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Sample records for anisotropic plasma heating

  1. Geodesic acoustic mode in anisotropic plasma with heat flux

    SciTech Connect

    Ren, Haijun

    2015-10-15

    Geodesic acoustic mode (GAM) in an anisotropic tokamak plasma is investigated in fluid approximation. The collisionless anisotropic plasma is described within the 16-momentum magnetohydrodynamic (MHD) fluid closure model, which takes into account not only the pressure anisotropy but also the anisotropic heat flux. It is shown that the GAM frequency agrees better with the kinetic result than the standard Chew-Goldberger-Low (CGL) MHD model. When zeroing the anisotropy, the 16-momentum result is identical with the kinetic one to the order of 1/q{sup 2}, while the CGL result agrees with the kinetic result only on the leading order. The discrepancies between the results of the CGL fluid model and the kinetic theory are well removed by considering the heat flux effect in the fluid approximation.

  2. Kinetic dissipation and anisotropic heating in a turbulent collisionless plasma

    SciTech Connect

    Parashar, T. N.; Shay, M. A.; Cassak, P. A.; Matthaeus, W. H.

    2009-03-15

    The kinetic evolution of the Orszag-Tang vortex is studied using collisionless hybrid simulations. In magnetohydrodynamics (MHD) this configuration leads rapidly to broadband turbulence. At large length scales, the evolution of the hybrid simulations is very similar to MHD, with magnetic power spectra displaying scaling similar to a Kolmogorov scaling of -5/3. At small scales, differences from MHD arise, as energy dissipates into heat almost exclusively through the magnetic field. The magnetic energy spectrum of the hybrid simulation shows a break where linear theory predicts that the Hall term in Ohm's law becomes significant, leading to dispersive kinetic Alfven waves. A key result is that protons are heated preferentially in the plane perpendicular to the mean magnetic field, creating a proton temperature anisotropy of the type observed in the corona and solar wind.

  3. Anisotropic electron-distribution function in inverse-bremsstrahlung-heated plasmas.

    PubMed

    Bendib, A; Bendib-Kalache, K; Cros, B; Maynard, G

    2016-04-01

    The electron-distribution function in homogeneous plasmas heated by a high-frequency laser field is calculated in velocity space from the Vlasov-Landau equation. The kinetic model is valid for moderate laser intensity defined by the relevant parameter α=v_{0}^{2}/v_{t}^{2}<0.5 where v_{0} and v_{t} are the peak velocity of oscillation in the high-frequency electric field and the thermal velocity, respectively. The results obtained constitute an improvement of the results reported in the literature devoted to weak electric field intensities. The electron-distribution function is calculated solving the kinetic equation with the use of the Legendre polynomial expansion within the laser field dipole approximation. It results in an infinite set of equations for the isotropic component f_{0}(v) and the anisotropic components f_{n≥1}(v) that we have solved numerically with appropriate truncation. For the second anisotropy f_{2}(v), we found that its maximum increases from the weak electric field intensity (α<0.01) to a moderate one (α=0.5) by a factor f_{2max}(α=0.5)/f_{2max}(α=0.01)≈48. Applications to the radiation pressure, electromagnetic instabilities, and photoabsorption are also considered. PMID:27176419

  4. Anisotropic electron-distribution function in inverse-bremsstrahlung-heated plasmas

    NASA Astrophysics Data System (ADS)

    Bendib, A.; Bendib-Kalache, K.; Cros, B.; Maynard, G.

    2016-04-01

    The electron-distribution function in homogeneous plasmas heated by a high-frequency laser field is calculated in velocity space from the Vlasov-Landau equation. The kinetic model is valid for moderate laser intensity defined by the relevant parameter α =v02/vt2<0.5 where v0 and vt are the peak velocity of oscillation in the high-frequency electric field and the thermal velocity, respectively. The results obtained constitute an improvement of the results reported in the literature devoted to weak electric field intensities. The electron-distribution function is calculated solving the kinetic equation with the use of the Legendre polynomial expansion within the laser field dipole approximation. It results in an infinite set of equations for the isotropic component f0(v ) and the anisotropic components fn ≥1(v ) that we have solved numerically with appropriate truncation. For the second anisotropy f2(v ) , we found that its maximum increases from the weak electric field intensity (α <0.01 ) to a moderate one (α =0.5 ) by a factor f2 max(α =0.5 ) / f2 max(α =0.01 ) ≈48 . Applications to the radiation pressure, electromagnetic instabilities, and photoabsorption are also considered.

  5. Modelling Coulomb Collisions in Anisotropic Plasmas

    NASA Astrophysics Data System (ADS)

    Hellinger, P.; Travnicek, P. M.

    2009-12-01

    Collisional transport in anisotropic plasmas is investigated comparing the theoretical transport coefficients (Hellinger and Travnicek, 2009) for anisotropic particles with the results of the corresponding Langevin equation, obtained as a generalization of Manheimer et al. (1997). References: Hellinger, P., and P. M. Travnicek (2009), On Coulomb collisions in bi-Maxwellian plasmas, Phys. Plasmas, 16, 054501. Manheimer, W. M., M. Lampe and G. Joyce (1997), Langevin representation of Coulomb collisions in PIC simulations, J. Comput. Phys., 138, 563-584.

  6. THE ANISOTROPIC TRANSPORT EFFECTS ON DILUTE PLASMAS

    SciTech Connect

    Devlen, Ebru

    2011-04-20

    We examine the linear stability analysis of a hot, dilute, and differentially rotating plasma by considering anisotropic transport effects. In dilute plasmas, the ion Larmor radius is small compared with its collisional mean free path. In this case, the transport of heat and momentum along the magnetic field lines becomes important. This paper presents a novel linear instability that may be more powerful and greater than ideal magnetothermal instability and ideal magnetorotational instability in the dilute astrophysical plasmas. This type of plasma is believed to be found in the intracluster medium (ICM) of galaxy clusters and radiatively ineffective accretion flows around black holes. We derive the dispersion relation of this instability and obtain the instability condition. There is at least one unstable mode that is independent of the temperature gradient direction for a helical magnetic field geometry. This novel instability is driven by the gyroviscosity coupled with differential rotation. Therefore, we call it gyroviscous-modified magnetorotational instability (GvMRI). We examine how the instability depends on signs of the temperature gradient and the gyroviscosity and also on the magnitude of the thermal frequency and on the values of the pitch angle. We provide a detailed physical interpretation of the obtained results. The GvMRI is applicable not only to the accretion flows and ICM but also to the transition region between cool dense gas and the hot low-density plasma in stellar coronae, accretion disks, and the multiphase interstellar medium because it is independent of the temperature gradient direction.

  7. Phonon heat conduction in layered anisotropic crystals

    NASA Astrophysics Data System (ADS)

    Minnich, A. J.

    2015-02-01

    The thermal properties of anisotropic crystals are of both fundamental and practical interest, but transport phenomena in anisotropic materials such as graphite remain poorly understood because solutions of the Boltzmann equation often assume isotropy. Here, we extend an analytic solution of the transient, frequency-dependent Boltzmann equation to highly anisotropic solids and examine its predictions for graphite. We show that this simple model predicts key results, such as long c -axis phonon mean free paths and a negative correlation of cross-plane thermal conductivity with in-plane group velocity, that were previously observed with computationally expensive molecular-dynamics simulations. Further, using our analytic solution, we demonstrate a method to reconstruct the anisotropic mean free path spectrum of crystals with arbitrary dispersion relations without any prior knowledge of their harmonic or anharmonic properties using observations of quasiballistic heat conduction. These results provide a useful analytic framework to understand thermal transport in anisotropic crystals.

  8. Transport equations for multicomponent anisotropic space plasmas - A review

    NASA Technical Reports Server (NTRS)

    Barakat, A. R.; Schunk, R. W.

    1982-01-01

    An attempt is made to present a unified approach to the study of transport phenomena in multicomponent anisotropic space plasmas. In particular, a system of generalized transport equations is presented that can be applied to widely different plasma flow conditions. The generalized transport equations can describe subsonic and supersonic flows, collision-dominated and collisionless flows, plasma flows in rapidly changing magnetic field configurations, multicomponent plasma flows with large temperature differences between the interacting species, and plasma flows that contain anisotropic temperature distributions. In addition, if Maxwell's equations of electricity and magnetism are added to the system of transport equations, they can be used to model electrostatic shocks, double layers, and magnetic merging processes. These transport equations also contain terms which act to regulate both the heat flow and temperature anisotropy, processes which appear to be operating in the solar wind.

  9. Ballooning stability of anisotropic, rotating plasmas

    NASA Technical Reports Server (NTRS)

    Wang, X.-H.; Bhattacharjee, A.

    1990-01-01

    The linearized equation of motion is given in a Lagrangian representation for a rotating plasma with anisotropic pressure. A WKB theory is developed for large-n ballooning modes in an axisymmetric configuration with field-aligned and rigid toroidal flows. In the presence of field-aligned flows, it is shown that a resonance occurs which is strongly suggestive of a generalized mirror instability. In the presence of toroidal rotation, a possible stabilizing effect is identified for P(normal) greater than P(parallel). Finally, as a special case of the theory, the necessary and sufficient conditions for stability in a static, anisotropic plasma are obtained.

  10. Local thermodynamics of a magnetized, anisotropic plasma

    SciTech Connect

    Hazeltine, R. D.; Mahajan, S. M.; Morrison, P. J.

    2013-02-15

    An expression for the internal energy of a fluid element in a weakly coupled, magnetized, anisotropic plasma is derived from first principles. The result is a function of entropy, particle density and magnetic field, and as such plays the role of a thermodynamic potential: it determines in principle all thermodynamic properties of the fluid element. In particular it provides equations of state for the magnetized plasma. The derivation uses familiar fluid equations, a few elements of kinetic theory, the MHD version of Faraday's law, and certain familiar stability and regularity conditions.

  11. Tokamak plasma equilibrium problems with anisotropic pressure and rotation and their numerical solution

    NASA Astrophysics Data System (ADS)

    Ivanov, A. A.; Martynov, A. A.; Medvedev, S. Yu.; Poshekhonov, Yu. Yu.

    2015-03-01

    In the MHD tokamak plasma theory, the plasma pressure is usually assumed to be isotropic. However, plasma heating by neutral beam injection and RF heating can lead to a strong anisotropy of plasma parameters and rotation of the plasma. The development of MHD equilibrium theory taking into account the plasma inertia and anisotropic pressure began a long time ago, but until now it has not been consistently applied in computational codes for engineering calculations of the plasma equilibrium and evolution in tokamak. This paper contains a detailed derivation of the axisymmetric plasma equilibrium equation in the most general form (with arbitrary rotation and anisotropic pressure) and description of the specialized version of the SPIDER code. The original method of calculation of the equilibrium with an anisotropic pressure and a prescribed rotational transform profile is proposed. Examples of calculations and discussion of the results are also presented.

  12. Tokamak plasma equilibrium problems with anisotropic pressure and rotation and their numerical solution

    SciTech Connect

    Ivanov, A. A. Martynov, A. A. Medvedev, S. Yu. Poshekhonov, Yu. Yu.

    2015-03-15

    In the MHD tokamak plasma theory, the plasma pressure is usually assumed to be isotropic. However, plasma heating by neutral beam injection and RF heating can lead to a strong anisotropy of plasma parameters and rotation of the plasma. The development of MHD equilibrium theory taking into account the plasma inertia and anisotropic pressure began a long time ago, but until now it has not been consistently applied in computational codes for engineering calculations of the plasma equilibrium and evolution in tokamak. This paper contains a detailed derivation of the axisymmetric plasma equilibrium equation in the most general form (with arbitrary rotation and anisotropic pressure) and description of the specialized version of the SPIDER code. The original method of calculation of the equilibrium with an anisotropic pressure and a prescribed rotational transform profile is proposed. Examples of calculations and discussion of the results are also presented.

  13. Effects of anisotropic heat conduction on solidification

    NASA Technical Reports Server (NTRS)

    Weaver, J. A.; Viskanta, R.

    1989-01-01

    Two-dimensional solidification influenced by anisotropic heat conduction has been considered. The interfacial energy balance was derived to account for the heat transfer in one direction (x or y) depending on the temperature gradient in both the x and y directions. A parametric study was made to determine the effects of the Stefan number, aspect ratio, initial superheat, and thermal conductivity ratios on the solidification rate. Because of the imposed boundary conditions, the interface became skewed and sometimes was not a straight line between the interface position at the upper and lower adiabatic walls (spatially nonlinear along the height). This skewness depends on the thermal conductivity ratio k(yy)/k(yx). The nonlinearity of the interface is influenced by the solidification rate, aspect ratio, and k(yy/k(yx).

  14. Current collection in an anisotropic collisionless plasma

    NASA Technical Reports Server (NTRS)

    Li, Wei-Wei

    1992-01-01

    A general method is given to derive the current-potential relations in anisotropic plasmas. Orbit limit current is assumed. The collector is a conductive sphere or an infinite cylinder. Any distribution which is an arbitrary function of the velocity vector can be considered as a superposition of many mono-energetic beams whose current-potential relations are known. The results for two typical pitch angle distributions are derived and discussed in detail. The general properties of the current potential relations are very similar to that of a Maxwellian plasma except for an effective temperature which varies with the angle between the magnetic field and the charging surface. The conclusions are meaningful to generalized geometries.

  15. Current collection in an anisotropic plasma

    NASA Technical Reports Server (NTRS)

    Li, Wei-Wei

    1990-01-01

    A general method is given to derive the current-potential relations in anisotropic plasmas. Orbit limit current is assumed. The collector is a conductive sphere or an infinite cylinder. Any distribution which is an arbitrary function of the velocity vector can be considered as a superposition of many mono-energetic beams whose current-potential relations are known. The results for two typical pitch angle distributions are derived and discussed in detail. The general properties of the current potential relations are very similar to that of a Maxwellian plasma except for an effective temperature which varies with the angle between the magnetic field and the charging surface. The conclusions are meaningful to generalized geometries.

  16. Quarkonium states in an anisotropic QCD plasma

    SciTech Connect

    Dumitru, Adrian; Guo Yun; Mocsy, Agnes; Strickland, Michael

    2009-03-01

    We consider quarkonium in a hot quantum chromodynamics (QCD) plasma which, due to expansion and nonzero viscosity, exhibits a local anisotropy in momentum space. At short distances the heavy-quark potential is known at tree level from the hard-thermal loop resummed gluon propagator in anisotropic perturbative QCD. The potential at long distances is modeled as a QCD string which is screened at the same scale as the Coulomb field. At asymptotic separation the potential energy is nonzero and inversely proportional to the temperature. We obtain numerical solutions of the three-dimensional Schroedinger equation for this potential. We find that quarkonium binding is stronger at nonvanishing viscosity and expansion rate, and that the anisotropy leads to polarization of the P-wave states.

  17. Renormalized anisotropic exchange for representing heat assisted magnetic recording media

    SciTech Connect

    Jiao, Yipeng; Liu, Zengyuan; Victora, R. H.

    2015-05-07

    Anisotropic exchange has been incorporated in a description of magnetic recording media near the Curie temperature, as would be found during heat assisted magnetic recording. The new parameters were found using a cost function that minimized the difference between atomistic properties and those of renormalized spin blocks. Interestingly, the anisotropic exchange description at 1.5 nm discretization yields very similar switching and magnetization behavior to that found at 1.2 nm (and below) discretization for the previous isotropic exchange. This suggests that the increased accuracy of anisotropic exchange may also reduce the computational cost during simulation.

  18. Nonlinear theory of slow dissipative layers in anisotropic plasmas

    SciTech Connect

    Ballai, I.; Ruderman, M.S.; Erdelyi, R.

    1998-01-01

    The solar coronal plasma is a well-known example of a plasma with strongly anisotropic dissipative coefficients. The main dissipative processes in the solar corona are strongly anisotropic thermal conductivity and viscosity. Ruderman and Goossens [Astrophys. J. {bold 471}, 1015 (1996)] developed a linear theory of driven slow resonant waves in plasmas with strongly anisotropic viscosity and thermal conductivity. Linear theory shows that in the slow dissipative layer the amplitudes of oscillations become very large for high Reynolds and Pecklet numbers, so that nonlinearity may be important. In the present paper the nonlinear behavior of driven magnetohydrodynamic waves in the slow dissipative layer in plasmas with strongly anisotropic viscosity and thermal conductivity is studied. The nonlinear governing equation for wave variables in the dissipative layer is derived. The nonlinear connection formulae, which are extensions of the linear connection formulae first introduced in the theory of resonant magnetohydrodynamic waves by Sakurai, Goossens, and Hollweg [Solar Phys. {bold 133}, 127 (1991)], are derived. {copyright} {ital 1998 American Institute of Physics.}

  19. Whistler Solitons in Plasma with Anisotropic Hot Electron Admixture

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Krivorutsky, E. N.; Gallagher, D. L.

    1999-01-01

    The longitudinal and transverse modulation instability of whistler waves in plasma, with a small admixture of hot anisotropic electrons, is discussed. If the hot particles temperature anisotropy is positive, it is found that, in such plasma, longitudinal perturbations can lead to soliton formation for frequencies forbidden in cold plasma. The soliton is enriched by hot particles. The frequency region unstable to transverse modulation in cold plasma in the presence of hot electrons is divided by stable domains. For both cases the role of hot electrons is more significant for whistlers with smaller frequencies.

  20. Probing strongly coupled anisotropic plasmas from higher curvature gravity

    NASA Astrophysics Data System (ADS)

    Jahnke, Viktor; Misobuchi, Anderson Seigo

    2016-06-01

    We consider five-dimensional AdS-axion-dilaton gravity with a Gauss-Bonnet term and use a black brane solution displaying spatial anisotropy as the gravity dual of a strongly coupled anisotropic plasma. We compute several observables relevant to the study of the plasma, namely, the drag force, the jet quenching parameter, the quarkonium potential, and the thermal photon production. The effects of higher derivative corrections and of the anisotropy are discussed and compared with previous results.

  1. NCSX Plasma Heating Methods

    SciTech Connect

    H.W. Kugel; D. Spong; R. Majeski; M. Zarnstorff

    2003-02-28

    The NCSX (National Compact Stellarator Experiment) has been designed to accommodate a variety of heating systems, including ohmic heating, neutral-beam injection, and radio-frequency. Neutral beams will provide one of the primary heating methods for NCSX. In addition to plasma heating, beams are also expected to provide a means for external control over the level of toroidal plasma rotation velocity and its profile. The plan is to provide 3 MW of 50 keV balanced neutral-beam tangential injection with pulse lengths of 500 msec for initial experiments, and to be upgradeable to pulse lengths of 1.5 sec. Subsequent upgrades will add 3 MW of neutral-beam injection. This Chapter discusses the NCSX neutral-beam injection requirements and design issues, and shows how these are provided by the candidate PBX-M (Princeton Beta Experiment-Modification) neutral-beam injection system. In addition, estimations are given for beam-heating efficiencies, scaling of heating efficiency with machine size an d magnetic field level, parameter studies of the optimum beam-injection tangency radius and toroidal injection location, and loss patterns of beam ions on the vacuum chamber wall to assist placement of wall armor and for minimizing the generation of impurities by the energetic beam ions. Finally, subsequent upgrades could add an additional 6 MW of radio-frequency heating by mode-conversion ion-Bernstein wave (MCIBW) heating, and if desired as possible future upgrades, the design also will accommodate high-harmonic fast-wave and electron-cyclotron heating. The initial MCIBW heating technique and the design of the radio-frequency system lend themselves to current drive, so that if current drive became desirable for any reason only minor modifications to the heating system described here would be needed. The radio-frequency system will also be capable of localized ion heating (bulk or tail), and possibly ion-Bernstein-wave-generated sheared flows.

