ion species ofthe hydrogen beamwill be over 90 percent. For this application, we havecompared two types of RF driven multicusp ion sources operating at 13.56MHz. The first one is an ion source with an external spiral antennabehind a dielectric RF-window. The second one uses an internal antenna insimilar ion source geometry. The source needs to generate uniform plasmaover a large (8 cm x 5 cm) extraction area. We expect that the ion sourcewith internal antenna will be more efficient at producing the desiredplasma density but might have the issue of limited antenna lifetime,depending on the duty factor. For both approaches there is a need forextra shielding to protect the dielectric materials from the backstreaming electrons. The source walls will be made of insulator materialsuch as quartz that has been observed to generate plasma with higheratomic fraction than sources with metal walls. The ion beam will beextracted and accelerated by a set of grids with slits, thus forming anarray of 6 sheet-shaped beamlets. The multiple grid extraction will beoptimized using computer simulation programs. Neutralization of the beamwill be done in neutralization chamber, which has over 70 percentneutralization efficiency.

  17. Synthesis of magnetic nanoparticles by atmospheric-pressure glow discharge plasma-assisted electrolysis

    Science.gov (United States)

    Shirai, Naoki; Yoshida, Taketo; Uchida, Satoshi; Tochikubo, Fumiyoshi

    2017-07-01

    For the synthesis of magnetic nanoparticles (NPs), we used plasma-assisted electrolysis in which atmospheric-pressure DC glow discharge using a liquid electrode is combined with electrolysis. The solution surface is exposed to positive ions or electrons in plasma. To synthesize magnetic NPs, aqueous solutions of FeCl2 or an iron electrode immersed in liquid was used to supply iron ions in the liquid. Magnetic NPs were synthesized at the plasma-liquid interface upon the electron irradiation of the liquid surface. In the case of using aqueous solutions of FeCl2, the condition of magnetic NP synthesis depended on the gas species of plasma and the chemical agent in the liquid for controlling oxidization. The amount of magnetic NPs synthesized using plasma is not very large. On the other hand, in the case of using an iron electrode immersed in NaCl solution, magnetic NPs were synthesized without using FeCl2 solutions. When plasma-assisted electrolysis was operated, the iron electrode eluted Fe cations, resulting in the formation of magnetic NPs at the plasma-liquid interface. Magnetic NP synthesis depended on the concentration of NaCl solution and discharge current. The magnetic NPs were identified to be magnetite. By using this method, more magnetite NPs were synthesized than in the case of plasma-assisted electrolysis with FeCl2 aqueous solutions. The pH of the liquid used in plasma-assisted electrolysis was important for the synthesis of magnetite NPs.

  18. Heat treatment process of new NdFeB magnet prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    李涛; 岳明; 张久兴; 王公平; 肖耀福; 王润

    2003-01-01

    In recent years, spark plasma sintering technique(SPS) has been a focus in the field of material preparation due to its advantages. SPS technique is first introduced for preparation of high quality NdFeB magnets. The effects of heat treatment process on the magnetic properties of SPS NdFeB magnet were investigated. Meanwhile, the effects of heat treatment process on the microstructure, tropism and dimensional precision of the SPS NdFeB magnets were also studied. The high quality NdFeB magnets with fine grains were prepared under proper heat treatment process. The results show that the magnetic properties of SPS NdFeB can be further improved through proper heat treatment process. Meanwhile, the experiment also demonstrates that it is feasible to prepare near-net-shape NdFeB magnets with fine grains and high magnetic property by spark plasma sintering.

  19. Ion-wake-mediated particle interaction in a magnetized-plasma flow.

    Science.gov (United States)

    Carstensen, Jan; Greiner, Franko; Piel, Alexander

    2012-09-28

    The interaction forces between dust grains in a flowing plasma are strongly modified by the formation of ion wakes. Here, we study the interparticle forces mediated by ion wakes in the presence of a strong magnetic field parallel to the ion flow. For increasing magnetic flux densities a continuous decay of the interaction force is observed. This transition occurs at parameters, where the ion cyclotron frequency starts to exceed the ion plasma frequency, which is in agreement with theoretical predictions. The modification of the interparticle forces is important for the understanding of the structure and dynamics of magnetized dusty plasmas.

  20. Study of periodic band gap structure of the magnetized plasma photonic crystals

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hai-feng; MA Li; LIU Shao-bin

    2009-01-01

    The characteristics of the periodic band gaps of the one dimension magnetized plasma photonic crystals are studied with the piecewise linear current density recursive convolution (PLCDRC) finite-differential time-domain (FDTD) method. In fre-quency-domain, the transmission coefficients of electromagnetic Gaussian pulses are computed, and the effects of the periodic structure constant, plasma layer thickness and parameters of plasma on the properties of periodic band gaps of magnetized photonic crystals are analyzed. The results show that the periodic band gaps depend strongly on the plasma parameters.

  1. Particle Acceleration and Plasma Dynamics during Magnetic Reconnection in the Magnetically-dominated Regime

    CERN Document Server

    Guo, Fan; Daughton, William; Li, Hui

    2015-01-01

    Magnetic reconnection is thought to be the driver for many explosive phenomena in the universe. The energy release and particle acceleration during reconnection have been proposed as a mechanism for producing high-energy emissions and cosmic rays. We carry out two- and three-dimensional kinetic simulations to investigate relativistic magnetic reconnection and the associated particle acceleration. The simulations focus on electron-positron plasmas starting with a magnetically dominated, force-free current sheet ($\\sigma \\equiv B^2/(4\\pi n_e m_e c^2) \\gg 1$). For this limit, we demonstrate that relativistic reconnection is highly efficient at accelerating particles through a first-order Fermi process accomplished by the curvature drift of particles along the electric field induced by the relativistic flows. This mechanism gives rise to the formation of hard power-law spectra $f \\propto (\\gamma-1)^{-p}$ and approaches $p = 1$ for sufficiently large $\\sigma$ and system size. Eventually most of the available magne...

  2. LabVIEW software for analyzing Langmuir probe characteristics in magnetized plasma

    Science.gov (United States)

    Gandhi, S.; Binwal, S.; Kabariya, H.; Karkari, S. K.

    2016-03-01

    This paper describes the methodology for processing Ampere-Volts (I-V) characteristics of the Langmuir probe in magnetized plasma using graphical programming language based on LabVIEW. Computing the plasma parameters from I-V characteristic involves several steps that include signal processing, interpolation, linear and non-linear curve fitting based on physical models, finding the derivatives of the experimental curve and determining the zero-crossing of the probe current as a function of the applied voltage. These operations are practically tedious to perform manually causing systematic errors in output parameters. To overcome this challenge, software is developed to analyze the planar Langmuir probe characteristics in magnetized plasma. The software allows simultaneous display of different plasma parameters that helps to verify the consistency of the analyzed plasma parameters with the standard probe theory. Using this software, plasma parameters are obtained in a linear plasma device and its characteristics are discussed.

  3. One-photon pair annihilation in magnetized relativistic plasmas

    Science.gov (United States)

    Harding, A. K.

    1986-01-01

    In supersonic magnetic fields, electron-positron pairs may annihilate into single photons producing spectral features above 1 MeV. The paper calculates the exact one-photon annihilation rate in the general case where pairs may annihilate from excited Landau states, extending the previous studies which were restricted to pairs in the ground state. Asymptotic expressions for annihilation spectra and rates in the limit of large pair quantum numbers are also derived. It is found that the rate of annihilation from excited states can exceed the rate from the ground state by orders of magnitude in fields less than about 2 x 10 to the 12th G. This allows one-photon annihilation to be competitive with the two-photon process at typical neutron star field strengths. Annihilation spectra from a Maxwellian pair plasma at transrelativistic temperatures show fine structure near threshold on a scale (h/2pi)omega sub B as the result of contributions from individual pair states, which blend into a smooth continuum at higher energies.

  4. Studies of Dynamic, Radiative Macroscopic Magnetized HED Plasmas with Closed B-Field Lines

    Energy Technology Data Exchange (ETDEWEB)

    Frese, Michael H. [NumerEx, LLC, Albuquerque, NM (United States); Frese, Sherry D. [NumerEx, LLC, Albuquerque, NM (United States)

    2013-11-01

    The purpose of this research has been to study the physics of macroscopic magnetized high-energy-density laboratory plasmas (HEDLPs) created through the compression of a high-beta compact toroid (CT) plasma having closed magnetic field lines. The high-beta CT chosen for this work is a field-reversed configuration (FRC). The basic approach is to investigate CT plasmas as they are compressed to a HED state by the electromagnetic implosion of a surrounding metallic shell or solid liner (Figure 1). The shell provides an axisymmetric, electrically-conducting boundary around the plasma and its supporting magnetic field and is imploded by means of the magnetic pressure force arising from axial current flow in the liner interacting with its associated azimuthal magnetic field. Compression of the CT will bring the plasma to fusion temperatures at higher densities and magnetic fields (multi-MegaGauss [MG]) than have previously been present in conventional magnetic fusion approaches. The resulting energy densities will be ~1 Mbar or greater and thus will place the plasma in a parameter space intermediate to MFE and IFE. This work has been a collaboration between the Air Force Research Laboratory, Los Alamos National Laboratory, and NumerEx, LLC.