  2. NCSX Plasma Heating Methods

    SciTech Connect

    Kugel, H. W.; Spong, D.; Majeski, R.; Zarnstorff, M.

    2008-01-18

    The National Compact Stellarator Experiment (NCSX) has been designed to accommodate a variety of heating systems, including ohmic heating, neutral beam injection, and radio-frequency (rf). Neutral beams will provide one of the primary heating methods for NCSX. In addition to plasma heating, neutral beams are also expected to provide a means for external control over the level of toroidal plasma rotation velocity and its profile. The experimental plan requires 3 MW of 50-keV balanced neutral beam tangential injection with pulse lengths of 500 ms for initial experiments, to be upgradeable to pulse lengths of 1.5 s. Subsequent upgrades will add 3MW of neutral beam injection (NBI). This paper discusses the NCSX NBI requirements and design issues and shows how these are provided by the candidate PBX-M NBI system. In addition, estimations are given for beam heating efficiencies, scaling of heating efficiency with machine size and magnetic field level, parameter studies of the optimum beam injection tangency radius and toroidal injection location, and loss patterns of beam ions on the vacuum chamber wall to assist placement of wall armor and for minimizing the generation of impurities by the energetic beam ions. Finally, subsequent upgrades could add an additional 6 MW of rf heating by mode conversion ion Bernstein wave (MCIBW) heating, and if desired as possible future upgrades, the design also will accommodate high-harmonic fast-wave and electron cyclotron heating. The initial MCIBW heating technique and the design of the rf system lend themselves to current drive, so if current drive became desirable for any reason, only minor modifications to the heating system described here would be needed. The rf system will also be capable of localized ion heating (bulk or tail), and possiblyIBW-generated sheared flows.

  3. Performance enhancement of IPMC by anisotropic plasma etching process

    NASA Astrophysics Data System (ADS)

    Lee, Seok Hwan; Kim, Chul-Jin; Hwang, Hyun-Woo; Kim, Sung-Joo; Yang, Hyun-Seok; Park, No-Cheol; Park, Young-Pil; Park, Kang-Ho; Lee, Hyung-Kun; Choi, Nak-Jin

    2009-03-01

    Ionic Polymer-Metal Composites (IPMCs) of EAP actuators is famous for its good property of response and durability. The performance of Ionic Polymer-Metal Composites (IPMCs) is an important issue which is affected by many factors. There are two factors for deciding the performance of IPMC. By treating anisotropic plasma etching process to 6 models of the IPMCs, enhanced experimental displacement and force results are obtained. Plasma patterning processes are executed by changing the groove and the land length of 6 patterns. The purpose of the present investigation is to find out the major factor which mainly affects the IPMC performance. Simulations using ANSYS have been executed to compare with the experimental results about the values and the tendency of data. Experimental and simulating data of the performances seem to have similar tendency. In the next part of the paper, we observed the other properties like capacitance, resistance and stiffness of 6 plasma patterned IPMCs. And we observed that the stiffness is the major factor which affects the performance of IPMCs. As we seen, our problem has been reduced to investigate about the property of stiffness. We suggest that the stiffness is largely changed mainly because of the different thickness of Platinum stacked of the groove and the land part which are produced by anisotropic plasma etching processes. And we understand that anisotropic plasma patterned IPMCs of better performance can be applied to various applications.

  4. A hybrid simulation study of magnetic reconnection in anisotropic plasmas

    NASA Astrophysics Data System (ADS)

    Guo, Jun; Li, Yi; Lu, Quan-ming; Wang, Shui

    2003-10-01

    The process of magnetic reconnection in anisotropic plasmas is studied numerically using a 2-dimensional, 3-component hybrid simulation. The results of the calculation show that, when the plasma pressure in the direction perpendicular to magnetic field is larger than that in the parallel direction (e.g. P ⊥/P ‖ = 1.5 ), instability may greatly increase, speeding up the rate of reconnection. When P⊥ is smaller than P‖, (e.g., when P ⊥/P ‖ = 0.6 ), fire hose instability appears, which will restrain the tearing mode instability and the process of magnetic reconnection.

  5. Analysis of stability of a homogeneous state of anisotropic plasma

    SciTech Connect

    Zakharov, V. Yu. Chernova, T. G. Stepanov, S. E.

    2015-04-15

    Small-amplitude waves in collisionless magnetized plasma are considered in the framework of one-fluid anisotropic magnetohydrodynamics with allowance for the anisotropy of the pressure and thermal flux. Stability of a homogeneous plasma state is analyzed using an eighth-order dispersion relation. Restrictions on the parameters of the homogeneous state at which the dispersion relation has no complex roots at any value of the angle between the wave vector and the unperturbed magnetic field are obtained. The applied method also makes it possible to determine the types of unstable waves.

  6. On the drift magnetosonic waves in anisotropic low beta plasmas

    SciTech Connect

    Naim, Hafsa; Bashir, M. F.; Murtaza, G.

    2014-10-15

    A generalized dispersion relation of obliquely propagating drift magnetosonic waves is derived by using the gyrokinetic theory for anisotropic low beta plasmas. The stability analysis applicable to a wide range of plasma parameters is performed to understand the stabilization mechanism of the drift magnetosonic instability and the estimation of the growth rate is also presented. It is noted that the growth rate of the drift instability enhances for small anisotropy (A{sub e,i} = T{sub ⊥e,i}/T{sub ∥e,i} < 1) whereas it is suppressed for large anisotropy (A{sub e,i} > 1)

  7. Adiabatically reduced magnetohydrodynamic equations for a cylindrical plasma with an anisotropic pressure

    SciTech Connect

    Nebogatov, V. A.; Pastukhov, V. P.

    2013-06-15

    A closed set of reduced equations describing low-frequency nonlinear flute magnetohydrodynamic (MHD) convection and the resulting nondiffusive processes of particle and energy transport in a weakly collisional cylindrical plasma with an anisotropic pressure is derived. The Chew-Goldberger-Low anisotropic magnetohydrodynamics is used as the basic dynamic model, because this model is applicable to describing flute convection in a cylindrical plasma column even in the low-frequency limit. The reduced set of equations was derived using the method of adiabatic separation of fast and slow motions. It is shown that the structure of the adiabatic transformation and the corresponding velocity field are identical to those obtained earlier in the isotropic MHD model. However, the derived heat transfer equations differ drastically from the isotropic pressure model. In particular, they indicate a tendency toward maintaining different radial profiles of the longitudinal and transverse pressures.

  8. Radiative heat transport instability in a laser produced inhomogeneous plasma

    SciTech Connect

    Bychenkov, V. Yu.; Rozmus, W.

    2015-08-15

    A laser produced high-Z plasma in which an energy balance is achieved due to radiation emission and radiative heat transfer supports ion acoustic instability. A linear dispersion relation is derived, and instability is compared to the radiation cooling instability [R. G. Evans, Plasma Phys. Controlled Fusion 27, 751 (1985)]. Under conditions of indirect drive fusion experiments, the driving term for the instability is the radiative heat flux and, in particular, the density dependence of the radiative heat conductivity. A specific example of thermal Bremsstrahlung radiation source has been considered. This instability may lead to plasma jet formation and anisotropic x-ray generation, thus affecting inertial confinement fusion related experiments.

  9. Wave instabilities in an anisotropic magnetized space plasma

    NASA Astrophysics Data System (ADS)

    Dzhalilov, N. S.; Kuznetsov, V. D.; Staude, J.

    2008-10-01

    Aims: We study wave instability in an collisionless, rarefied hot plasma (e.g. solar wind or corona). We consider the anisotropy produced by the magnetic field, when the thermal gas pressures across and along the field become unequal. Methods: We apply the 16-moment transport equations (obtained from the Boltzmann-Vlasov kinetic equation) including the anisotropic thermal fluxes. The general dispersion relation for the incompressible wave modes is derived. Results: It is shown that a new, more complex wave spectrum with stable and unstable behavior is possible, in contrast to the classic fire-hose modes obtained in terms of the 13-moment integrated equations.

  10. Analytical modeling of equilibrium of strongly anisotropic plasma in tokamaks and stellarators

    SciTech Connect

    Lepikhin, N. D.; Pustovitov, V. D.

    2013-08-15

    Theoretical analysis of equilibrium of anisotropic plasma in tokamaks and stellarators is presented. The anisotropy is assumed strong, which includes the cases with essentially nonuniform distributions of plasma pressure on magnetic surfaces. Such distributions can arise at neutral beam injection or at ion cyclotron resonance heating. Then the known generalizations of the standard theory of plasma equilibrium that treat p{sub ‖} and p{sub ⊥} (parallel and perpendicular plasma pressures) as almost constant on magnetic surfaces are not applicable anymore. Explicit analytical prescriptions of the profiles of p{sub ‖} and p{sub ⊥} are proposed that allow modeling of the anisotropic plasma equilibrium even with large ratios of p{sub ‖}/p{sub ⊥} or p{sub ⊥}/p{sub ‖}. A method for deriving the equation for the Shafranov shift is proposed that does not require introduction of the flux coordinates and calculation of the metric tensor. It is shown that for p{sub ⊥} with nonuniformity described by a single poloidal harmonic, the equation for the Shafranov shift coincides with a known one derived earlier for almost constant p{sub ⊥} on a magnetic surface. This does not happen in the other more complex case.

  11. Heat kernel for flat generalized Laplacians with anisotropic scaling

    NASA Astrophysics Data System (ADS)

    Mamiya, A.; Pinzul, A.

    2014-06-01

    We calculate the closed analytic form of the solution of heat kernel equation for the anisotropic generalizations of flat Laplacian. We consider a UV as well as UV/IR interpolating generalizations. In all cases, the result can be expressed in terms of Fox-Wright psi-functions. We perform different consistency checks, analytically reproducing some of the previous numerical or qualitative results, such as spectral dimension flow. Our study should be considered as a first step towards the construction of a heat kernel for curved Hořava-Lifshitz geometries, which is an essential ingredient in the spectral action approach to the construction of the Hořava-Lifshitz gravity.

  12. Bulk viscosity of anisotropically expanding hot QCD plasma

    SciTech Connect

    Chandra, Vinod

    2011-11-01

    The bulk viscosity, {zeta} and its ratio with the shear viscosity, {zeta}/{eta} have been studied in an anisotropically expanding pure glue plasma in the presence of turbulent color fields. It has been shown that the anisotropy in the momentum distribution function of gluons, which has been determined from a linearized transport equation eventually leads to the bulk viscosity. For the isotropic (equilibrium) state, a recently proposed quasiparticle model of pure SU(3) lattice QCD equation of state has been employed where the interactions are encoded in the effective fugacity. It has been argued that the interactions present in the equation of state, significantly contribute to the bulk viscosity. Its ratio with the shear viscosity is significant even at 1.5T{sub c}. Thus, one needs to take in account the effects of the bulk viscosity while studying the hydrodynamic expansion of quark-gluon plasma in the Relativistic Heavy Ion Collider and the Large Hadron Collider.

  13. Plasma heat pump and heat engine

    SciTech Connect

    Avinash, K.

    2010-08-15

    A model system where cold charged particles are locally confined in a volume V{sub P} within a warm plasma of volume V (V{sub P}<plasma heat and vice versa. Two applications of this theory are, first we propose a pumping device which heats plasmas by an adiabatic/isothermal compression of fields. Heating power ranging from a few hundred watts to a few kilowatts is possible with the present day technology. Second, we discuss the feasibility of constructing an electrostatic heat engine which converts plasma heat into mechanical work via plasma electric fields. Effects of P{sub E} are shown to be observable in colloidal solutions.

  14. Radiative heat transfer in anisotropic many-body systems: Tuning and enhancement

    SciTech Connect

    Nikbakht, Moladad

    2014-09-07

    A general formalism for calculating the radiative heat transfer in many body systems with anisotropic component is presented. Our scheme extends the theory of radiative heat transfer in isotropic many body systems to anisotropic cases. In addition, the radiative heating of the particles by the thermal bath is taken into account in our formula. It is shown that the radiative heat exchange (HE) between anisotropic particles and their radiative cooling/heating (RCH) could be enhanced several order of magnitude than that of isotropic particles. Furthermore, we demonstrate that both the HE and RCH can be tuned dramatically by particles relative orientation in many body systems.

  15. Plasma Heating: An Advanced Technology

    NASA Technical Reports Server (NTRS)

    1994-01-01

    The Mercury and Apollo spacecraft shields were designed to protect astronauts from high friction temperatures (well over 2,000 degrees Fahrenheit) when re-entering the Earth's atmosphere. It was necessary to test and verify the heat shield materials on Earth before space flight. After exhaustive research and testing, NASA decided to use plasma heating as a heat source. This technique involves passing a strong electric current through a rarefied gas to create a plasma (ionized gas) that produces an intensely hot flame. Although NASA did not invent the concept, its work expanded the market for commercial plasma heating systems. One company, Plasma Technology Corporation (PTC), was founded by a member of the team that developed the Re-entry Heating Simulator at Ames Research Center (ARC). Dr. Camacho, President of PTC, believes the technology has significant environmental applications. These include toxic waste disposal, hydrocarbon, decomposition, medical waste disposal, asbestos waste destruction, and chemical and radioactive waste disposal.

  16. Radiative heat transport instability in ICF plasmas

    NASA Astrophysics Data System (ADS)

    Rozmus, W.; Bychenkov, V. Yu.

    2015-11-01

    A laser produced high-Z plasma in which an energy balance is achieved due to radiation losses and radiative heat transfer supports ion acoustic wave instability. A linear dispersion relation is derived and instability is compared to the radiation cooling instability. This instability develops in the wide range of angles and wavenumbers with the typical growth rate on the order of cs/LT (cs is the sound speed, LT is the temperature scale length). In addition to radiation dominated systems, a similar thermal transport driven ion acoustic instability was found before in plasmas where the thermal transport coefficient depends on electron density. However, under conditions of indirect drive ICF experiments the driving term for the instability is the radiative heat flux and in particular, the density dependence of the radiative heat conductivity. A specific example of thermal Bremsstrahlung radiation source has been considered corresponding to a thermal conductivity coefficient that is inversely proportional to the square of local particle density. In the nonlinear regime this instability may lead to plasma jet formation and anisotropic x-ray generation.

  17. Anisotropic confinement effects in a two-dimensional plasma crystal.

    PubMed

    Laut, I; Zhdanov, S K; Räth, C; Thomas, H M; Morfill, G E

    2016-01-01

    The spectral asymmetry of the wave-energy distribution of dust particles during mode-coupling-induced melting, observed for the first time in plasma crystals by Couëdel et al. [Phys. Rev. E 89, 053108 (2014)PLEEE81539-375510.1103/PhysRevE.89.053108], is studied theoretically and by molecular-dynamics simulations. It is shown that an anisotropy of the well confining the microparticles selects the directions of preferred particle motion. The observed differences in intensity of waves of opposed directions are explained by a nonvanishing phonon flux. Anisotropic phonon scattering by defects and Umklapp scattering are proposed as possible reasons for the mean phonon flux. PMID:26871180

  18. Turbulent anomalous transport and anisotropic electron heating in a return current system

    SciTech Connect

    Lee, Kuang Wu; Buechner, Joerg

    2011-02-15

    Anisotropic electron heating due to self-generated electromagnetic turbulences is observed in collisionless return current plasmas. The corresponding energy conversion, electron heating, and associated anomalous momentum transport are investigated by means of a two-dimensional electromagnetic particle-in-cell simulation code. The return current model consists of two counterstreaming electron beams with different temperatures and a stationary ion background. First, a general multifluid dispersion analyzer is presented in a clear matrix form that allows to study electron streaming instabilities. The numerical simulation confirms the predicted electrostatic electron-electron acoustic instability. Generating electromagnetic waves, the system evolves into a nonlinear stage. As a result, the electron drifts are slowed down due to turbulence-induced anomalous momentum exchange. Localized electric and magnetic field fluctuations play major roles in the energy conversion. Perpendicular electron heating follows the growth of magnetic field perturbations and the slowing of the electron drifts. Parallel and perpendicular electron heating occurs at different time scales. It is shown that the longer lasting perpendicular electron heating is caused by preheated parallel electron flows. The deflection of the preheated parallel electron flows in the localized turbulences, which is essentially a two-dimensional effect, leads to perpendicular electron heating even after the saturation of parallel electron heating. We conclude that the self-generated magnetic turbulence dominates the anomalous transport process in the late stage of return current system evolution.

  19. Observations of Anisotropic Ion Temperature during RF Heating in the NSTX Edge

    SciTech Connect

    T.M. Biewer; R.E. Bell; D.S. Darrow; C.K. Phillips; J.R. Wilson

    2003-05-19

    A new spectroscopic diagnostic on the National Spherical Torus Experiment (NSTX) measures the velocity distribution of ions in the plasma edge with both poloidal and toroidal views. An anisotropic ion temperature is measured during the presence of high power HHFW RF heating in He plasmas, with the poloidal T(sub)i roughly twice the toroidal T(sub)i. Moreover, the measured spectral distribution suggests that two populations have temperatures of 500 eV and 50 eV with rotation velocities of -50 km/s and -10 km/s, respectively. This bi-modal distribution is observed in both the toroidal and poloidal views (in both He II and C III ions), and is well correlated with the period of RF power application to the plasma. The temperature of the edge ions is observed to increase with the applied RF power, which was scanned between 0 and 4.3MW. The ion heating mechanism from HHFW RF power has not yet been identified.

  20. Perpendicular ion heating by anisotropic whistler turbulence at electron scales

    NASA Astrophysics Data System (ADS)

    Saito, S.; Nariyuki, Y.

    2013-12-01

    Magnetic energy spectrum in the solar wind turbulence is observed in very broad scale range, extending from Magnetohydrodynamic (MHD) scales to electron scales. The frequency spectrum observed at a position of spacecraft has a power-law feature, but its index is different depending on the frequency range. In low frequencies (< 0.1Hz) corresponding to the MHD scales in the solar wind at 1AU, where the Taylor hypothesis (scale size = solar wind speed / observed frequency) is assumed, the power-law index -5/3 is typically observed. This scale range is referred to as the inertial range. At higher frequencies, which correspond to the shorter scales, the power-law spectrum tends to be steeper than the inertial range. The steeper spectrum is considered to be due to the dissipation and/or dispersion effect of kinetic-wave turbulence. Many authors have discussed nonlinear properties and dissipation processes of the kinetic-wave turbulence at the ion and electron scales in theory, simulation, and observation. By using particle-in-cell simulation that includes kinetic effects of both ions and electrons, we study the ion heating by anisotropic whistler turbulence at electron scales that is of the order of electron inertial length. Whistler turbulence cascades their fluctuation energy in wavenumber space more preferentially to the perpendicular direction to the background magnetic field than parallel. The highly obliquely propagating whistler waves have electric fluctuations at wavenumbers perpendicular to the background magnetic field. By interacting with the perpendicular electric fluctuations, the ions are stochastically scattered into the perpendicular direction. Our simulation results show that whistler turbulence can transfer their fluctuation energy into not only electrons but also the perpendicular energy of ions. It suggests that whistler turbulence even at the electron scales contributes the perpendicular heating of protons in the solar wind. Whistler turbulence could

  1. Nuclear modification factor in an anisotropic quark-gluon plasma

    NASA Astrophysics Data System (ADS)

    Mandal, Mahatsab; Bhattacharya, Lusaka; Roy, Pradip

    2011-10-01

    We calculate the nuclear modification factor (RAA) of light hadrons by taking into account the initial state momentum anisotropy of the quark-gluon plasma (QGP) expected to be formed in relativistic heavy ion collisions. Such an anisotropy can result from the initial rapid longitudinal expansion of the matter. A phenomenological model for the space-time evolution of the anisotropic QGP is used to obtain the time dependence of the anisotropy parameter ξ and the hard momentum scale, phard. The result is then compared with the PHENIX experimental data to constrain the isotropization time scale, τiso for fixed initial conditions (FIC). It is shown that the extracted value of τiso lies in the range 0.5⩽τiso⩽1.5. However, using a fixed final multiplicity (FFM) condition does not lead to any firm conclusion about the extraction of the isotropization time. The present calculation is also extended to contrast with the recent measurement of nuclear modification factor by the ALICE collaboration at s=2.76 TeV. It is argued that in the present approach, the extraction of τiso at this energy is uncertain and, therefore, refinement of the model is necessary. The sensitivity of the results on the initial conditions has been discussed. We also present the nuclear modification factor at Large Hadron Collider (LHC) energies with s=5.5 TeV.

  2. Alfven waves in dusty plasmas with plasma particles described by anisotropic kappa distributions

    SciTech Connect

    Galvao, R. A.; Ziebell, L. F.; Gaelzer, R.; Juli, M. C. de

    2012-12-15

    We utilize a kinetic description to study the dispersion relation of Alfven waves propagating parallelly to the ambient magnetic field in a dusty plasma, taking into account the fluctuation of the charge of the dust particles, which is due to inelastic collisions with electrons and ions. We consider a plasma in which the velocity distribution functions of the plasma particles are modelled as anisotropic kappa distributions, study the dispersion relation for several combinations of the parameters {kappa}{sub Parallel-To} and {kappa}{sub Up-Tack }, and emphasize the effect of the anisotropy of the distributions on the mode coupling which occurs in a dusty plasma, between waves in the branch of circularly polarized waves and waves in the whistler branch.

  3. PLASMA HEATING AND CONFINING DEVICE

    DOEpatents

    Baker, W.R.; Bratenahl, Al.; Kunkel, W.B.

    1962-02-13

    ABS> A device is designed for generating, heating, and containing a very pure electrical plasma. Plasma purity is maintained by preventing the hot plasma from contacting insulators, which are a principal source of impurities in prior constructions. An insulator is disposed at each end of a pair of long coaxial cylinders forming an annular chamber therebetween. High voltage is applied between the cylinders and an axial magnetic field is created therethrough. At a middle position on the inner cylinder, a fastopening valve releases a quantity of gas into the chamber, and before the gas can diffuse to the distant insulators, a discharge occurs between the cylinders and plasma is formed in the central region of the chamber away from the insulators. (AEC)

  4. Ion-cyclotron instability in current-carrying Lorentzian (kappa) and Maxwellian plasmas with anisotropic temperatures: A comparative study

    SciTech Connect

    Basu, B.; Grossbard, N. J.

    2011-09-15

    Current-driven electrostatic ion-cyclotron instability has so far been studied for Maxwellian plasma with isotropic and anisotropic temperatures. Since satellite-measured particle velocity distributions in space are often better modeled by the generalized Lorentzian (kappa) distributions and since temperature anisotropy is quite common in space plasmas, theoretical analysis of the current-driven, electrostatic ion-cyclotron instability is carried out in this paper for electron-proton plasma with anisotropic temperatures, where the particle parallel velocity distributions are modeled by kappa distributions and the perpendicular velocity distributions are modeled by Maxwellian distributions. Stability properties of the excited ion cyclotron modes and, in particular, their dependence on electron to ion temperature ratio and ion temperature anisotropy are presented in more detail. For comparison, the corresponding results for bi-Maxwellian plasma are also presented. Although the stability properties of the ion cyclotron modes in the two types of plasmas are qualitatively similar, significant quantitative differences can arise depending on the values of {kappa}{sub e} and {kappa}{sub i}. The comparative study is based on the numerical solutions of the respective linear dispersion relations. Quasilinear estimates of the resonant ion heating rates due to ion-cyclotron turbulence in the two types of plasma are also presented for comparison.

  5. Understanding anisotropic plasma etching of two-dimensional polystyrene opals for advanced materials fabrication.

    PubMed

    Akinoglu, Eser M; Morfa, Anthony J; Giersig, Michael

    2014-10-21

    Anisotropic deformation of polystyrene particles in an oxygenated (O2/Ar) plasma is observed for radio frequency (rf) plasma and inductively coupled plasma (ICP). A facile model based on a ratio of completely isotropic and completely anisotropic etching is presented to describe the anisotropy of the etching process and is implemented to determine the height of the spheroid-shaped polystyrene particles. In our systems, we find the plasma etching to be 54% isotropic in the rf plasma and 79% isotropic in the ICP. With this model, the maximum material deposition thickness for nanofabrication with plasma-etched nanosphere lithography or colloid lithography can be predicted. Moreover, the etching of polystyrene particles in an oxygenated plasma is investigated versus the etching time, gas flow, gas composition, temperature, substrate material, and particle size. The results of this study allow precise shape tuning during the fabrication of nanostructured surfaces with size-dependent properties for bionic, medical, and photonic applications. PMID:24580644

  6. An implicit scheme for solving the anisotropic diffusion of heat and cosmic rays in the RAMSES code

    NASA Astrophysics Data System (ADS)

    Dubois, Yohan; Commerçon, Benoît

    2016-01-01

    Astrophysical plasmas are subject to a tight connection between magnetic fields and the diffusion of particles, which leads to an anisotropic transport of energy. Under the fluid assumption, this effect can be reduced to an advection-diffusion equation, thereby augmenting the equations of magnetohydrodynamics. We introduce a new method for solving the anisotropic diffusion equation using an implicit finite-volume method with adaptive mesh refinement and adaptive time-stepping in the ramses code. We apply this numerical solver to the diffusion of cosmic ray energy and diffusion of heat carried by electrons, which couple to the ion temperature. We test this new implementation against several numerical experiments and apply it to a simple supernova explosion with a uniform magnetic field.

  7. Plasma heating of Io's atmosphere

    NASA Technical Reports Server (NTRS)

    Pospieszalska, M. K.; Johnson, R. E.

    1992-01-01

    A Monte-Carlo, molecule-tracking program was constructed to describe the structure of Io's atmosphere in the region penetrated by ions from the plasma torus. This region is shown to exhibit high temperatures, consistent with corona observations, independent of whether significant UV heating also occurs. The atmospheric structure is determined near the exobase, which is the region responsible for the supply of the Io torus.

  8. Anisotropic heat transport in reversed shear configurations: shearless Cantori barriers and nonlocal transport

    NASA Astrophysics Data System (ADS)

    Blasevski, D.; Del-Castillo-Negrete, D.

    2012-10-01

    Heat transport in magnetized plasmas is a problem of fundamental interest in controlled fusion. In Ref.footnotetext D. del-Castillo-Negrete, and L. Chac'on, Phys. Rev. Lett., 106, 195004 (2011); Phys. Plasmas 19, 056112 (2012). we proposed a Lagrangian-Green's function (LG) method to study this problem in the strongly anisotropic (χ=0) regime. The LG method bypasses the need to discretize the transport operators on a grid and it is applicable to general parallel flux closures and 3-D magnetic fields. Here we apply the LG method to parallel transport (with local and nonlocal parallel flux closures) in reversed shear magnetic field configurations known to exhibit robust transport barriers in the vicinity of the extrema of the q-profile. By shearless Cantori (SC) we mean the invariant Cantor sets remaining after the destruction of toroidal flux surfaces with zero magnetic shear, q^'=0. We provide numerical evidence of the role of SC in the anomalously slow relaxation of radial temperature gradients in chaotic magnetic fields with no transport barriers. The spatio-temporal evolution of temperature pulses localized in the reversed shear region exhibits non-diffusive self-similar evolution and nonlocal effective radial transport.

  9. Quark-gluon plasma phenomenology from anisotropic lattice QCD

    NASA Astrophysics Data System (ADS)

    Skullerud, Jon-Ivar; Aarts, Gert; Allton, Chris; Amato, Alessandro; Burnier, Yannis; Evans, P. Wynne M.; Giudice, Pietro; Hands, Simon; Harris, Tim; Kelly, Aoife; Kim, Seyong; Lombardo, Maria Paola; Oktay, Mehmet B.; Rothkopf, Alexander; Ryan, Sinéad M.

    2016-01-01

    The FASTSUM collaboration has been carrying out simulations of Nf = 2 + 1 QCD at nonzero temperature in the fixed-scale approach using anisotropic lattices. Here we present the status of these studies, including recent results for electrical conductivity and charge diffusion, and heavy quarkonium (charm and beauty) physics.

  10. Multi-band near-field radiative heat transfer between two anisotropic fishnet metamaterials

    NASA Astrophysics Data System (ADS)

    Bai, Yang; Jiang, Yongyuan; Liu, Linhua

    2015-06-01

    We study the near-field radiative heat transfer between two metal-insulator-metal sandwiched-like fishnet metamaterials (FMMs) by fluctuation electrodynamics. Results show that multi-band heat flux between the fishnet metamaterials is achieved, which is attributed to the thermally excited surface modes within the FMM. Apart from the electric response mode of the near-field heat flux, magnetic modes are also existed, which are related with the excitations of the surface plasmon polaritons (SPPs) propagating on the outer surface of metal (external SPPs) and along the inner metal-dielectric interface (internal SPPs). Moreover, we show that the electromagnetic parameters of this anisotropic fishnet metamaterial depend on the angles θ of the incident light when heating the fishnet metamaterial, and thus the overall effect of the anisotropic FMM parameters is considered to predict the near-field radiative heat transfer. Different external-SPPs and internal-SPPs modes are excited at different frequencies which is attributed to the anisotropic electromagnetic response of FMM, which open new frequency channels of the near-field radiative heat transfer. This kind of anisotropic metamaterial should assist in thermal management in nanoscale.

  11. Propagation of Polarized Cosmic Microwave Background Radiation in an Anisotropic Magnetized Plasma

    SciTech Connect

    Moskaliuk, S. S.

    2010-01-01

    The polarization plane of the cosmic microwave background radiation (CMBR) can be rotated either in a space-time with metric of anisotropic type and in a magnetized plasma or in the presence of a quintessential background with pseudoscalar coupling to electromagnetism. A unified treatment of these three phenomena is presented for cold anisotropic plasma at the pre-recombination epoch. It is argued that the generalized expressions derived in the present study may be relevant for direct searches of a possible rotation of the cosmic microwave background polarization.

  12. Relativistic and non-relativistic analysis of whistler-mode waves in a hot anisotropic plasma

    NASA Astrophysics Data System (ADS)

    Sazhin, S. S.; Sumner, A. E.; Temme, N. M.

    1992-02-01

    The dispersion equation for parallel whistler-mode propagation in a hot anisotropic plasma is analysed numerically in both weakly relativistic and nonrelativistic approximations under the assumption that wave growth or damping does not influence the wave refractive index. The results of this analysis are compared with the results of an asymptotic analysis of the same equation, and the range of applicability of the latter results is specified. It is pointed out that relativistic effects lead to a decrease in the range of frequencies for which instability occurs. For a moderately anisotropic plasma (T/T = 2) relativistic effects lead to an increase in the maximum value of the increment of instability.

  13. The residual zonal flows in anisotropic tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Ren, Haijun

    2016-06-01

    The gyro-kinetic equation is analytically solved based on the anisotropic two-temperature distribution, in which the ions' parallel temperature is a flux function while the perpendicular temperature depends on the poloidal angle. The residual level of collisionless zonal flows (ZFs) is derived and calculated in the large aspect circular limit. Our result shows that the anisotropy plays a remarkable role in determining the residual value of ZFs. Even weak anisotropy can significantly change the residual level.

  14. Resonant-cavity antenna for plasma heating

    DOEpatents

    Perkins, F.W. Jr.; Chiu, S.C.; Parks, P.; Rawls, J.M.

    1984-01-10

    This invention relates generally to a method and apparatus for transferring energy to a plasma immersed in a magnetic field, and relates particularly to an apparatus for heating a plasma of low atomic number ions to high temperatures by transfer of energy to plasma resonances, particularly the fundamental and harmonics of the ion cyclotron frequency of the plasma ions. This invention transfers energy from an oscillating radio-frequency field to a plasma resonance of a plasma immersed in a magnetic field.

  15. An asymptotic-preserving Lagrangian algorithm for the time-dependent anisotropic heat transport equation

    SciTech Connect

    Chacon, Luis; del-Castillo-Negrete, Diego; Hauck, Cory D.

    2014-09-01

    We propose a Lagrangian numerical algorithm for a time-dependent, anisotropic temperature transport equation in magnetized plasmas in the large guide field regime. The approach is based on an analytical integral formal solution of the parallel (i.e., along the magnetic field) transport equation with sources, and it is able to accommodate both local and non-local parallel heat flux closures. The numerical implementation is based on an operator-split formulation, with two straightforward steps: a perpendicular transport step (including sources), and a Lagrangian (field-line integral) parallel transport step. Algorithmically, the first step is amenable to the use of modern iterative methods, while the second step has a fixed cost per degree of freedom (and is therefore scalable). Accuracy-wise, the approach is free from the numerical pollution introduced by the discrete parallel transport term when the perpendicular to parallel transport coefficient ratio X /X becomes arbitrarily small, and is shown to capture the correct limiting solution when ε = X⊥L2/X1L2 → 0 (with L∥∙ L⊥ , the parallel and perpendicular diffusion length scales, respectively). Therefore, the approach is asymptotic-preserving. We demonstrate the capabilities of the scheme with several numerical experiments with varying magnetic field complexity in two dimensions, including the case of transport across a magnetic island.

  16. Modeling anisotropic flow and heat transport by using mimetic finite differences

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Clauser, Christoph; Marquart, Gabriele; Willbrand, Karen; Büsing, Henrik

    2016-08-01

    Modeling anisotropic flow in porous or fractured rock often assumes that the permeability tensor is diagonal, which means that its principle directions are always aligned with the coordinate axes. However, the permeability of a heterogeneous anisotropic medium usually is a full tensor. For overcoming this shortcoming, we use the mimetic finite difference method (mFD) for discretizing the flow equation in a hydrothermal reservoir simulation code, SHEMAT-Suite, which couples this equation with the heat transport equation. We verify SHEMAT-Suite-mFD against analytical solutions of pumping tests, using both diagonal and full permeability tensors. We compare results from three benchmarks for testing the capability of SHEMAT-Suite-mFD to handle anisotropic flow in porous and fractured media. The benchmarks include coupled flow and heat transport problems, three-dimensional problems and flow through a fractured porous medium with full equivalent permeability tensor. It shows firstly that the mimetic finite difference method can model anisotropic flow both in porous and in fractured media accurately and its results are better than those obtained by the multi-point flux approximation method in highly anisotropic models, secondly that the asymmetric permeability tensor can be included and leads to improved results compared the symmetric permeability tensor in the equivalent fracture models, and thirdly that the method can be easily implemented in existing finite volume or finite difference codes, which has been demonstrated successfully for SHEMAT-Suite.

  17. Instabilities of collisionless current sheets revisited: The role of anisotropic heating

    SciTech Connect

    Muñoz, P. A. Kilian, P. Büchner, J.

    2014-11-15

    In this work, we investigate the influence of the anisotropic heating on the spontaneous instability and evolution of thin Harris-type collisionless current sheets, embedded in antiparallel magnetic fields. In particular, we explore the influence of the macroparticle shape-function using a 2D version of the PIC code ACRONYM. We also investigate the role of the numerical collisionality due to the finite number of macroparticles in PIC codes. It is shown that it is appropriate to choose higher order shape functions of the macroparticles compared to a larger number of macroparticles per cell. This allows to estimate better the anisotropic electron heating due to the collisions of macroparticles in a PIC code. Temperature anisotropies can stabilize the tearing mode instability and trigger additional current sheet instabilities. We found a good agreement between the analytically derived threshold for the stabilization of the anisotropic tearing mode and other instabilities, either spontaneously developing or initially triggered ones. Numerical effects causing anisotropic heating at electron time scales become especially important for higher mass ratios (above m{sub i}/m{sub e}=180). If numerical effects are carefully taken into account, one can recover the theoretical estimated linear growth rates of the tearing instability of thin isotropic collisionless current sheets, also for higher mass ratios.

  18. RF plasma heating in toroidal fusion devices

    SciTech Connect

    Golant, V.E.; Fedorov, V.I. )

    1989-01-01

    The purpose of the present book is to provide, in seven chapters, a unified overview of the methods for rf heating of plasmas in toroidal fusion experiments. In Chapter 1 the problem of plasma heating in tokamaks and stellarators is formulated and the requirements for auxiliary heating techniques are described. This chapter also contains a brief review of the results of research on tokamaks and stellarators. Chapter 2 is devoted to a theoretical description of the principal physical effects involved in the rf heating of plasmas, especially the characteristics of wave propagation, of the mechanisms by which waves are absorbed and plasma heating takes place, and of the nonlinear effects that accompany heating. The primary emphasis is on a qualitative physical picture of these effects. Chapters 3-6, in turn, deal with the major rf heating techniques currently under investigation, electron cyclotron (ECH), ion cyclotron (ICH), lower hybrid (LHH), and Alfven wave heating. In each of these chapters the main schemes for heating are described, the results of theoretical analyses and numerical simulations are discussed, the technology of the heating systems is briefly described, and experimental work published through the end of 1984 is reviewed. Finally, in Chapter 7 the different rf heating techniques are compared; they are contrasted with neutral beam injection, and the feasibility of adiabatic compression as a means of heating plasmas is examined. Separate abstracts were prepared for each chapter of this book. 246 refs.

  19. Plasma heating power dissipation in low temperature hydrogen plasmas

    SciTech Connect

    Komppula, J. Tarvainen, O.

    2015-10-15

    A theoretical framework for power dissipation in low temperature plasmas in corona equilibrium is developed. The framework is based on fundamental conservation laws and reaction cross sections and is only weakly sensitive to plasma parameters, e.g., electron temperature and density. The theory is applied to low temperature atomic and molecular hydrogen laboratory plasmas for which the plasma heating power dissipation to photon emission, ionization, and chemical potential is calculated. The calculated photon emission is compared to recent experimental results.