  5. Electron acceleration in collisionless shocks and magnetic reconnection by laser-produced plasma ablation

    Science.gov (United States)

    Park, Jaehong; Spitkovksy, Anatoly; Fox, Will; Bhattacharjee, Amitava

    2016-10-01

    We perform particle-in-cell simulations of collisionless shocks and magnetic reconnection generated by ablated plasma expanding into a magnetized background plasma. We find: (1) The simulated proton radiography produces different morphology of the shock structure depending on the orientation of the magnetic field and can be used to identify a shock in the experiment. Electrons are accelerated by the whistler waves generated at oblique sites of the shock. (2) Forced collisionless magnetic reconnection is induced when the expanding plumes carry opposite magnetic polarities and interact with a background plasma. Electrons are accelerated at the reconnection X line and reveal a power-law distribution as the plasma beta is lowered, β = 0.08 . As the plasma beta is increased, β = 0.32 , the 1st order Fermi mechanism against the two plasma plumes contributes to the electron acceleration as well as the X line acceleration. Using 3-D simulations, we also explore the effect of 3-D instabilities (Weibel instability or drift-kink) on particle acceleration and magnetic field annihilation between the colliding magnetized plumes

  6. Oscillations of Magnetized Dust Grains in Plasma Sheath with Negative Ions

    Institute of Scientific and Technical Information of China (English)

    GAN Bao-Xia; CHEN Yin-Hua

    2007-01-01

    The oscillations of a single magnetized dust grain in electronegative plasma sheath are investigated taking into account the existence of an external magnetic field. The influence of the content of negative ions and the magnetic field intensity on the properties of the dust vibration is analysed. The result shows that the existence of the negative ions in plasma reduces the dust oscillation frequency and drops the equilibrium position of dust, whereas the magnetic field raises the equilibrium position and also reduces the dust oscillation frequency on the condition considered.

  7. Small amplitude nonlinear electron acoustic solitary waves in weakly magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Manjistha; Khan, Manoranjan [Department of Instrumentation Science, Jadavpur University, Kolkata-700 032 (India); Ghosh, Samiran [Department of Applied Mathematics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata-700 009 (India); Roychoudhury, Rajkumar [Indian Statistical Institute, Kolkata-700 108 (India); Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar Kolkata-700 064 (India)

    2013-01-15

    Nonlinear propagation of electron acoustic waves in homogeneous, dispersive plasma medium with two temperature electron species is studied in presence of externally applied magnetic field. The linear dispersion relation is found to be modified by the externally applied magnetic field. Lagrangian transformation technique is applied to carry out nonlinear analysis. For small amplitude limit, a modified KdV equation is obtained, the modification arising due to presence of magnetic field. For weakly magnetized plasma, the modified KdV equation possesses stable solitary solutions with speed and amplitude increasing temporally. The solutions are valid upto some finite time period beyond which the nonlinear wave tends to wave breaking.

  8. Fast magnetic field annihilation driven by two laser pulses in underdense plasma

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Y. J.; Kumar, D.; Weber, S.; Korn, G. [Institute of Physics of the ASCR, ELI-Beamlines, 18221 Prague (Czech Republic); Klimo, O. [Institute of Physics of the ASCR, ELI-Beamlines, 18221 Prague (Czech Republic); FNSPE, Czech Technical University in Prague, 11519 Prague (Czech Republic); Bulanov, S. V.; Esirkepov, T. Zh. [Kansai Photon Science Institute, Japan Atomic Energy Agency, 8-1-7 Umemidai, Kizugawa-shi, Kyoto 619-0215 (Japan)

    2015-10-15

    Fast magnetic annihilation is investigated by using 2.5-dimensional particle-in-cell simulations of two parallel ultra-short petawatt laser pulses co-propagating in underdense plasma. The magnetic field generated by the laser pulses annihilates in a current sheet formed between the pulses. Magnetic field energy is converted to an inductive longitudinal electric field, which efficiently accelerates the electrons of the current sheet. This new regime of collisionless relativistic magnetic field annihilation with a timescale of tens of femtoseconds can be extended to near-critical and overdense plasma with the ultra-high intensity femtosecond laser pulses.