  20. Vortex formation during rf heating of plasma

    SciTech Connect

    Motley, R.W.

    1980-05-01

    Experiments on a test plasma show that the linear theory of waveguide coupling to slow plasma waves begins to break down if the rf power flux exceeds approx. 30 W/cm/sup 2/. Probe measurements reveal that within 30 ..mu..s an undulation appears in the surface plasma near the mouth of the twin waveguide. This surface readjustment is part of a vortex, or off-center convective cell, driven by asymmetric rf heating of the plasma column.

  1. Complexity Induced Anisotropic Bimodal Intermittent Turbulence in Space Plasmas

    NASA Technical Reports Server (NTRS)

    Chang, Tom; Tam, Sunny W. Y.; Wu, Cheng-Chin

    2004-01-01

    The "physics of complexity" in space plasmas is the central theme of this exposition. It is demonstrated that the sporadic and localized interactions of magnetic coherent structures arising from the plasma resonances can be the source for the coexistence of nonpropagating spatiotemporal fluctuations and propagating modes. Non-Gaussian probability distribution functions of the intermittent fluctuations from direct numerical simulations are obtained and discussed. Power spectra and local intermittency measures using the wavelet analyses are presented to display the spottiness of the small-scale turbulent fluctuations and the non-uniformity of coarse-grained dissipation that can lead to magnetic topological reconfigurations. The technique of the dynamic renormalization group is applied to the study of the scaling properties of such type of multiscale fluctuations. Charged particle interactions with both the propagating and nonpropagating portions of the intermittent turbulence are also described.

  2. Anisotropic N=4 Super-Yang-Mills Plasma and Its Instabilities

    SciTech Connect

    Mateos, David; Trancanelli, Diego

    2011-09-02

    We present a type-IIB supergravity solution dual to a spatially anisotropic finite-temperature N=4 super-Yang-Mills plasma. The solution is static and completely regular. The full geometry can be viewed as a renormalization group flow from an ultraviolet anti-de Sitter geometry to an infrared Lifshitz-like geometry. The anisotropy can be equivalently understood as resulting from a position-dependent {theta} term or from a nonzero number density of dissolved D7-branes. The holographic stress tensor is conserved and anisotropic. The presence of a conformal anomaly plays an important role in the thermodynamics. The phase diagram exhibits homogeneous and inhomogeneous (i.e., mixed) phases. In some regions the homogeneous phase displays instabilities reminiscent of those of weakly coupled plasmas. We comment on similarities with QCD at finite baryon density and with the phenomenon of cavitation.

  3. Jump conditions at fast shocks in an anisotropic magnetized plasma

    NASA Astrophysics Data System (ADS)

    Vogl, D. F.; Erkaev, N. V.; Biernat, H. K.; Mühlbachler, S.; Farrugia, C. J.

    2001-01-01

    In this paper we report on the variations of the magnetic field strength and the plasma parameters across a fast shock as functions of upstream Alfvén Mach numbers and pressure anisotropy downstream of the shock. In our study we consider an oblique shock where the angle between the magnetic field vector and the normal vector upstream of the shock is chosen to be 45°. We further use two threshold conditions of plasma instabilities as additional equations to bound the range of the pressure anisotropy, p⊥/ p|, i.e., the criterion of the mirror instability and that of the fire—hose instability. We found that the variations of the parallel pressure, the parallel temperature, as well as the tangential component of the velocity are most sensitive to the pressure anisotropy downstream of the shock, whereas the variations of the plasma density, the normal velocity, the magnetic field strength, and perpendicular pressure and temperature with respect to the magnetic field show much less pronounced dependence on the anisotropy.

  4. Heat flux viscosity in collisional magnetized plasmas

    SciTech Connect

    Liu, C.; Fox, W.; Bhattacharjee, A.

    2015-05-15

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

  5. Heat flux viscosity in collisional magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Liu, C.; Fox, W.; Bhattacharjee, A.

    2015-05-01

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

  6. Imaginary part of the static gluon propagator in an anisotropic (viscous) QCD plasma

    SciTech Connect

    Dumitru, Adrian; Guo, Yun; Strickland, Michael

    2009-06-01

    We determine viscosity corrections to the retarded, advanced and symmetric gluon self-energies and to the static propagator in the weak-coupling ''hard loop'' approximation to high-temperature QCD. We apply these results to calculate the imaginary part of the heavy-quark potential which is found to be smaller (in magnitude) than at vanishing viscosity. This implies a smaller decay width of quarkonium bound states in an anisotropic plasma.

  7. Drag force of Anisotropic plasma at finite U(1) chemical potential

    NASA Astrophysics Data System (ADS)

    Cheng, Long; Ge, Xian-Hui; Wu, Shang-Yu

    2016-05-01

    We perform the calculation of the drag force acting on a massive quark moving through an anisotropic N=4 SU(N) Super Yang-Mills plasma in the presence of a U(1) chemical potential. We present the numerical results for any value of the anisotropy and arbitrary direction of the quark velocity with respect to the direction of the anisotropy. We find the effect of the chemical potential or charge density will enhance the drag force for our charged solution.

  8. Electron heating in capacitively coupled plasmas revisited

    NASA Astrophysics Data System (ADS)

    Lafleur, T.; Chabert, P.; Booth, J. P.

    2014-06-01

    We revisit the problem of electron heating in capacitively coupled plasmas (CCPs), and propose a method for quantifying the level of collisionless and collisional heating in plasma simulations. The proposed procedure, based on the electron mechanical energy conservation equation, is demonstrated with particle-in-cell simulations of a number of single and multi-frequency CCPs operated in regimes of research and industrial interest. In almost all cases tested, the total electron heating is comprised of collisional (ohmic) and pressure heating parts. This latter collisionless component is in qualitative agreement with the mechanism of electron heating predicted from the recent re-evaluation of theoretical models. Finally, in very electrically asymmetric plasmas produced in multi-frequency discharges, we observe an additional collisionless heating mechanism associated with electron inertia.

  9. Leaky unstable modes and electromagnetic radiation amplification by an anisotropic plasma slab

    SciTech Connect

    Vagin, K. Yu. Uryupin, S. A.

    2015-09-15

    The interaction between electromagnetic radiation and a photoionized plasma slab with an anisotropic electron velocity distribution is studied. It is shown that the fields of leaky modes are amplified due to the development of aperiodic instability in the slab, which leads to an increase in both the reflected and transmitted fields. The transmitted field can significantly increase only if the slab thickness does not exceed the ratio of the speed of light to the electron plasma frequency, whereas there is no upper bound on the slab thickness for the reflected signal to be amplified.

  10. Nanoparticle heating in atmospheric pressure plasmas

    NASA Astrophysics Data System (ADS)

    Kramer, Nicolaas; Aydil, Eray; Kortshagen, Uwe

    2015-09-01

    The plasma environment offers a number of attractive properties that allow for the generation of nanoparticle materials that are otherwise hard to produce by other means. Among these are the generally high temperatures that nanoparticles can attain within plasmas, enabling the generation of nanocrystals of high melting point materials. In low pressure discharges, these high temperatures are the result of energetic surface reactions that strongly heat the small nanoparticles combined with the relatively slow heat transfer to the neutral gas. At atmospheric pressure, the nanoparticle intrinsic temperature is much more closely coupled to the neutral gas temperature. We study the heating of nanoparticles in atmospheric pressure plasmas based on a Monte Carlo simulation that takes into account the most important plasma-surface reactions as well as the conductive cooling of nanoparticles through the neutral gas. We find that, compared to low pressure plasmas, significantly higher plasma densities and densities of reactive species are required in order to achieve nanoparticle temperatures comparable to those in low pressure plasmas. These findings have important implications for the application of atmospheric pressure plasmas for the synthesis of nanoparticle materials. This work was supported by the DOE Plasma Science Center for Predictive Control of Plasma Kinetics.

  11. Anisotropic thermal expansion effects in plasma-sprayed ZrO2-8 percent Y2O3 coatings

    NASA Technical Reports Server (NTRS)

    Berndt, C. C.; Herman, H.

    1983-01-01

    The thermal expansion properties of plasma-sprayed ZrO2-8-wt pct Y2O3 coatings, detached from the substrate, have been examined. Coatings were heat-treated in air or in argon. Anisotropic effects in the longitudinal (planar to the substrate surface) and transverse (perpendicular to the substrate surface) directions were measured and related to the coating structure. The thermal expansion coefficient of the coating is discussed in terms of the material's properties, such as the crack network and interlamellar boundary distribution. A precise model for the expansion behavior of coatings still needs attention, since no description of all of the contributing variables exists. A quantitative analysis of thermal properties of coatings will aid in future design and modeling of coating systems.

  12. The properties of MHD waves and instabilities in solar plasmas with anisotropic temperature and thermal fluxes

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Vladimir; Dzhalilov, Namig

    As confirmed by observations, the temperature anisotropy relative to the magnetic field and the thermal fluxes are typical characteristics of the collisionless and magnetized plasma of the solar corona and solar wind. The properties of such plasma are described in terms of the anisotropic magnetohydrodynamics based on the kinetic equation under the 16-moment approximation. MHD waves and instabilities in the collisionless solar plasma have been analyzed under the aforementioned approximation taking into account the anisotropy of the plasma pressure along and across the magnetic field and the thermal flux along the field. It is established that the thermal flux results in the asymmetry of phase velocities of the compressible wave modes with respect to the outer magnetic field, in a strong interaction between the modes (particularly, between the retrograde modes propagating against the magnetic field), and in oscillatory in-stability of these modes. The thresholds of the mirror and fire-hose instabilities coincide with their kinetic expressions; the increments coincide qualitatively. At a certain propagation angle, the resonance interaction of three retrograde modes (fast sound, slow magnetosound, and slow sound ones) under the occurrence conditions of the classical aperiodic fire-hose instability gives rise to the oscillatory "fire-hose" instability of compressible modes, whose maximum increment may exceed the maximum increment of the classical fire-hose instability. A good agreement of the results obtained in terms of anisotropic MHD with the low-frequency limit of the kinetic description allows us to consider the applied approximation adequate for the description of large-scale dynamics of collisionless anisotropic solar plasma and to use it in the study of waves and instabilities in magnetic tubes and other magnetic features in the solar corona, magnetic reconnection, etc.

  13. On the ordinary mode and whistler mode instabilities in the degenerate anisotropic plasmas

    SciTech Connect

    Iqbal, Z.; Hussain, A.; Murtaza, G.; Tsintsadze, N. L.

    2014-03-15

    Employing Vlasov-Maxwell set of equations, we have investigated the O-mode and whistler mode instability in a degenerate anisotropic magnetoplasma environment and compared the results to those reported for classical plasmas. We propose the excitation of a new banded type of instability for the O-mode case, which grows at some particular values of temperature anisotropy and external magnetic field. For the case of whistler wave, we observe instability saturation mechanism similar to the case of classical plasmas. The existence of both O-mode and whistler mode instability has been observed only for some specific range of unstable wavenumbers. The possible excitation of such instabilities in solid state plasma has been discussed, particularly for semiconductor and semimetal plasmas.

  14. Amplification of whistler waves propagating through inhomogeneous, anisotropic, mirror-confined hot-electron plasmas

    SciTech Connect

    Guest, G.E.; Miller, R.L.

    1988-12-01

    A fully relativistic local dispersion relation for whistler waves has been solved at closely spaced points along the magnetic field lines of a 2:1 magnetic mirror in which a highly anisotropic, spatially inhomogeneous, hot-electron plasma is confined. The limiting plasma parameters for convective (spatial)= growth have been determined numerically and used to identify plasma conditions leading to maximum amplification of input microwave signals introduced in the form of whistler waves. The maximum gain has been evaluated numerically for a range of values of the hot-electron plasma within which all major stability criteria are satisfied. Very high gains (approx.40 dB) are indicated over the entire range of beta investigated.

  15. Anisotropic heat transport in nanoconfined polyamide-6,6 oligomers: atomistic reverse nonequilibrium molecular dynamics simulation.

    PubMed

    Eslami, Hossein; Mohammadzadeh, Laila; Mehdipour, Nargess

    2012-03-14

    While polymers are known as thermal insulators, recent studies show that stretched single chains of polymers have a very high thermal conductivity. In this work, our new simulation scheme for simulation of heat flow in nanoconfined fluids [H. Eslami, L. Mohammadzadeh, and N. Mehdipour, J. Chem. Phys. 135, 064703 (2011)] is employed to study the effect of chain ordering (stretching) on the rate of heat transfer in polyamide-6,6 nanoconfined between graphene surfaces. Our results for the heat flow in the parallel direction (the plane of surfaces) show that the coefficient of thermal conductivity depends on the intersurface distance and is much higher than that of the bulk polymer. A comparison of results in this work with our former findings on the heat flow in the perpendicular direction, with the coefficient of heat conductivity less than the bulk sample, reveal that well-organized polymer layers between the confining surfaces show an anisotropic heat conduction; the heat conduction in the direction parallel to the surfaces is much higher than that in the perpendicular direction. The origin of such anisotropy in nanometric heat flow is shown to be the dramatic anisotropy in chain conformations (chain stretching) beside the confining surfaces. The results indicate that the coefficients of heat conductivity in both directions, normal and parallel to the surfaces, depend on the degree of polymer layering between the surfaces and the pore width. PMID:22423855

  16. Geodesic acoustic mode in anisotropic plasmas using double adiabatic model and gyro-kinetic equation

    SciTech Connect

    Ren, Haijun; Cao, Jintao

    2014-12-15

    Geodesic acoustic mode in anisotropic tokamak plasmas is theoretically analyzed by using double adiabatic model and gyro-kinetic equation. The bi-Maxwellian distribution function for guiding-center ions is assumed to obtain a self-consistent form, yielding pressures satisfying the magnetohydrodynamic (MHD) anisotropic equilibrium condition. The double adiabatic model gives the dispersion relation of geodesic acoustic mode (GAM), which agrees well with the one derived from gyro-kinetic equation. The GAM frequency increases with the ratio of pressures, p{sub ⊥}/p{sub ∥}, and the Landau damping rate is dramatically decreased by p{sub ⊥}/p{sub ∥}. MHD result shows a low-frequency zonal flow existing for all p{sub ⊥}/p{sub ∥}, while according to the kinetic dispersion relation, no low-frequency branch exists for p{sub ⊥}/p{sub ∥}≳ 2.

  17. Numerical modeling of waveguide heated microwave plasmas

    SciTech Connect

    Venkateswaran, S.; Schwer, D.A.; Merkle, C.L.

    1993-12-01

    Waveguide-heated microwave plasmas for space propulsion applications are analyzed by a two-dimensional numerical solution of the combined Navier-Stokes and Maxwell equations. Two waveguide configurations -- one purely transmitting and the other with a reflecting end wall -- are considered. Plasma stability and absorption characteristics are studied and contrasted with the characteristic of resonant cavity heated plasmas. In addition, preliminary estimates of the overall efficiency and the thrust and specific impulse of the propulsion system are also made. The computational results are used to explain experimental trends and to better understand the working of these devices.

  18. APPARATUS FOR HEATING A PLASMA

    DOEpatents

    Stix, T.H.

    1962-01-01

    The system contemplates the use of ion cyclotron motions for transferring energy to a plasma immersed in a confining magnetic field such as is found in thermonuclear reactors of the stellarator class. Oppositely directed windings are provided for producing ion-accelerating fields having a time and spatial periodicity and these have the advantage of producing ion cyclotron motions without the development of space charges which preclude the efficient energy transfer to the plasma. (AEC)

  19. Low beta equilibrium and stability for anisotropic pressure closed field line plasma confinement systems

    SciTech Connect

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

    1994-05-01

    General formalism is developed to analyze the equilibrium and stability of low beta anisotropic pressure plasmas confined in closed field line magnetic systems. The formalism allows one to consider rather general magnetic systems with nonuniform axis curvature and longitudinal profiles of toroidal and multipole poloidal field. It also allows having a strong pressure anisotropy corresponding to enhanced plasma pressure in mirror cells of the system. As an example of such a system the authors consider the recently proposed linked mirror neutron source (LMNS). Application of the above formalism to the LMNS analysis confirms most of the preliminary results, however, they obtain a considerable reduction of mirror cell axis curvature and an appreciable ellipticity of plasma cross-section in the mirror cell midplane. They have also optimized the longitudinal pressure and magnetic field distribution.

  20. Anisotropic Specific Heat of CoNb2O6 in Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Hanawa, Takeshi; Shinkawa, Kohtaro; Ishikawa, Masayasu; Miyatani, Kazuo; Saito, Kazuhiro; Kohn, Kay

    1994-07-01

    We investigated the successive magnetic phase transitions of CoNb2O6 at 2.9 K and 1.9 K by measuring the specific heat, magnetic susceptibility and magnetization of poly- and single-crystalline samples. The specific heat measurements performed in external magnetic fields up to about 1.5 kOe disclosed the Ising-like nature of the transitions and tremendous anisotropic magnetic-field dependence due to the low-dimensional character. Moreover, the specific heat and ac magnetic susceptibility data imply another magnetic state below 1 K. These consequences suggest a very interesting magnetic phase diagram, resulting from the competing single-ion anisotropy and exchange interactions in this compound.

  1. Anisotropic distribution function of minority tail ions generated by strong ion-cyclotron resonance heating

    SciTech Connect

    Chang, C.S.; Colestock, P.

    1989-05-01

    The highly anisotropic particle distribution function of minority tail ions driven by ion-cyclotron resonance heating at the fundamental harmonic is calculated in a two-dimensional velocity space. It is assumed that the heating is strong enough to drive most of the resonant ions above the in-electron critical slowing-down energy. Simple analytic expressions for the tail distribution are obtained fro the case when the Doppler effect is sufficiently large to flatten the sharp pitch angle dependence in the bounce averaged qualilinear heating coefficient, D/sub b/, and for the case when D/sub b/ is assumed to be constant in pitch angle and energy. It is found that a simple constant-D/sub b/ solution can be used instead of the more complicated sharp-D/sub b/ solution for many analytic purposes. 4 refs., 4 figs.

  2. Effects of anisotropic conduction and heat pipe interaction on minimum mass space radiators

    NASA Technical Reports Server (NTRS)

    Baker, Karl W.; Lund, Kurt O.

    1991-01-01

    Equations are formulated for the two dimensional, anisotropic conduction of heat in space radiator fins. The transverse temperature field was obtained by the integral method, and the axial field by numerical integration. A shape factor, defined for the axial boundary condition, simplifies the analysis and renders the results applicable to general heat pipe/conduction fin interface designs. The thermal results are summarized in terms of the fin efficiency, a radiation/axial conductance number, and a transverse conductance surface Biot number. These relations, together with those for mass distribution between fins and heat pipes, were used in predicting the minimum radiator mass for fixed thermal properties and fin efficiency. This mass is found to decrease monotonically with increasing fin conductivity. Sensitivities of the minimum mass designs to the problem parameters are determined.

  3. Magnetorotational instability in a collisionless plasma with heat flux vector and an isotropic plasma with self-gravitational effect

    SciTech Connect

    Ren Haijun; Wu Zhengwei; Cao Jintao; Chu, Paul K.

    2011-09-15

    The linear stability of a differential rotating magnetized plasma is analyzed in the collisionless approximation along with heat flux vector. The dispersion relation is derived and simplified cases are discussed with instability criteria presented. Anisotropic pressures are shown to not only alter the classical instability criterion but also induce new unstable regions. The shear rotating instability in a collisional magnetized plasma with a scalar kinetic pressure in the presence of self-gravitational effect is then considered. Three cases are discussed specifically according to the general dispersion relation. The effects of Jeans term and compressibility on the local shear instability induced by differential rotation are examined and the analytic instability criteria are presented.

  4. Magnetorotational instability in a collisionless plasma with heat flux vector and an isotropic plasma with self-gravitational effect

    NASA Astrophysics Data System (ADS)

    Ren, Haijun; Cao, Jintao; Wu, Zhengwei; Chu, Paul K.

    2011-09-01

    The linear stability of a differential rotating magnetized plasma is analyzed in the collisionless approximation along with heat flux vector. The dispersion relation is derived and simplified cases are discussed with instability criteria presented. Anisotropic pressures are shown to not only alter the classical instability criterion but also induce new unstable regions. The shear rotating instability in a collisional magnetized plasma with a scalar kinetic pressure in the presence of self-gravitational effect is then considered. Three cases are discussed specifically according to the general dispersion relation. The effects of Jeans term and compressibility on the local shear instability induced by differential rotation are examined and the analytic instability criteria are presented.

  5. Anisotropic thermal-diffusivity measurements by a new laser-spot-heating technique

    NASA Astrophysics Data System (ADS)

    Kato, Hideyuki; Baba, Tetsuya; Okaji, Masahiro

    2001-12-01

    A new technique to measure thermal diffusivities of solid materials, including their anisotropic behaviours, has been developed. The technique is based on periodic heating: an intensity-modulated laser beam is focused to make a small heat spot on the front side of a thin-plate specimen and the excited temperature waves are detected by a thin thermocouple attached onto its rear side. The phase lag of temperature waves is monitored as a function of the distance between the heated spot and the sensing point. The accuracy and the applicability of the present technique were well verified by using two kinds of isotropic reference samples, an austenitic stainless steel and pure copper. The typical uncertainty is estimated to be 5% at room temperature. This technique was applied to evaluate the highly anisotropic thermal diffusivity of highly oriented pyrolytic graphite (HOPG). Its anisotropy, Dab/Dc (the ratio of the in-plane thermal diffusivity to the out-of-plane one), was observed to be about 220.

  6. Dispersive Alfvén waves in a plasma with anisotropic superthermal particles

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Wang, Y. F.; Hu, T. P.

    2016-04-01

    The dispersion of dispersive Alfvén wave in a low β plasma with anisotropic superthermal particles modeled by a bi-nonextensive distribution is derived from a kinetic way. The effect of anisotropic temperature on inertial Alfvén wave is so small that it is negligible. However, it will play an important role on the property of kinetic Alfvén wave (KAW). The numerical results reveal that the presence of superthermal electrons in the small wavenumber limit will lead the damping rate of the KAW bigger than the one with Maxwellian distribution. Whereas, the damping rate of KAW in the large wavenumber limit will decrease with the presence of superthermal electrons. When the effect of electron anisotropic temperature overwhelms the effect of finite ion gyroradius in the small wavenumber regime, the damping rate of KAW grows with the presence of electron temperature anisotropy. On the other hand, when the effects of finite ion gyroradius play a dominant role in the large wavenumber regime, the damping rate of KAW increases with the effective perpendicular and parallel electron temperatures.

  7. Plasma arc heated secondary combustion chamber

    SciTech Connect

    Haun, R.; Paulson, B.; Schlienger, M.; Goerz, D.; Kerns, J.; Vernazza, J.

    1995-02-01

    This paper describes a secondary combustion chamber (SCC) for hazardous waste treatment systems that uses a plasma arc torch as the heat source. Developed under a cooperative research and development agreement (CRADA) between Retech, Inc. and Lawrence Livermore National Laboratory (LLNL), the unit is intended primarily to handle the off-gas from a Plasma Arc Centrifugal Treatment (PACT) system. ft is designed to heat the effluent gas which may contain volatile organic compounds, and maintain the gas temperature above 1000 C for two seconds or more. The benefits of using a plasma arc gas heater are described in comparison to a conventional fossil fuel heated SCC. Thermal design considerations are discussed. Analysis and experimental results are presented to show the effectiveness in destroying hazardous compounds and reducing the total volume of gaseous emissions.

  8. RF plasma heating improvement with EBG surfaces

    NASA Astrophysics Data System (ADS)

    Guadamuz, Saul; Milanesio, Daniele; Maggiora, Riccardo

    2008-11-01

    High impedance surfaces or electromagnetic band gap (EBG) surfaces have proved themselves to be useful in wireless communications applications due to their unique characteristics such as no propagating surface wave support, no conduction of RF current for a given bandwidth, in-phase electromagnetic reflection and non-inverted image of the electric charge in front of them [1]. These characteristics make possible to design compact antennas achieving better performance in terms of radiation and input impedance. ICRF plasma heating antennas in fusion experiments can take advantage of using EBG surfaces. One of the main issues in ICRF plasma heating is the low power coupling of the plasma facing antenna. The adoption of EBG surfaces in the antenna structure and the advantages offered by a predictive designing tool as TOPICA [2] offer the possibility to improve significantly the coupled power to plasma. [1] IEEE Trans. Microwave Theory Tech., vol. 47, pp. 2059--2074, Nov. 1999. [2] Nucl. Fusion, 46 (2006) S476.

  9. Numerical study of heat and mass transfer in an anisotropic porous enclosure due to constant heating and cooling

    SciTech Connect

    Bera, P.; Eswaran, V.; Singh, P.

    1998-12-01

    Combined heat and mass transfer in porous media occurs in many natural phenomena and engineering applications, such as the migration of moisture through air contained in insulation, the spreading of chemical pollutants in saturated soil, and the extraction of geothermal energy. Here, double-diffusive natural convective flow within a rectangular enclosure has been studied for an anisotropic porous medium using a non-Darcy extension. The principal direction of the permeability tensor has been taken oblique to the gravity vector. The spectral element method has been used to solve the problem numerically. The method has been validated using existing analytical and numerical results. Parametric studies are presented for isotropic and anisotropic cases for different fundamental parameters, e.g., buoyancy ratio, Lewis number, Rayleigh number, Darcy number. The results show that anisotropy causes significant changes in the Nusselt and Sherwood numbers. In particular, the present analysis shows that permeability orientation angle has a significant effect on the flow rate and, consequently, on the heat and mass transfer.

  10. Stable anisotropic plasma confinement in magnetic configurations with convex-concave field lines

    NASA Astrophysics Data System (ADS)

    Tsventoukh, M. M.

    2014-02-01

    It is shown that a combination of the convex and the concave part of a field line provides a strong stabilizing action against convective (flute-interchange) plasma instability (Tsventoukh 2011 Nucl. Fusion 51 112002). This results in internal peaking of the stable plasma pressure profile that is calculated from the collisionless kinetic stability criterion for any magnetic confinement system with combination of mirrors and cusps. Connection of the convex and concave field line parts results in a reduction of the space charge that drives the unstable E × B motion, as there is an opposite direction of the particle drift in a non-uniform field at convex and concave field lines. The pressure peaking arises at the minimum of the second adiabatic invariant J that takes place at the ‘middle’ of a tandem mirror-cusp transverse cross-section. The position of the minimum in J varies with the particle pitch angle that results in a shift of the peaking position depending on plasma anisotropy. This allows one to improve a stable peaked pressure profile at a convex-concave field by changing the plasma anisotropy over the trap cross-section. Examples of such anisotropic distribution functions are found that give an additional substantial enhancement in the maximal central pressure. Furthermore, the shape of new calculated stable profiles has a wide central plasma layer instead of a narrow peak.

  11. Monte Carlo prediction of radiative heat transfer in inhomogeneous, anisotropic, nongray media

    NASA Technical Reports Server (NTRS)

    Farmer, Jeff T.; Howell, John R.

    1994-01-01

    A Monte Carlo solution technique has been formulated to predict the radiative heat transfer in three-dimensional, inhomogeneous participating media which exhibit spectrally dependent emission and absorption and anisotropic scattering. Details of the technique and selected numerical sensitivities are discussed. The technique was applied to a problem involving a medium composed of a gas mixture of carbon dioxide and nitrogen and suspended carbon particles. A homogeneous medium was modeled to examine the effect of total pressure and carbon-particle concentration on radiative heat transfer. Variation in total pressure, over the range studied, had minimal effect on the amount of heat radiated to the enclosure walls and on the radiative-flux distribution within the medium. Increases in the carbon particle concentration produced significantly higher heat fluxes at the boundaries and altered the radiative flux distribution. The technique was then applied to an inhomogeneous medium to examine effects of specific temperature and carbon particle concentration distributions on radiative heat transfer. For the inhomogeneous conditions examined, the largest radiative flux divergence occurs near the center of the medium and the regions near some enclosure walls act as energy sinks.

  12. Laser-heated emissive plasma probe.

    PubMed

    Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K

    2008-08-01

    Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808 nm wavelength and an output power up to 50 W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge. PMID:19044350

  13. Plasma treatment of heat-resistant materials

    NASA Astrophysics Data System (ADS)

    Vlasov, V. A.; Kosmachev, P. V.; Skripnikova, N. K.; Bezukhov, K. A.

    2015-11-01

    Refractory lining of thermal generating units is exposed to chemical, thermal, and mechanical attacks. The degree of fracture of heat-resistant materials depends on the chemical medium composition, the process temperature and the material porosity. As is known, a shortterm exposure of the surface to low-temperature plasma (LTP) makes possible to create specific coatings that can improve the properties of workpieces. The aim of this work is to produce the protective coating on heat-resistant chamotte products using the LTP technique. Experiments have shown that plasma treatment of chamotte products modifies the surface, and a glass-ceramic coating enriched in mullite is formed providing the improvement of heat resistance. For increasing heat resistance of chamotte refractories, pastes comprising mixtures of Bacor, alumina oxide, and chamot were applied to their surfaces in different ratios. It is proved that the appropriate coating cannot be created if only one of heat-resistant components is used. The required coatings that can be used and recommended for practical applications are obtained only with the introduction of powder chamot. The paste composition of 50% chamot, 25% Bacor, and 25% alumina oxide exposed to plasma treatment, has demonstrated the most uniform surface fusion.

  14. Plasma waves in a relativistic, strongly anisotropic plasma propagated along a strong magnetic field

    NASA Technical Reports Server (NTRS)

    Onishchenko, O. G.

    1980-01-01

    The dispersion properties of plasma waves in a relativistic homogeneous plasma propagated along a strong magnetic field are studied. It is shown that the non-damping plasma waves exist in the frequency range omega sub p or = omega or = omega sub L. The values of omega sub p and omega sub L are calculated for an arbitrary homogeneous relativistic function of the particle distribution. In the case of a power ultrarelativistic distribution, it is shown that, if the ultrarelativistic tail of the distribution drops very rapidly, slightly damping plasma waves are possible with the phase velocity (omega/K)c.

  15. Plasma heating with crossing relativistic electron beams

    NASA Astrophysics Data System (ADS)

    Ratan, Naren; Sircombe, Nathan; Ceurvorst, Luke; Kasim, Muhammad; Sadler, James; Bingham, Robert; Trines, Raoul; Norreys, Peter

    2015-11-01

    Plasma heating by relativistic electron beams is a powerful tool with applications including the heating of inertial confinement fusion targets and the study of matter in extreme conditions. We discuss the use of two relativistic electron beams to efficiently heat the plasma ions where the beams cross by using beam-plasma instabilities and non-linear wave coupling between Langmuir and ion-acoustic waves. Energy from the electron beams is coupled to the plasma ions as the beams become unstable and drive Langmuir waves which couple non-linearly to ion-acoustic waves which are then damped . Results of linear growth rate calculations are presented for the system of two crossing electron beams demonstrating a broad spectrum of unstable modes. Relativistic Vlasov-Maxwell simulations in two space and two momentum dimensions have been performed which demonstrate the non-linear coupling of the electron beam energy into ion-acoustic waves and the energy cascade to the background ions. Time-frequency analysis is applied to analyze the non-linear coupling between Langmuir and ion-acoustic waves in wave phase space. Structural properties of the strong turbulence produced at late times are analyzed.

  16. The anisotropic redistribution of free energy for gyrokinetic plasma turbulence in a Z-pinch

    NASA Astrophysics Data System (ADS)

    Navarro, Alejandro Bañón; Teaca, Bogdan; Jenko, Frank

    2016-04-01

    For a Z-pinch geometry, we report on the nonlinear redistribution of free energy across scales perpendicular to the magnetic guide field, for a turbulent plasma described in the framework of gyrokinetics. The analysis is performed using a local flux-surface approximation, in a regime dominated by electrostatic fluctuations driven by the entropy mode, with both ion and electron species being treated kinetically. To explore the anisotropic nature of the free energy redistribution caused by the emergence of zonal flows, we use a polar coordinate representation for the field-perpendicular directions and define an angular density for the scale flux. Positive values for the classically defined (angle integrated) scale flux, which denote a direct energy cascade, are shown to be also composed of negative angular sections, a fact that impacts our understanding of the backscatter of energy and the way in which it enters the modeling of sub-grid scales for turbulence. A definition for the flux of free energy across each perpendicular direction is introduced as well, which shows that the redistribution of energy in the presence of zonal flows is highly anisotropic.

  17. Hybrid Model of Inhomogeneous Solar Wind Plasma Heating by Alfven Wave Spectrum: Parametric Studies

    NASA Technical Reports Server (NTRS)

    Ofman, L.

    2010-01-01

    Observations of the solar wind plasma at 0.3 AU and beyond show that a turbulent spectrum of magnetic fluctuations is present. Remote sensing observations of the corona indicate that heavy ions are hotter than protons and their temperature is anisotropic (T(sub perpindicular / T(sub parallel) >> 1). We study the heating and the acceleration of multi-ion plasma in the solar wind by a turbulent spectrum of Alfvenic fluctuations using a 2-D hybrid numerical model. In the hybrid model the protons and heavy ions are treated kinetically as particles, while the electrons are included as neutralizing background fluid. This is the first two-dimensional hybrid parametric study of the solar wind plasma that includes an input turbulent wave spectrum guided by observation with inhomogeneous background density. We also investigate the effects of He++ ion beams in the inhomogeneous background plasma density on the heating of the solar wind plasma. The 2-D hybrid model treats parallel and oblique waves, together with cross-field inhomogeneity, self-consistently. We investigate the parametric dependence of the perpendicular heating, and the temperature anisotropy in the H+-He++ solar wind plasma. It was found that the scaling of the magnetic fluctuations power spectrum steepens in the higher-density regions, and the heating is channeled to these regions from the surrounding lower-density plasma due to wave refraction. The model parameters are applicable to the expected solar wind conditions at about 10 solar radii.

  18. Investigation on broadband propagation characteristic of terahertz electromagnetic wave in anisotropic magnetized plasma in frequency and time domain

    SciTech Connect

    Tian, Yuan; Han, Yiping; Ai, Xia; Liu, Xiuxiang

    2014-12-15

    In this paper, we investigate the propagation of terahertz (THz) electromagnetic wave in an anisotropic magnetized plasma by JE convolution-finite difference time domain method. The anisotropic characteristic of the plasma, which leads to right-hand circularly polarized (RCP) and right-hand circularly polarized (LCP) waves, has been taken into account. The interaction between electromagnetic waves and magnetized plasma is illustrated by reflection and transmission coefficients for both RCP and LCP THz waves. The effects of both the magnetized plasma thickness and the external magnetized field are analyzed and numerical results demonstrate that the two factors could influence the THz wave greatly. It is worthy to note that besides the reflection and transmission coefficients in the frequency domain, the waveform of the electric field in the time domain varying with thicknesses and external magnetic fields for different polarized direction has been studied.

  19. Phase transitions of an anisotropic N=4 super Yang-Mills plasma via holography

    NASA Astrophysics Data System (ADS)

    Banks, Elliot

    2016-07-01

    Black hole solutions of type IIB supergravity were previously found that are dual to N=4 supersymmetric Yang-Mills plasma with an anisotropic spatial deformation. In the zero temperature limit, these black holes approach a Liftshitz like scaling solution in the IR. It was recently shown that these black holes are unstable, and at low temperatures there is a new class of black hole solutions that are thermodynamically preferred. We extend this analysis, by considering consistent truncations of the Kaluza-Klein reduction of IIB supergravity on a five-sphere that preserves multiple scalar and U(1) gauge fields. We show that the previously constructed black holes become unstable at low temperatures, and construct new classes of exotic black hole solutions. We study the DC thermo-electric conductivity of these U(1) charged black holes, and find a diverging DC conductivity at zero temperature due to the divergence of the gauge field coupling.

  20. A new phase for the anisotropic N=4 super Yang-Mills plasma

    NASA Astrophysics Data System (ADS)

    Banks, Elliot; Gauntlett, Jerome P.

    2015-09-01

    Black hole solutions of type IIB supergravity have been previously constructed that describe the N=4 supersymmetric Yang-Mills plasma with an anisotropic spatial deformation. The zero temperature limit of these black holes approach a Lifshitz-like scaling solution in the infrared. We show that these black holes become unstable at low temperature and we construct a new class of black hole solutions which are thermodynamically preferred. The phase transition is third order and incorporates a spontaneous breaking of the SO(6) global symmetry down to SO(4) × SO(2). The critical exponents for the phase transition are given by ( α, β, γ, δ) = (-1, 1, 1, 2) which differ from the standard mean-field exponents usually seen in holography. At low temperatures the black holes approach a novel kind of scaling behaviour in the far IR with spatial anisotropy and hyperscaling violation. We show that the new ground states are thermal insulators in the direction of the anisotropy.

  1. Three discontinuous Galerkin schemes for the anisotropic heat conduction equation on non-aligned grids

    NASA Astrophysics Data System (ADS)

    Held, M.; Wiesenberger, M.; Stegmeir, A.

    2016-02-01

    We present and discuss three discontinuous Galerkin (dG) discretizations for the anisotropic heat conduction equation on non-aligned cylindrical grids. Our non-aligned scheme relies on a self-adjoint local dG (LDG) discretization of the elliptic operator. It conserves the energy exactly and converges with arbitrary order. The pollution by numerical perpendicular heat fluxes decreases with superconvergence rates. We compare this scheme with aligned schemes that are based on the flux-coordinate independent approach for the discretization of parallel derivatives. Here, the dG method provides the necessary interpolation. The first aligned discretization can be used in an explicit time-integrator. However, the scheme violates conservation of energy and shows up stagnating convergence rates for very high resolutions. We overcome this partly by using the adjoint of the parallel derivative operator to construct a second self-adjoint aligned scheme. This scheme preserves energy, but reveals unphysical oscillations in the numerical tests, which result in a decreased order of convergence. Both aligned schemes exhibit low numerical heat fluxes into the perpendicular direction and are superior for flute-modes with finite parallel gradients. We build our argumentation on various numerical experiments on all three schemes for a general axisymmetric magnetic field, which is closed by a comparison to the aligned finite difference (FD) schemes of Stegmeir et al. (2014) and Stegmeir et al. (submitted for publication).