  9. Measurement of hot electron transport in overdense plasma VIA self induced giant magnetic pulses

    Science.gov (United States)

    Mondal, S.; Narayanan, V.; Lad, Amit D.; Ahmed, Saima; Sengupta, S.; Das, A.; Sheng, Z. M.; Kaw, P. K.; Kumar, G. Ravindra

    2010-08-01

    Spatial and temporal resolved ultrashort(8ps) multimegagauss(65 MG) magnetic field has been measured in plasma produced on Al-coated BK-7 glass by the interaction of a relativististic intensity laser(4x1018W/cm2, 30 fs) using pump-probe polarimetry. The 2D profile of magnetic field is captured using a CCD camera. Mapping of this magnetic field maps the transport of relativistic electrons in the plasma. The magnetic field profiles indicate filamentary behavior (Weibel-like instability). Particle in cell simulation are used to explain the result obtained.

  10. Tokamak Plasmas : Mirnov coil data analysis for tokamak ADITYA

    Indian Academy of Sciences (India)

    D Raju; R Jha; P K Kaw; S K Mattoo; Y C Saxena; Aditya Team

    2000-11-01

    The spatial and temporal structures of magnetic signal in the tokamak ADITYA is analysed using recently developed singular value decomposition (SVD) technique. The analysis technique is first tested with simulated data and then applied to the ADITYA Mirnov coil data to determine the structure of current peturbation as the discharge progresses. It is observed that during the current rise phase, current perturbation undergoes transition from = 5 poloidal structure to = 4 and then to = 3. At the time of current termination, = 2 perturbation is observed. It is observed that the mode frequency remains nearly constant (≈10 kHz) when poloidal mode structure changes from = 4 to = 2. This may be either an indication of mode coupling or a consequences of changes in the plasma electron temperature and density scale length.

  11. Comment on "Surface electromagnetic wave equations in a warm magnetized quantum plasma" [Phys. Plasmas 21, 072114 (2014)

    Science.gov (United States)

    Moradi, Afshin

    2016-07-01

    In a recent article [C. Li et al., Phys. Plasmas 21, 072114 (2014)], Li et al. studied the propagation of surface waves on a magnetized quantum plasma half-space in the Voigt configuration (in this case, the magnetic field is parallel to the surface but is perpendicular to the direction of propagation). Here, we present a fresh look at the problem and obtain a new form of dispersion relation of surface waves of the system. We find that our new dispersion relation does not agree with the result obtained by Li et al.

  12. Heavy ion beam probing—diagnostics to study potential and turbulence in toroidal plasmas

    Science.gov (United States)

    Melnikov, A. V.; Krupnik, L. I.; Eliseev, L. G.; Barcala, J. M.; Bravo, A.; Chmyga, A. A.; Deshko, G. N.; Drabinskij, M. A.; Hidalgo, C.; Khabanov, P. O.; Khrebtov, S. M.; Kharchev, N. K.; Komarov, A. D.; Kozachek, A. S.; Lopez, J.; Lysenko, S. E.; Martin, G.; Molinero, A.; de Pablos, J. L.; Soleto, A.; Ufimtsev, M. V.; Zenin, V. N.; Zhezhera, A. I.; T-10 Team; TJ-II Team

    2017-07-01

    Heavy ion beam probing (HIBP) is a unique diagnostics to study the core plasma potential and turbulence. Advanced HIBPs operate in the T-10 tokamak and TJ-II flexible heliac with fine focused (magnetic configurations with ECR and neutral beam injection (NBI) heating at TJ-II. Time evolution of the radial profiles and/or local values of plasma parameters from high field side (HFS) to low field side (LFS), -1  magnetic field B pol (by the beam toroidal shift), poloidal electric filed E pol that allows one to derive the electrostatic turbulent particle flux ΓE×B. The cross-phase of density oscillations produces the phase velocity of their poloidal propagation or rotation; also it gives the poloidal mode number. Dual HIBP, consisting of two identical HIBPs located ¼ torus apart provide the long-range correlations of core plasma parameters. Low-noise high-gain electronics allows us to study broadband turbulence and quasi-coherent modes like geodesic acoustic modes and Alfvén eigenmodes.