  2. Ion heating in a plasma focus

    NASA Technical Reports Server (NTRS)

    Hohl, F.; Gary, S. P.

    1974-01-01

    Ion acceleration and heating in a plasma focus were investigated by the numerical integration of the three-dimensional equations of motion. The electric and magnetic fields given were derived from experimental data. The results obtained show that during the collapse phase of focus formation, ions are efficiently heated to temperatures of several keV. During the phase of rapid current reduction, ions are accelerated to large velocities in the axial direction. The results obtained with the model are in general agreement with experimental results.

  3. Asymptotic-preserving Lagrangian approach for modeling anisotropic transport in magnetized plasmas for arbitrary magnetic fields

    NASA Astrophysics Data System (ADS)

    Chacon, Luis; Del-Castillo-Negrete, Diego; Hauck, Cory

    2012-10-01

    Modeling electron transport in magnetized plasmas is extremely challenging due to the extreme anisotropy between parallel (to the magnetic field) and perpendicular directions (χ/χ˜10^10 in fusion plasmas). Recently, a Lagrangian Green's function approach, developed for the purely parallel transport case,footnotetextD. del-Castillo-Negrete, L. Chac'on, PRL, 106, 195004 (2011)^,footnotetextD. del-Castillo-Negrete, L. Chac'on, Phys. Plasmas, 19, 056112 (2012) has been extended to the anisotropic transport case in the tokamak-ordering limit with constant density.footnotetextL. Chac'on, D. del-Castillo-Negrete, C. Hauck, JCP, submitted (2012) An operator-split algorithm is proposed that allows one to treat Eulerian and Lagrangian components separately. The approach is shown to feature bounded numerical errors for arbitrary χ/χ ratios, which renders it asymptotic-preserving. In this poster, we will present the generalization of the Lagrangian approach to arbitrary magnetic fields. We will demonstrate the potential of the approach with various challenging configurations, including the case of transport across a magnetic island in cylindrical geometry.

  4. FREQUENCY CONTROL OF RF HEATING OF GASEOUS PLASMA

    DOEpatents

    Herold, E.W.

    1962-09-01

    This invention relates to the heating of gaseous plasma by radiofrequency ion-cyclotron resonance heating. The cyclotron resonance frequencies are varied and this invention provides means for automatically controlling the frequency of the radiofrequency to maximize the rate of heating. To this end, a servo-loop is provided to sense the direction of plasma heating with frequency and a control signal is derived to set the center frequency of the radiofrequency energy employed to heat the plasma. (AEC)

  5. The heating of plasma focus electrodes

    NASA Astrophysics Data System (ADS)

    Angeli, E.; Frignani, M.; Mannucci, S.; Rocchi, F.; Sumini, M.; Tartari, A.

    2006-02-01

    Plasma focus (PF) technology development today is strictly related to the possibility of a high frequency repetitive working regime. One of the more relevant obstacles to this goal is the heating of structural components due to direct interaction with plasma. In this paper, temperature decay measurements of the inner electrode of a 7 kJ Mather type PF are presented. Data from several series of shots at different bank energies are analysed and compared with theoretical and numerical models. Two possible scale laws are derived from the experimental data to correlate thermal deposition with bank energy. It is found that a fraction of about 10% of total energy is released to the inner electrode. Finally, after some considerations about the cooling and heating mechanisms, an analysis on maximum temperature sustained by materials is presented.

  6. Investigation of anisotropic photonic band gaps in three-dimensional magnetized plasma photonic crystals containing the uniaxial material

    SciTech Connect

    Zhang, Hai-Feng; Liu, Shao-Bin; Kong, Xiang-Kun

    2013-09-15

    In this paper, the dispersive properties of three-dimensional (3D) magnetized plasma photonic crystals (MPPCs) composed of anisotropic dielectric (the uniaxial material) spheres immersed in homogeneous magnetized plasma background with face-centered-cubic (fcc) lattices are theoretically investigated by the plane wave expansion method, as the Voigt effects of magnetized plasma are considered. The equations for calculating the anisotropic photonic band gaps (PBGs) in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and two flatbands regions can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency, and external magnetic field on the dispersive properties of the 3D MPPCs are investigated in detail, respectively, and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in 3D MPPCs with fcc lattices and the complete PBGs can be found compared to the conventional 3D MPPCs doped by the isotropic material. The bandwidths of PBGs can be tuned by introducing the magnetized plasma into 3D PCs containing the uniaxial material. It is also shown that the anisotropic PBGs can be manipulated by the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency, and external magnetic field, respectively. The locations of flatbands regions cannot be manipulated by any parameters except for the plasma frequency and external magnetic field. Introducing the uniaxial material can obtain the complete PBGs as the 3D MPPCs with high symmetry and also provides a way to design the tunable devices.

  7. Theory of ballooning-mirror instabilities for anisotropic pressure plasmas in the magnetosphere

    SciTech Connect

    Cheng, C.Z.; Qian, Q.

    1993-09-01

    This paper deals with a kinetic-MHD eigenmode stability analysis of low frequency ballooning-mirror instabilities for anisotropic pressure plasmas in the magnetosphere. The ballooning mode is a dominant transverse wave driven unstable by pressure gradient in the bad curvature region. The mirror mode with a dominant compressional magnetic field perturbation is excited when the product of plasma beta and pressure anisotropy is large. The field-aligned eigenmode equations take into account the coupling of the transverse and compressional components of the perturbed magnetic field and describe the coupled ballooning-mirror mode. Because the energetic trapped ions precess very rapidly across the {rvec B} field, their motion becomes very rigid with respect to low frequency MHD perturbations with symmetric structure of parallel perturbed magnetic field {delta}B{sub {parallel}} and electrostatic potential {Phi} along the north-south ambient magnetic field, and the symmetric ballooning-mirror mode is shown to be stable. On the other hand, the ballooning-mirror mode with antisymmetric {delta}B{sub {parallel}}, and {Phi} structure along the north-south ambient magnetic field is only weakly influenced by energetic trapped particle kinetic effects due to rapid trapped particle bounce motion and has the lowest instability threshold determined by MHD theory. With large plasma beta ({beta}{sub {parallel}} {ge} O(1)) and pressure anisotropy (P{sub {perpendicular}}/P{sub {parallel}} > 1) at equator the antisymmetric ballooning-mirror mode structures resemble the field-aligned wave structures of the multisatellite observations of a long lasting compressional Pc 5 wave event during November 14--15, 1979 [Takahashi et al.]. The study provides the theoretical basis for identifying the internal excitation mechanism of ULF (Pc 4-5) waves by comparing the plasma stability parameters computed from the satellite particle data with the theoretical values.

  8. Inertial-range kinetic turbulence in pressure-anisotropic astrophysical plasmas

    NASA Astrophysics Data System (ADS)

    Kunz, M. W.; Schekochihin, A. A.; Chen, C. H. K.; Abel, I. G.; Cowley, S. C.

    2015-10-01

    > A theoretical framework for low-frequency electromagnetic (drift-)kinetic turbulence in a collisionless, multi-species plasma is presented. The result generalises reduced magnetohydrodynamics (RMHD) and kinetic RMHD (Schekochihin et al., Astrophys. J. Suppl. Ser., vol. 182, 2009, pp. 310-377) to the case where the mean distribution function of the plasma is pressure-anisotropic and different ion species are allowed to drift with respect to each other - a situation routinely encountered in the solar wind and presumably ubiquitous in hot dilute astrophysical plasmas such as the intracluster medium. Two main objectives are achieved. First, in a non-Maxwellian plasma, the relationships between fluctuating fields (e.g. the Alfvén ratio) are order-unity modified compared to the more commonly considered Maxwellian case, and so a quantitative theory is developed to support quantitative measurements now possible in the solar wind. Beyond these order-unity corrections, the main physical feature of low-frequency plasma turbulence survives the generalisation to non-Maxwellian distributions: Alfvénic and compressive fluctuations are energetically decoupled, with the latter passively advected by the former; the Alfvénic cascade is fluid, satisfying RMHD equations (with the Alfvén speed modified by pressure anisotropy and species drifts), whereas the compressive cascade is kinetic and subject to collisionless damping (and for a bi-Maxwellian plasma splits into three independent collisionless cascades). Secondly, the organising principle of this turbulence is elucidated in the form of a conservation law for the appropriately generalised kinetic free energy. It is shown that non-Maxwellian features in the distribution function reduce the rate of phase mixing and the efficacy of magnetic stresses, and that these changes influence the partitioning of free energy amongst the various cascade channels. As the firehose or mirror instability thresholds are approached, the dynamics

  9. Heat and Products Induced by Plasma Electrolysis

    SciTech Connect

    Tadahiko Mizuno; Tadayoshi Ohmori; Tadashi Akimoto; Akito Takahashi

    2000-11-12

    Plasma is formed on an electrode surface when a metal cathode is polarized in high-voltage electrolysis in a liquid electrolyte. When a liquid electrolyte is polarized at high voltage (70 to 500 V), it gives rise to an electric discharge and a plasma state. We measured the output heat and input electric power in real time by a method that combined open cell isoperibolic calorimetry and flow calorimetry. Takahashi et al. hypothesize a nuclear reaction induced by photon activation on the cathode element. We have attempted to explain the experimental results by a mechanism that produces no radioactive materials or weak radioactive emission. We applied the Takahashi theory developed for Pd and Au electrodes to the case of a W electrode. We have first reported that the distribution for their reaction product showed clearly one or two peaks that consisted of the mass number around 52 for the case of Pd and 64 and 120 for Au. This paper mainly pertains to the metal electrode. With a tungsten electrode, one peak in the anomalous elements is for the major elements from 40 to 65, and the other is from 100 to 120. The total mass of elements generated during excess heat evolution was on the order of 1 mg. Based on this mass, according to conventional laws of fission and fusion, 'commensurate' heat would have been on the order of 10{sup 6} to 10{sup 7} J. The actual excess heat was typically estimated at 10{sup 5}-several orders of magnitude less than the expected value. It is still difficult to calculate the actual weight loss of the reactive material before and after the reaction. However, we can say that the total energy generated was much less than the value calculated from the produced weight. We conclude that the photofission mechanism explains the amount of excess heat and the distribution of the element generation during the electrochemical treatment.

  10. The influence of thermophysical properties of an anisotropic heat-element substrate on the value of thermal emf in the stationary thermal mode

    NASA Astrophysics Data System (ADS)

    Bobashev, S. V.; Popov, P. A.; Reznikov, B. I.; Sakharov, V. A.

    2016-05-01

    Thermal and thermoelectric processes in anisotropic heat elements located on substrates made of different materials have been numerically simulated. It is shown that, when an invariable heat flux passes through a heat element, the thermophysical properties of the substrate and heat transfer coefficient at its rear surface affect significantly the temperature distribution and the value of generated thermal emf.

  11. ICRF heating in reactor grade plasmas

    SciTech Connect

    Jacquinot, J.; Bhatnagar, V.P.; Bures, M.; Cottrell, G.A.; Eriksson, L.G.; Sack, C.H.; Start, D.F.H.; Taroni, A. ); Hellsten, T. ); Koch, R. ); Moreau, D. )

    1990-01-01

    Impurity influxes in JET discharges due to ICRH have been reduced to insignificant levels. This has allowed high quality H-modes to be produced with ICRH alone and has enhanced the density limit which is now the same as the NBI limit. Improvement in the deuterium fuel fraction has led to the generation of 100kW of non thermal {sup 3}He-D fusion power. Alpha-particle simulations using MeV ions created by ICRH show classical energy loss and suggest that {alpha}-heating in a reactor will be highly efficient. A clear demonstration of TTMP damping of the fast wave in high beta plasmas has been achieved. A broadband ICRH system is proposed for NET/ITER which will allow fast wave current drive and central ion heating for burn control and ignition. 10 refs., 6 figs.

  12. Finite-volume scheme for anisotropic diffusion

    NASA Astrophysics Data System (ADS)

    van Es, Bram; Koren, Barry; de Blank, Hugo J.

    2016-02-01

    In this paper, we apply a special finite-volume scheme, limited to smooth temperature distributions and Cartesian grids, to test the importance of connectivity of the finite volumes. The area of application is nuclear fusion plasma with field line aligned temperature gradients and extreme anisotropy. We apply the scheme to the anisotropic heat-conduction equation, and compare its results with those of existing finite-volume schemes for anisotropic diffusion. Also, we introduce a general model adaptation of the steady diffusion equation for extremely anisotropic diffusion problems with closed field lines.

  13. Plasma heating for containerless and microgravity materials processing

    NASA Technical Reports Server (NTRS)

    Leung, Emily W. (Inventor); Man, Kin F. (Inventor)

    1994-01-01

    A method for plasma heating of levitated samples to be used in containerless microgravity processing is disclosed. A sample is levitated by electrostatic, electromagnetic, aerodynamic, or acoustic systems, as is appropriate for the physical properties of the particular sample. The sample is heated by a plasma torch at atmospheric pressure. A ground plate is provided to help direct the plasma towards the sample. In addition, Helmholtz coils are provided to produce a magnetic field that can be used to spiral the plasma around the sample. The plasma heating system is oriented such that it does not interfere with the levitation system.

  14. The right circular polarized waves in the three-dimensional anisotropic dispersive photonic crystals consisting of the magnetized plasma and uniaxial material as the Faraday effects considered

    SciTech Connect

    Zhang, Hai-Feng E-mail: lsb@nuaa.edu.cn; Liu, Shao-Bin E-mail: lsb@nuaa.edu.cn; Tang, Yi-Jun; Zhen, Jian-Ping

    2014-03-15

    In this paper, the properties of the right circular polarized (RCP) waves in the three-dimensional (3D) dispersive photonic crystals (PCs) consisting of the magnetized plasma and uniaxial material with face-centered-cubic (fcc) lattices are theoretically investigated by the plane wave expansion method, which the homogeneous anisotropic dielectric spheres (the uniaxial material) immersed in the magnetized plasma background, as the Faraday effects of magnetized plasma are considered (the incidence electromagnetic wave vector is parallel to the external magnetic field at any time). The equations for calculating the anisotropic photonic band gaps (PBGs) for the RCP waves in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and a flatbands region can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, anisotropic dielectric filling factor, plasma frequency, and plasma cyclotron frequency (the external magnetic field) on the properties of first two anisotropic PBGs for the RCP waves are investigated in detail, respectively. The numerical results show that the anisotropy can open partial band gaps in fcc lattices at U and W points, and the complete PBGs for the RCP waves can be achieved compared to the conventional 3D dispersive PCs composed of the magnetized plasma and isotropic material. It is also shown that the first two anisotropic PBGs can be tuned by those parameters as mentioned above. Those PBGs can be enlarged by introducing the uniaxial material into such 3D PCs as the Faraday effects are considered.

  15. 3D Plasma Equilibrium and Stability with Hot Particle Anisotropic Pressure

    SciTech Connect

    Cooper, W. A.; Graves, J. P.; Hirshman, S. P.; Merkel, P.; Kisslinger, J.; Wobig, H. F. G.; Watanabe, K. Y.; Narushima, Y.

    2008-11-01

    The anisotropic pressure free-boundary three-dimsnsional (3D) equilibrium code ANI-MEC with nested magnetic flux surfaces has been developed as an extension of the VMEC2000 code. The preconditioning algorithm included is exploited to allow the computation of equilibrium states with radial force balance error improvements exceeding 4 orders of magnitude compared with the non-conditioned results. Large off-axis energetic particle deposition has been applied in a 2-field period quasiaxisymmetric stellarator reactor at <{beta}>{approx_equal}4.5% to test the limitations of the code. The hot particle pressures are roughly uniform around the flux surfaces when p{sub parallel}>p{sub perpendicular}. The fast particle perpendicular pressures localise in the region of deposition for p{sub perpendicular}>p{sub parallel}, while the energetic particle parallel pressures concentrate on the low-field side. Two anisotropic pressure models for global fluid stability implemented in the TERPSICHORE code have been applied to the LHD Heliotron for a sequence of equilibria with fixed <{beta}{sub dia}>{approx_equal}5%(<{beta}{sub th}>{approx_equal}3.5%) varying the fast particle temperature ratio T{sub parallel}/T{sub perpendicular}. Global magnetohydrodynamic modes are quasi-stable according to the model with rigid hot particle layers, while they become stabilised according to the fully interacting energetic particle model with increasing T{sub parallel}/T{sub perpendicular}. As T{sub parallel}/T{sub perpendicular} approaches 3, however, the n = 1 mode family becomes unstable. A transition from a nearly stable quasi-external ballooning-interchange structure to a weakly unstable internal kink mode takes place. The investigation of beam-driven fusion in a Heliotron system is broached. A background plasma with cold ions and warm electrons at <{beta}{sub ith}>{approx_equal}1% is examined with fixed T{sub parallel}/T{sub perpendicular} = 10 in which the hot particle contribution to <{beta

  16. Theoretical studies on plasma heating and confinement

    SciTech Connect

    Sudan, R.N.

    1993-01-01

    Three principal topics are covered in this final report: Stabilization of low frequency modes of an axisymmetric compact torus plasma confinement system, such as, spheromaks and FRC'S, by a population of large orbit axis encircling energetic ions. Employing an extension of the energy principle' which utilizes a Vlasov description for the energetic 'ion component, it has been demonstrated that short wavelength MHD type modes are stabilized while the long wavelength tilt and precessional modes are marginally stable. The deformation of the equilibrium configuration by the energetic ions results in the stabilization of the tilt mode for spheromaks. Formation of Ion Rings and their coalescence with spheromaks. A two dimensional electromagnetic PIC codes has been developed for the study of ion ring formation and its propagation, deformation and slowing down in a cold plasma. It has been shown that a ring moving at a speed less than the Alfven velocity can merge with a stationary spheromak. Anomalous transport from drift waves in a Tokomak. The Direct Interaction Approximation in used to obtain incremental transport coefficients for particles and heat for drift waves in a Tokomak. It is shown that the transport matrix does not obey Onsager's principle.

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

    DOEpatents

    Coppi, B.; Montgomery, D.B.