  13. Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Amitava, E-mail: roy@fzu.cz, E-mail: aroy@barc.gov.in [School of Nuclear Engineering and Center for Materials Under Extreme Environment(CMUXE), Purdue University, West Lafayette, Indiana 47907 (United States); HiLASE Project, Department of Diode-pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague (Czech Republic); Murtaza Hassan, Syed; Harilal, Sivanandan S.; Hassanein, Ahmed [School of Nuclear Engineering and Center for Materials Under Extreme Environment(CMUXE), Purdue University, West Lafayette, Indiana 47907 (United States); Endo, Akira; Mocek, Tomas [HiLASE Project, Department of Diode-pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague (Czech Republic)

    2014-05-15

    We investigated the role of a guiding magnetic field on extreme ultraviolet (EUV) and ion emission from a laser produced Sn plasma for various laser pulse duration and intensity. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm, Nd:YAG laser pulses with varying pulse duration (5–15 ns) and intensity. A magnetic trap was fabricated with the use of two neodymium permanent magnets which provided a magnetic field strength ∼0.5 T along the plume expansion direction. Our results indicate that the EUV conversion efficiency do not depend significantly on applied axial magnetic field. Faraday Cup ion analysis of Sn plasma show that the ion flux reduces by a factor of ∼5 with the application of an axial magnetic field. It was found that the plasma plume expand in the lateral direction with peak velocity measured to be ∼1.2 cm/μs and reduced to ∼0.75 cm/μs with the application of an axial magnetic field. The plume expansion features recorded using fast photography in the presence and absence of 0.5 T axial magnetic field are simulated using particle-in-cell code. Our simulation results qualitatively predict the plasma behavior.

  14. Hermes: Global plasma edge fluid turbulence simulations

    CERN Document Server

    Dudson, Ben

    2016-01-01

    The transport of heat and particles in the relatively collisional edge regions of magnetically confined plasmas is a scientifically challenging and technologically important problem. Understanding and predicting this transport requires the self-consistent evolution of plasma fluctuations, global profiles and flows, but the numerical tools capable of doing this in realistic (diverted) geometry are only now being developed. Here a 5-field reduced 2-fluid plasma model for the study of instabilities and turbulence in magnetised plasmas is presented, built on the BOUT++ framework. This cold ion model allows the evolution of global profiles, electric fields and flows on transport timescales, with flux-driven cross-field transport determined self-consistently by electromagnetic turbulence. Developments in the model formulation and numerical implementation are described, and simulations are performed in poloidally limited and diverted tokamak configurations.

  15. General Relativistic Simulations of Magnetized Plasmas around Merging Supermassive Black Holes

    CERN Document Server

    Giacomazzo, Bruno; Miller, M Coleman; Reynolds, Christopher S; van Meter, James R

    2012-01-01

    Coalescing supermassive black hole binaries are produced by the mergers of galaxies and are the most powerful sources of gravitational waves accessible to space-based gravitational observatories. Some such mergers may occur in the presence of matter and magnetic fields and hence generate an electromagnetic counterpart. In this paper we present the first general relativistic simulations of magnetized plasma around merging supermassive black holes using the general relativistic magnetohydrodynamic code Whisky. By considering different magnetic field strengths, going from non-magnetically dominated to magnetically dominated regimes, we explore how magnetic fields affect the dynamics of the plasma and the possible emission of electromagnetic signals. In particular we observe a total amplification of the magnetic field of ~2 orders of magnitude which is driven by the accretion onto the binary and that leads to much stronger electromagnetic signals, more than a factor of 10^4 larger than comparable calculations don...

  16. General Relativistic Simulations of Magnetized Plasmas around Merging Supermassive Black Holes

    Science.gov (United States)

    Giacomazzo, Bruno; Baker, John G.; Miller, M. Coleman; Reynolds, Christopher S.; van Meter, James R.

    2012-06-01

    Coalescing supermassive black hole binaries are produced by the mergers of galaxies and are the most powerful sources of gravitational waves accessible to space-based gravitational observatories. Some such mergers may occur in the presence of matter and magnetic fields and hence generate an electromagnetic counterpart. In this Letter, we present the first general relativistic simulations of magnetized plasma around merging supermassive black holes using the general relativistic magnetohydrodynamic code Whisky. By considering different magnetic field strengths, going from non-magnetically dominated to magnetically dominated regimes, we explore how magnetic fields affect the dynamics of the plasma and the possible emission of electromagnetic signals. In particular, we observe a total amplification of the magnetic field of ~2 orders of magnitude, which is driven by the accretion onto the binary and that leads to much stronger electromagnetic signals, more than a factor of 104 larger than comparable calculations done in the force-free regime where such amplifications are not possible.

  17. Effects of beam velocity and density on an ion-beam pulse moving in magnetized plasmas

    CERN Document Server

    Zhao, Xiao-ying; Zhao, Yong-tao; Qi, Xin; Yang, Lei

    2016-01-01

    The wakefield and stopping power of an ion-beam pulse moving in magnetized plasmas are investigated by particle-in-cell (PIC) simulations. The effects of beam velocity and density on the wake and stopping power are discussed. In the presence of magnetic field, it is found that beside the longitudinal conversed V-shaped wakes, the strong whistler wave are observed when low-density and low-velocity pulses moving in plasmas. The corresponding stopping powers are enhanced due to the drag of these whistler waves. As beam velocities increase, the whistler waves disappear, and only are conversed V-shape wakes observed. The corresponding stopping powers are reduced compared with these in isotropic plasmas. When high-density pulses transport in the magnetized plasmas, the whistler waves are greatly inhibited for low-velocity pulses and disappear for high-velocity pulses. Additionally, the magnetic field reduces the stopping powers for all high-density cases.

  18. Stimulated Brillouin scattering of an electromagnetic wave in weakly magnetized plasma with variably charged dust particles

    Indian Academy of Sciences (India)

    Sourabh Bal; M Bose

    2009-10-01

    We have investigated analytically the stimulated Brillouin scattering (SBS) of an electromagnetic wave in non-dissipative weakly magnetized plasma in the presence of dust particles with variable charge.

  19. Effect of structural steel ion plasma nitriding on material durability in pulsed high magnetic fields

    Science.gov (United States)

    Spirin, A. V.; Krutikov, V. I.; Koleukh, D. S.; Mamaev, A. S.; Paranin, S. N.; Gavrilov, N. V.; Kaigorodov, A. S.

    2017-05-01

    The work was aimed to study the influence of plasma nitriding on electrical and mechanical properties of structural steels and their durability in pulsed high magnetic field. The plates and cylindrical magnetic flux concentrators were made of several steel grades (30KhGS, 40Kh, 50KhGA, 38Kh2MYuA, and U8A), heat-treated, and subjected to the low-temperature (400, 500°C) plasma nitriding. Electrical and mechanical properties of materials, phase composition of steel surface layer, microstructure and microhardness profiles were investigated on the plates before and after plasma treatment. Microstructure and microhardness profiles across the subsurface layer of plasma treated and untreated concentrators applied for high magnetic field generation were also studied. Magnetic field of 50 T under tens of microseconds in duration inside the flux concentrators was generated by long-life outer coil.

  20. Influence of external resonant magnetic perturbation field on edge plasma of small tokamak HYBTOK-II

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Y., E-mail: hayashi-yuki13@ees.nagoya-u.ac.jp [Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Suzuki, Y.; Ohno, N. [Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Okamoto, M. [Ishikawa National College of Technology, Kitachujo, Tsubata-cho, Kahoku-gun, Ishikawa 929-0392 (Japan); Kikuchi, Y. [University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280 (Japan); Sakakibara, S.; Watanabe, K.; Takemura, Y. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292 (Japan)

    2015-08-15

    Radial profile of externally applied resonant magnetic perturbation (RMP) field with mode numbers of m = 6 and n = 2 in a small tokamak device HYBTOK-II have been investigated using a magnetic probe array, which is able to measure the radial profile of magnetic field perturbation induced by applying RMP. Results of RMP penetration into the plasma show that the RMP decreased toward the plasma center, while they were amplified around the resonant surface with a safety factor q = 3 due to the formation of magnetic islands. This suggests that RMP fields for controlling edge plasmas may trigger some kind of MHD instabilities. In addition, simulation results, based on a linearized four-field model, which agrees with the experimental ones, indicates that the penetration and amplification process of RMP strongly depend on a Doppler-shifted frequency between the RMP and plasma rotation.