    1973-12-11

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

  18. Anisotropic Mechanical Properties of Plasma-Sprayed Thermal Barrier Coatings at High Temperature Determined by Ultrasonic Method

    NASA Astrophysics Data System (ADS)

    Wei, Qin; Zhu, Jianguo; Chen, Wei

    2016-02-01

    The mechanical properties of plasma-sprayed thermal barrier coatings (TBC) are of great scientific and technological significance for the design and fabrication of TBC systems. The ultrasonic method combined with a sing-around method for mechanical properties measurement of TBC is deduced and the elastic modulus can be determined in the spray, or longitudinal, direction, and the transverse direction. Tested specimens of plasma-sprayed TBC are detached from the substrate and treated with thermal exposure at 1400 °C. The elastic moduli along the longitudinal and transverse directions of the TBCs are measured by different types of ultrasonic waves combined with a sing-around method, while the Poisson's ratio is also obtained simultaneously. The experimental results indicate that the magnitude of longitudinal elastic modulus is larger than that of the transverse one, and thus the plasma-sprayed TBC has an anisotropic mechanical property. Moreover, the elastic moduli along both longitudinal and transverse directions change with high-temperature exposure time, which consists of a rapid increasing stage followed by a slow decreasing stage. In addition, the magnitude of Poisson's ratio increases slightly from 0.05 to 0.2 with the high-temperature exposure time. Generally, the microstructures in the plasma-sprayed coatings and their evolution in a high-temperature environment are the main causes of the varying anisotropic mechanical properties.

  19. An anisotropic character of nonlinear fluxes not involved in the plasma energy transport in the Hasegawa-Wakatani model

    NASA Astrophysics Data System (ADS)

    Min, Byunghoon; An, Chan-Yong; Kim, Chang-Bae; Lee, Gun Bok

    2015-04-01

    Fluxes of both the vorticity and the plasma density due to the nonlinear E × B convective derivatives are divided into two parts. One part, which is almost isotropic, is well known to engage in the transfer of energies from the energy-producing scale where the phase mismatch between the density and the electric potential is large. The other part, in the Fourier space , is found to be highly anisotropic. If it is summed over k y , the result is nearly random around zero in k x while the sum over k x is approximately proportional to k y . In Fourier space, such anisotropic fluxes are found to be closely related to the gradients of the squares of the vorticity and the electric potential, respectively. We argue that the advecting velocities in Fourier space may be predicted on dimensional grounds.

  20. Full-wave Simulations of ICRF Heating in Toroidal Plasma with Non-Maxwellian Distribution Functions in the FLR Limit

    SciTech Connect

    E.J. Valeo, C.K. Phillips, H. Okuda, J.C. Wright, P.T. Bonoli, L.A. Berry, and the RF SciDAC Team

    2007-07-18

    At the power levels required for signicant heating and current drive in magnetically-con ned toroidal plasma, modi cation of the particle distribution function from a Maxwellian shape is likely [T.H. Stix, Nucl. Fusion, 15:737 1975], with consequent changes in wave propagation and in the location and amount of absorption. In order to study these e ects computationally, the nite-Larmor-radius, full-wave, hot-plasma toroidal simulation code, TORIC [M. Brambilla. Plasma Phys. Controlled Fusion, 41:1, 1999], has been extended to allow the prescription of arbitrary velocity distributions of the form ƒ (ν||, ν⊥, Ψ, θ). For H minority heating of a D-H plasma with anisotropic Maxwellian H distributions, the fractional H absorption varies signi cantly with changes in parallel temperature but is essentially independent of perpendicular temperature.

  1. Plasma heating via adiabatic magnetic compression-expansion cycle

    NASA Astrophysics Data System (ADS)

    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.

  2. Ion cyclotron heating experiments in magnetosphere plasma device RT-1

    SciTech Connect

    Nishiura, M. Yoshida, Z.; Yano, Y.; Kawazura, Y.; Saitoh, H.; Yamasaki, M.; Mushiake, T.; Kashyap, A.; Takahashi, N.; Nakatsuka, M.; Fukuyama, A.

    2015-12-10

    The ion cyclotron range of frequencies (ICRF) heating with 3 MHz and ∼10 kW is being prepared in RT-1. The operation regime for electron cyclotron resonance (ECR) heating is surveyed as the target plasmas. ECRH with 8.2 GHz and ∼50 kW produces the plasmas with high energy electrons in the range of a few ten keV, but the ions still remain cold at a few ten eV. Ion heating is expected to access high ion beta state and to change the aspect of plasma confinement theoretically. The ICRF heating is applied to the target plasma as an auxiliary heating. The preliminary result of ICRF heating is reported.

  3. Instability of field-aligned electron-cyclotron waves in a magnetic mirror plasma with anisotropic temperature

    NASA Astrophysics Data System (ADS)

    Grishanov, N. I.; Azarenkov, N. A.

    2016-08-01

    > Dispersion characteristics have been analysed for field-aligned electron-cyclotron waves (also known as right-hand polarized waves, extraordinary waves or whistlers) in a cylindrical magnetic mirror plasma including electrons with anisotropic temperature. It is shown that the instability of these waves is possible only in the range below the minimal electron-cyclotron frequency, which is much lower than the gyrotron frequency used for electron-cyclotron resonance power input into the plasma, under the condition where the perpendicular temperature of the resonant electrons is larger than their parallel temperature. The growth rates of whistler instability in the two magnetized plasma models, where the stationary magnetic field is either uniform or has a non-uniform magnetic mirror configuration, are compared.

  4. Two-Dimensional Hybrid Models of Inhomogeneous Expanding Solar Wind Plasma Heating by Turbulent Wave Spectrum

    NASA Astrophysics Data System (ADS)

    Ozak, N.; Ofman, L.; Vinas, A. F.; Maneva, Y. G.

    2013-12-01

    Remote sensing observations of solar wind plasma show that heavy ions are hotter than protons and that their temperature is anisotropic. In-situ observations of fast solar wind streams at distances of 0.29 AU and beyond by Helios and recently at ~1 AU by STEREO, ACE, and Wind spacecraft provide direct evidence for the presence of turbulent Alfven wave spectrum and of left-hand polarized ion-cyclotron waves in the coronal plasma. The latter can produce temperature anisotropies by resonant absorption and perpendicular heating of the ions. Furthermore, measurements indicate that Ti,⊥>>Ti,‖, contrary to what is expected in purely adiabatic expansion of the solar wind plasma, which predicts the opposite effect due to conservation of magnetic moment of the expanding ions. Future Solar Probe+ mission will provide in-situ observations of solar wind plasma close to the Sun where it is expected to be inhomogeneous on small scales. Here, we study the heating and the acceleration of solar wind ions (H+, He++) in inhomogeneous plasma with a turbulent spectrum of Alfvénic fluctuations using 2.5D hybrid code. The 2-D model allows us to explore inhomogeneities in the plasma and obliquely propagating waves. We extend previous work (Ofman 2010; Ofman et al. 2011) by including the expansion of the solar wind and study its effect on the perpendicular ion heating and cooling, and on the spectrum of the magnetic fluctuations in the inhomogeneous background wind. We also study the effects of inhomogeneous drift on the heating of the ions. We compare our results to the available observations.

  5. Viscous effects on motion and heating of electrons in inductively coupled plasma reactors

    SciTech Connect

    Chang, C.H.; Bose, D.

    1999-10-01

    A transport model is developed for nonlocal effects on motion and heating of electrons in inductively coupled plasma reactors. The model is based on the electron momentum equation derived from the Boltzmann equation, retaining anisotropic stress components which in fact are viscous stresses. The resulting model consists of transport equations for the magnitude of electron velocity oscillation and terms representing energy dissipation due to viscous stresses in the electron energy equation. In this model, electrical current is obtained in a nonlocal manner due to viscous effects, instead of Ohm's law or the electron momentum equation without viscous effects, while nonlocal heating of electrons is represented by the viscous dissipation. Computational results obtained by two-dimensional numerical simulations show that nonlocal determination of electrical current indeed is important, and viscous dissipation becomes an important electron heating mechanism at low pressures. It is suspected that viscous dissipation in inductively coupled plasma reactors in fact represents stochastic heating of electrons, and this possibility is exploited by discussing physical similarities between stochastic heating and energy dissipation due to the stress tensor.

  6. The Voigt effects in the anisotropic photonic band gaps of three-dimensional magnetized plasma photonic crystals doped by the uniaxial material

    NASA Astrophysics Data System (ADS)

    Zhang, Hai-Feng; Liu, Shao-Bin; Li, Bing-Xiang

    2013-10-01

    In this paper, the properties of photonic band gaps (PBGs) for three-dimensional magnetized plasma photonic crystals (MPPCs) composed of anisotropic dielectric (the uniaxial material) spheres immersed in homogeneous magnetized plasma background with simple-cubic lattices are theoretically investigated by the plane wave expansion (PWE) method, as the Voigt effects of magnetized plasma are considered. The equations for calculating the anisotropic PBGs in the first irreducible Brillouin zone are theoretically deduced. The anisotropic PBGs and two flatband regions can be obtained. The effects of the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency and plasma cyclotron frequency on the characteristics of anisotropic PBGs for the three-dimensional MPPCs are studied in detail and some corresponding physical explanations are also given. The numerical results show that the anisotropy can open partial band gaps in simple-cubic lattices and the complete PBGs can be found compared to the conventional three-dimensional MPPCs doped by the isotropic material. The bandwidths of PBGs can be enlarged by introducing the magnetized plasma into three-dimensional PCs containing the uniaxial material. It is also shown that the anisotropic PBGs can be manipulated by the ordinary-refractive index, extraordinary-refractive index, filling factor, plasma frequency and plasma cyclotron frequency. The locations of flatband regions cannot be tuned by any parameters except for the plasma frequency and plasma cyclotron frequency. Introducing the uniaxial material in three-dimensional magnetized plasma-dielectric photonic crystals can enlarge the PBGs and also provide a way to obtain the complete PBGs as the three-dimensional MPPCs with high symmetry.

  7. Strongly-coupled plasmas formed from laser-heated solids

    PubMed Central

    Lyon, M.; Bergeson, S. D.; Hart, G.; Murillo, M. S.

    2015-01-01

    We present an analysis of ion temperatures in laser-produced plasmas formed from solids with different initial lattice structures. We show that the equilibrium ion temperature is limited by a mismatch between the initial crystallographic configuration and the close-packed configuration of a strongly-coupled plasma, similar to experiments in ultracold neutral plasmas. We propose experiments to demonstrate and exploit this crystallographic heating in order to produce a strongly coupled plasma with a coupling parameter of several hundred. PMID:26503293

  8. Strongly-coupled plasmas formed from laser-heated solids.

    PubMed

    Lyon, M; Bergeson, S D; Hart, G; Murillo, M S

    2015-01-01

    We present an analysis of ion temperatures in laser-produced plasmas formed from solids with different initial lattice structures. We show that the equilibrium ion temperature is limited by a mismatch between the initial crystallographic configuration and the close-packed configuration of a strongly-coupled plasma, similar to experiments in ultracold neutral plasmas. We propose experiments to demonstrate and exploit this crystallographic heating in order to produce a strongly coupled plasma with a coupling parameter of several hundred. PMID:26503293

  9. Turbulence and Proton–Electron Heating in Kinetic Plasma

    NASA Astrophysics Data System (ADS)

    Matthaeus, William H.; Parashar, Tulasi N.; Wan, Minping; Wu, P.

    2016-08-01

    Analysis of particle-in-cell simulations of kinetic plasma turbulence reveals a connection between the strength of cascade, the total heating rate, and the partitioning of dissipated energy into proton heating and electron heating. A von Karman scaling of the cascade rate explains the total heating across several families of simulations. The proton to electron heating ratio increases in proportion to total heating. We argue that the ratio of gyroperiod to nonlinear turnover time at the ion kinetic scales controls the ratio of proton and electron heating. The proposed scaling is consistent with simulations.

  10. Alpha Heating and Burning Plasmas in Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Betti, R.; Christopherson, A. R.; Spears, B. K.; Nora, R.; Bose, A.; Howard, J.; Woo, K. M.; Edwards, M. J.; Sanz, J.

    2015-06-01

    Estimating the level of alpha heating and determining the onset of the burning plasma regime is essential to finding the path towards thermonuclear ignition. In a burning plasma, the alpha heating exceeds the external input energy to the plasma. Using a simple model of the implosion, it is shown that a general relation can be derived, connecting the burning plasma regime to the yield enhancement due to alpha heating and to experimentally measurable parameters such as the Lawson ignition parameter. A general alpha-heating curve is found, independent of the target and suitable to assess the performance of all laser fusion experiments whether direct or indirect drive. The onset of the burning plasma regime inside the hot spot of current implosions on the National Ignition Facility requires a fusion yield of about 50 kJ.

  11. Alpha Heating and Burning Plasmas in Inertial Confinement Fusion.

    PubMed

    Betti, R; Christopherson, A R; Spears, B K; Nora, R; Bose, A; Howard, J; Woo, K M; Edwards, M J; Sanz, J

    2015-06-26

    Estimating the level of alpha heating and determining the onset of the burning plasma regime is essential to finding the path towards thermonuclear ignition. In a burning plasma, the alpha heating exceeds the external input energy to the plasma. Using a simple model of the implosion, it is shown that a general relation can be derived, connecting the burning plasma regime to the yield enhancement due to alpha heating and to experimentally measurable parameters such as the Lawson ignition parameter. A general alpha-heating curve is found, independent of the target and suitable to assess the performance of all laser fusion experiments whether direct or indirect drive. The onset of the burning plasma regime inside the hot spot of current implosions on the National Ignition Facility requires a fusion yield of about 50 kJ. PMID:26197131

  12. Alpha heating and burning plasmas in inertial confinement fusion

    SciTech Connect

    Betti, R.; Christopherson, A. R.; Spears, B. K.; Nora, R.; Bose, A.; Howard, J.; Woo, K. M.; Edwards, M. J.; Sanz, J.

    2015-06-01

    Estimating the level of alpha heating and determining the onset of the burning plasma regime is essential to finding the path towards thermonuclear ignition. In a burning plasma, the alpha heating exceeds the external input energy to the plasma. Using a simple model of the implosion, it is shown that a general relation can be derived, connecting the burning plasma regime to the yield enhancement due to alpha heating and to experimentally measurable parameters such as the Lawson ignition parameter. A general alpha-heating curve is found, independent of the target and suitable to assess the performance of all laser fusion experiments whether direct or indirect drive. The onset of the burning plasma regime inside the hot spot of current implosions on the National Ignition Facility requires a fusion yield of about 50 kJ.

  13. Further testing of anisotropic plasma turbulence theory with spacecraft observations of the solar wind

    NASA Astrophysics Data System (ADS)

    Summerlin, E. J.; Wicks, R.; Forman, M. A.; Salem, C. S.; Roberts, D. A.

    2014-12-01

    We use magnetic field observations from the fast solar wind made by the Ulysses, Wind, and Cluster spacecraft to measure the anisotropic scaling of the full power-spectra-tensor of inertial range turbulence in the solar wind. We use the results to make the most rigorous test of anisotropic turbulence theories thus far by solar wind observations. We compare the diagonal and off-diagonal terms of the tensor at different scales to reveal the different effects of sampling causing the projection of the anisotropic spectrum into the spacecraft observation frame. There is clear indication of anisotropy similar to "critical balance" in the inertial range, but the most striking result is the departure from the inertial range behavior observed at smaller scales in the "dissipation range".

  14. Plasma heating and hot ion sustaining in mirror based hybrids

    SciTech Connect

    Moiseenko, V. E.; Agren, O.

    2012-06-19

    Possibilities of plasma heating and sloshing ion sustaining in mirror based hybrids are briefly reviewed. Sloshing ions, i.e. energetic ions with a velocity distribution concentrated to a certain pitch-angle, play an important role in plasma confinement and generation of fusion neutrons in mirror machines. Neutral beam injection (NBI) is first discussed as a method to generate sloshing ions. Numerical results of NBI modeling for a stellarator-mirror hybrid are analyzed. The sloshing ions could alternatively be sustained by RF heating. Fast wave heating schemes, i.e. magnetic beach, minority and second harmonic heating, are addressed and their similarities and differences are described. Characteristic features of wave propagation in mirror hybrid devices including both fundamental harmonic minority and second harmonic heating are examined. Minority heating is efficient for a wide range of minority concentration and plasma densities; it allows one to place the antenna aside from the hot ion location. A simple-design strap antenna suitable for this has good performance. However, this scenario is appropriate only for light minority ions. The second harmonic heating can be applied for the heavy ion component. Arrangements are similar for minority and second harmonic heating. The efficiency of second harmonic heating is influenced by a weaker wave damping than for minority heating. Numerical calculations show that in a hybrid reactor scaled mirror machine the deuterium sloshing ions could be heated within the minority heating scheme, while the tritium ions could be sustained by second harmonic heating.

  15. ICRF Heated Long-Pulse Plasma Discharges in LHD

    NASA Astrophysics Data System (ADS)

    Kumazawa, R.; Seki, T.; Mutoh, T.; Saito, K.; Watari, T.; Nakamura, Y.; Sakamoto, M.; Watanabe, T.; Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takeiri, Y.; Oka, Y.; Tsumori, K.; Osakabe, M.; Ikeda, K.; Nagaoka, K.; Kaneko, O.; Miyazawa, J.; Morita, S.; Narihara, K.; Shoji, M.; Masuzaki, S.; Goto, M.; Morisaki, T.; Peterson, B. J.; Sato, K.; Tokuzawa, T.; Ashikawa, N.; Nishimura, K.; Funaba, H.; Chikaraishi, H.; Notake, T.; Torii, Y.; Okada, H.; Ichimura, M.; Higaki, H.; Takase, Y.; Kasahara, H.; Shimpo, F.; Nomura, G.; Takahashi, C.; Yokota, M.; Kato, A.; Zhao, Yanping; Yoon, J. S.; Kwak, J. G.; Yamada, H.; Kawahata, K.; Ohyabu, N.; Ida, K.; Nagayama, Y.; Noda, N.; Komori, A.; Sudo, S.; Motojima, O.; LHD Experimental Group

    2006-01-01

    A long-pulse plasma discharge for more than 30 min. was achieved on the Large Helical Device (LHD). A plasma of ne = 0.8× 1019 m-3 and Ti0 = 2.0 keV was sustained with PICH = 0.52 MW, PECH = 0.1 MW and averaged PNBI = 0.067 MW. Total injected heating energy was 1.3 GJ, which was a quarter of the prepared RF heating energy. One of the keys to the success of the experiment was a dispersion of the local plasma heat load to divertors, accomplished by shifting the magnetic axis inward and outward.

  16. Heating and cooling of the earth's plasma sheet

    NASA Technical Reports Server (NTRS)

    Goertz, C. K.

    1990-01-01

    Magnetic-field models based on pressure equilibrium in the quiet magnetotail require nonadiabatic cooling of the plasma as it convects inward or a decrease of the flux tube content. Recent in situ observations of plasma density and temperature indicate that, during quiet convection, the flux tube content may actually increase. Thus the plasma must be cooled during quiet times. The earth plasma sheet is generally significantly hotter after the expansion phase of a substorm than before the plasma sheet thinning begins and cools during the recovery phase. Heating mechanisms such as reconnection, current sheet acceleration, plasma expansion, and resonant absorption of surface waves are discussed. It seems that all mechanisms are active, albeit in different regions of the plasma sheet. Near-earth tail signatures of substorms require local heating as well as a decrease of the flux tube content. It is shown that the resonant absorption of surface waves can provide both.

  17. Graphics processing unit (GPU)-based computation of heat conduction in thermally anisotropic solids

    NASA Astrophysics Data System (ADS)

    Nahas, C. A.; Balasubramaniam, Krishnan; Rajagopal, Prabhu

    2013-01-01

    Numerical modeling of anisotropic media is a computationally intensive task since it brings additional complexity to the field problem in such a way that the physical properties are different in different directions. Largely used in the aerospace industry because of their lightweight nature, composite materials are a very good example of thermally anisotropic media. With advancements in video gaming technology, parallel processors are much cheaper today and accessibility to higher-end graphical processing devices has increased dramatically over the past couple of years. Since these massively parallel GPUs are very good in handling floating point arithmetic, they provide a new platform for engineers and scientists to accelerate their numerical models using commodity hardware. In this paper we implement a parallel finite difference model of thermal diffusion through anisotropic media using the NVIDIA CUDA (Compute Unified device Architecture). We use the NVIDIA GeForce GTX 560 Ti as our primary computing device which consists of 384 CUDA cores clocked at 1645 MHz with a standard desktop pc as the host platform. We compare the results from standard CPU implementation for its accuracy and speed and draw implications for simulation using the GPU paradigm.

  18. Impact of Gas Heating in Inductively Coupled Plasmas

    NASA Technical Reports Server (NTRS)

    Hash, D. B.; Bose, D.; Rao, M. V. V. S.; Cruden, B. A.; Meyyappan, M.; Sharma, S. P.; Biegel, Bryan (Technical Monitor)

    2001-01-01

    Recently it has been recognized that the neutral gas in inductively coupled plasma reactors heats up significantly during processing. The resulting gas density variations across the reactor affect reaction rates, radical densities, plasma characteristics, and uniformity within the reactor. A self-consistent model that couples the plasma generation and transport to the gas flow and heating has been developed and used to study CF4 discharges. A Langmuir probe has been used to measure radial profiles of electron density and temperature. The model predictions agree well with the experimental results. As a result of these comparisons along with the poorer performance of the model without the gas-plasma coupling, the importance of gas heating in plasma processing has been verified.

  19. Resonant-cavity antenna for plasma heating

    DOEpatents

    Perkins, Jr., Francis W.; Chiu, Shiu-Chu; Parks, Paul; Rawls, John M.

    1987-01-01

    Disclosed is a resonant coil cavity wave launcher for energizing a plasma immersed in a magnetic field. Energization includes launching fast Alfven waves to excite ion cyclotron frequency resonances in the plasma. The cavity includes inductive and capacitive reactive members spaced no further than one-quarter wavelength from a first wall confinement chamber of the plasma. The cavity wave launcher is energized by connection to a waveguide or transmission line carrying forward power from a remote radio frequency energy source.

  20. Direct heating of imploded plasma in the fast ignition

    NASA Astrophysics Data System (ADS)

    Sunahara, Atsushi; Johzaki, Tomoyuki; Nagatomo, Hideo; Mima, Kunioki; Shiraga, Hiroyuki; Azechi, Hiroshi; Mori, Yohitaga; Kitagawa, Yoneyoshi

    2016-03-01

    We propose the direct heating of an imploded plasma core by ultra-intense lasers in inertial confinement fusion, to increase the heating coupling efficiency. In this scheme, both fast-electrons and fast-ions heat the plasma core. Experiments using this direct heating scheme has been carried out at GXII and LFEX laser facility at Osaka Univeristy. To model this direct heating scheme, we developed the 1D simulation model and carried out simulations using the experimental conditions. Comparison between results of the simulation and the experimental observations validates the simulation model. We show that even in the unoptimized experimental conditions used in simulations, our calculations show that the maximum temperature, 1.6 keV, of the CD plasma.

  1. Plasma Heating and Flow in an Auroral Arc

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Chandler, M. O.; Pollock, C. J.; Reasoner, D. L.; Arnoldy, R. L.; Austin, B.; Kintner, P. M.; Bonnell, J.

    1996-01-01

    We report direct observations of the three-dimensional velocity distribution of selected topside ionospheric ion species in an auroral context between 500 and 550 km altitude. We find heating transverse to the local magnetic field in the core plasma, with significant heating of 0(+), He(+), and H(+), as well as tail heating events that occur independently of the core heating. The 0(+) velocity distribution departs from bi-Maxwellian, at one point exhibiting an apparent ring-like shape. However, these observations are shown to be aliased within the auroral arc by temporal variations that arc not well-resolved by the core plasma instrument. The dc electric field measurements reveal superthermal plasma drifts that are consistent with passage of the payload through a series of vortex structures or a larger scale circularly polarized hydromagnetic wave structure within the auroral arc. The dc electric field also shows that impulsive solitary structures, with a frequency spectrum in the ion cyclotron frequency range, occur in close correlation with the tail heating events. The drift and core heating observations lend support to the idea that core ion heating is driven at low altitudes by rapid convective motions imposed by the magnetosphere. Plasma wave emissions at ion frequencies and parallel heating of the low-energy electron plasma are observed in conjunction with this auroral form; however, the conditions are much more complex than those typically invoked in previous theoretical treatments of superthermal frictional heating. The observed ion heating within the arc clearly exceeds that expected from frictional heating for the light ion species H(+) and He(+), and the core distributions also contain hot transverse tails, indicating an anomalous transverse heat source.

  2. Axial laser heating of three meter theta pinch plasma columns

    NASA Astrophysics Data System (ADS)

    Hoffman, A. L.; Lowenthal, D. D.

    1980-10-01

    A 3-m long plasma column formed and confined by a fast rising solenoidal field was irradiated from one end by a powerful pulsed CO2 laser. It was found that beam trapping density minima could be maintained for the length of the laser pulse if the plasma diameter exceeded about 1.5 cm. The erosion of the density minimum was governed by classical diffusion processes. Three meter long plasmas in 2.6 cm bore plasma tubes could be fairly uniformly heated by 3.0 kJ of CO2 laser irradiation. Best results were obtained when heating began before or during the theta pinch implosion phase and the plasma fill pressure exceeded 1.0 torr H2. Plasma line energies of about 1 kJ/m could be obtained in a magnetic field rising to 6 T in 4.7 microseconds.

  3. Confinement and heating of a deuterium-tritium plasma

    SciTech Connect

    Hawryluk, R. J.; Adler, H.; Alling, P.; Synakowski, E.

    1994-03-01

    The Tokamak Fusion Test Reactor (TFTR) has performed initial high-power experiments with the plasma fueled by deuterium and tritium to nominally equal densities. Compared to pure deuterium plasmas, the energy stored in the electron and ions increased by ~20%. These increases indicate improvements in confinement associated with the use of tritium and possibly heating of electrons by α-particles.

  4. Properties of radio-frequency heated argon confined uranium plasmas

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Pure uranium hexafluoride (UF6) was injected into an argon confined, steady state, rf-heated plasma within a fused silica peripheral wall test chamber. Exploratory tests conducted using an 80 kW rf facility and different test chamber flow configurations permitted selection of the configuration demonstrating the best confinement characteristics and minimum uranium compound wall coating. The overall test results demonstrated applicable flow schemes and associated diagnostic techniques were developed for the fluid mechanical confinement and characterization of uranium within an rf plasma discharge when pure UF6 is injected for long test times into an argon-confined, high-temperature, high-pressure, rf-heated plasma.

  5. Plasma Heating Simulation in the VASIMR System

    NASA Technical Reports Server (NTRS)

    Ilin, Andrew V.; ChangDiaz, Franklin R.; Squire, Jared P.; Carter, Mark D.

    2005-01-01

    The paper describes the recent development in the simulation of the ion-cyclotron acceleration of the plasma in the VASIMR experiment. The modeling is done using an improved EMIR code for RF field calculation together with particle trajectory code for plasma transport calculat ion. The simulation results correlate with experimental data on the p lasma loading and predict higher ICRH performance for a higher density plasma target. These simulations assist in optimizing the ICRF anten na so as to achieve higher VASIMR efficiency.

  6. Anisotropic Thermal Diffusion

    NASA Astrophysics Data System (ADS)

    Gardiner, Thomas

    2013-10-01

    Anisotropic thermal diffusion in magnetized plasmas is an important physical phenomena for a diverse set of physical conditions ranging from astrophysical plasmas to MFE and ICF. Yet numerically simulating this phenomenon accurately poses significant challenges when the computational mesh is misaligned with respect to the magnetic field. Particularly when the temperature gradients are unresolved, one frequently finds entropy violating solutions with heat flowing from cold to hot zones for χ∥ /χ⊥ >=102 which is substantially smaller than the range of interest which can reach 1010 or higher. In this talk we present a new implicit algorithm for solving the anisotropic thermal diffusion equations and demonstrate its characteristics on what has become a fairly standard set of test problems in the literature. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2013-5687A.

  7. Neutral beam heating of detached plasmas in TFTR

    SciTech Connect

    Bush, C.E.; Strachan, J.D.; Schivell, J.; Mansfield, D.K.; Taylor, G.; Grek, B.; Budny, R.; McNeill, D.H.; Bell, M.G.; Boody, F.P.

    1989-05-01

    Detached plasmas on TFTR have been heated with neutral beam auxiliary power for the first time. At beam powers above 2 MW the detached plasmas in TFTR expand and reattach to the limiters. Deuterium and/or impurity gas puffing can be used to maintain plasmas in the detached state at powers of over 5 MW. Transient events were observed in a number of these plasmas, including a confinement-related delay in evolution of the edge emissivity and some phenomena which appear similar to those seen in the H-mode. 16 refs., 5 figs.

  8. Plasma-assisted synthesis and high-resolution characterization of anisotropic elemental and bimetallic core–shell magnetic nanoparticles

    PubMed Central

    Lotnyk, A

    2014-01-01

    Summary Magnetically anisotropic as well as magnetic core–shell nanoparticles (CS-NPs) with controllable properties are highly desirable in a broad range of applications. With this background, a setup for the synthesis of heterostructured magnetic core–shell nanoparticles, which relies on (optionally pulsed) DC plasma gas condensation has been developed. We demonstrate the synthesis of elemental nickel nanoparticles with highly tunable sizes and shapes and Ni@Cu CS-NPs with an average shell thickness of 10 nm as determined with scanning electron microscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy measurements. An analytical model that relies on classical kinetic gas theory is used to describe the deposition of Cu shell atoms on top of existing Ni cores. Its predictive power and possible implications for the growth of heterostructured NP in gas condensation processes are discussed. PMID:24778973

  9. Plasma Heating and Sustainment with ICRH on W7AS

    NASA Astrophysics Data System (ADS)

    Cattanei, G.; Hartmann, D. A.; Lyon, J. F.

    1996-11-01

    Ion cyclotron resonance heating (ICRH) has successfully been demonstrated on the W7AS stellarator. A novel antenna, located on the high-field side of the torus, was designed to excite a narrow spectrum of k_allel≈ 6 m-1 fast waves. About 80% of the power radiated from the antenna was accounted for in the plasma. No significant increase in the impurity content of the plasma was observed. In second harmonic heating the diamagnetic energy W_dia increased about 10% (0.6 kJ). For H-minority heating of an ECRH deuterium target plasma (H/D ≈ 10%), W_dia increased about 15% (1 kJ) and T_D(0) rose from 300 eV to 400 eV. With H-minority heating it was possible to sustain an ECRH-created plasma with ICRH alone. The duration was limited solely by arcing in the transmission lines or antenna feeds. A steady state condition was obtained about 200 msec into the ICRH-only phase of the discharge. Typical parameters were W_dia = 2 kJ, ≈ 4×10^19 m-3, T_e(0) = 300 eV, and T_D(0) = 350 eV. The plasma profile was narrower and had steeper edges than in comparable ECRH plasmas.

  10. Plasma β Scaling of Anisotropic Magnetic Field Fluctuations in the Solar Wind Flux Tube

    NASA Astrophysics Data System (ADS)

    Sarkar, Aveek; Bhattacharjee, Amitava; Ebrahimi, Fatima

    2014-03-01

    Based on various observations, it has been suggested that at 1 AU, solar wind consists of "spaghetti"-like magnetic field structures that have the magnetic topology of flux tubes. It is also observed that the plasma fluctuation spectra at 1 AU show a plasma β dependence. Reconciling these two sets of observations and using the Invariance Principle, Bhattacharjee et al. suggested that the plasma inside every flux tube may become unstable with respect to pressure-driven instabilities and gives rise to fluctuation spectra that depend on the local plasma β. The present work is the first direct numerical simulation of such a flux tube. We solve the full magnetohydrodynamic equations using the DEBS code and show that if the plasma inside the flux tube is driven unstable by spatial inhomogeneities in the background plasma pressure, the observed nature of the fluctuating power spectra agrees reasonably well with observations, as well as the analytical prediction of Bhattacharjee et al.

  11. Plasma β scaling of anisotropic magnetic field fluctuations in the solar wind flux tube

    SciTech Connect

    Sarkar, Aveek; Bhattacharjee, Amitava; Ebrahimi, Fatima E-mail: amitava@princeton.edu

    2014-03-10

    Based on various observations, it has been suggested that at 1 AU, solar wind consists of 'spaghetti'-like magnetic field structures that have the magnetic topology of flux tubes. It is also observed that the plasma fluctuation spectra at 1 AU show a plasma β dependence. Reconciling these two sets of observations and using the Invariance Principle, Bhattacharjee et al. suggested that the plasma inside every flux tube may become unstable with respect to pressure-driven instabilities and gives rise to fluctuation spectra that depend on the local plasma β. The present work is the first direct numerical simulation of such a flux tube. We solve the full magnetohydrodynamic equations using the DEBS code and show that if the plasma inside the flux tube is driven unstable by spatial inhomogeneities in the background plasma pressure, the observed nature of the fluctuating power spectra agrees reasonably well with observations, as well as the analytical prediction of Bhattacharjee et al.

  12. Local thermodynamic equilibrium in rapidly heated high energy density plasmas

    SciTech Connect

    Aslanyan, V.; Tallents, G. J.

    2014-06-15

    Emission spectra and the dynamics of high energy density plasmas created by optical and Free Electron Lasers (FELs) depend on the populations of atomic levels. Calculations of plasma emission and ionization may be simplified by assuming Local Thermodynamic Equilibrium (LTE), where populations are given by the Saha-Boltzmann equation. LTE can be achieved at high densities when collisional processes are much more significant than radiative processes, but may not be valid if plasma conditions change rapidly. A collisional-radiative model has been used to calculate the times taken by carbon and iron plasmas to reach LTE at varying densities and heating rates. The effect of different energy deposition methods, as well as Ionization Potential Depression are explored. This work shows regimes in rapidly changing plasmas, such as those created by optical lasers and FELs, where the use of LTE is justified, because timescales for plasma changes are significantly longer than the times needed to achieve an LTE ionization balance.

  13. Local thermodynamic equilibrium in rapidly heated high energy density plasmas

    NASA Astrophysics Data System (ADS)

    Aslanyan, V.; Tallents, G. J.

    2014-06-01

    Emission spectra and the dynamics of high energy density plasmas created by optical and Free Electron Lasers (FELs) depend on the populations of atomic levels. Calculations of plasma emission and ionization may be simplified by assuming Local Thermodynamic Equilibrium (LTE), where populations are given by the Saha-Boltzmann equation. LTE can be achieved at high densities when collisional processes are much more significant than radiative processes, but may not be valid if plasma conditions change rapidly. A collisional-radiative model has been used to calculate the times taken by carbon and iron plasmas to reach LTE at varying densities and heating rates. The effect of different energy deposition methods, as well as Ionization Potential Depression are explored. This work shows regimes in rapidly changing plasmas, such as those created by optical lasers and FELs, where the use of LTE is justified, because timescales for plasma changes are significantly longer than the times needed to achieve an LTE ionization balance.

  14. Heat sink effects in variable polarity plasma arc welding

    NASA Technical Reports Server (NTRS)

    Abdelmessih, Amanie N.

    1991-01-01

    The Space Shuttle External Tank is fabricated by the variable polarity plasma arc (VPPA) welding process. In VPPA welding, a noble gas, usually argon, is directed through an arc to emerge from the torch as a hot plasma jet. This jet is surrounded by a shielding gas, usually helium, to protect the weld from contamination with air. The high velocity, hot plasma jet completely penetrates the workpiece (resembling a line heat source) when operated in the 'keyhole' mode. The metal melts on touching the side of the jet, as the torch travels in the perpendicular direction to the direction of the jet, and melted metal moves around the plasma jet in the keyhole forming a puddle which solidifies behind the jet. Heat sink effects are observed when there are irregularities in the workpiece configuration, especially, if these irregularities are close to the weld bead. These heat sinks affect the geometry of the weld bead, i.e., in extreme cases they could cause defects such as incomplete fusion. Also, different fixtures seem to have varying heat sink effects. The objective of this research is to study the effect of irregularities in workpiece configuration and fixture differences (heat sink effects) on the weld bead geometry with the ultimate objective to compensate for the heat sink effects and achieve a perfect weld. Experiments were performed on different workpiece geometries and compared to approximate models.

  15. Plasma rotation and rf heating in DIII-D

    SciTech Connect

    deGrassie, J.S.; Baker, D.R.; Burrell, K.H.

    1999-05-01

    In a variety of discharge conditions on DIII-D it is observed that rf electron heating reduces the toroidal rotation speed and core ion temperature. The rf heating can be with either fast wave or electron cyclotron heating and this effect is insensitive to the details of the launched toroidal wavenumber spectrum. To date all target discharges have rotation first established with co-directed neutral beam injection. A possible cause is enhanced ion momentum and thermal diffusivity due to electron heating effectively creating greater anomalous viscosity. Another is that a counter directed toroidal force is applied to the bulk plasma via rf driven radial current.

  16. High-frequency plasma-heating apparatus

    DOEpatents

    Brambilla, Marco; Lallia, Pascal

    1978-01-01

    An array of adjacent wave guides feed high-frequency energy into a vacuum chamber in which a toroidal plasma is confined by a magnetic field, the wave guide array being located between two toroidal current windings. Waves are excited in the wave guide at a frequency substantially equal to the lower frequency hybrid wave of the plasma and a substantially equal phase shift is provided from one guide to the next between the waves therein. For plasmas of low peripheral density gradient, the guides are excited in the TE.sub.01 mode and the output electric field is parallel to the direction of the toroidal magnetic field. For exciting waves in plasmas of high peripheral density gradient, the guides are excited in the TM.sub.01 mode and the magnetic field at the wave guide outlets is parallel to the direction of the toroidal magnetic field. The wave excited at the outlet of the wave guide array is a progressive wave propagating in the direction opposite to that of the toroidal current and is, therefore, not absorbed by so-called "runaway" electrons.

  17. Heat flow diagnostics for helicon plasmas

    SciTech Connect

    Berisford, Daniel F.; Bengtson, Roger D.; Raja, Laxminarayan L.; Cassady, Leonard D.; Chancery, William J.

    2008-10-15

    We present experimental studies of power balance in an argon helicon discharge. An infrared camera measures the heating of the dielectric tube containing a helicon discharge based on measurement of temperature profiles of the tube surface before and after a rf pulse. Using this diagnostic, we have measured surface heating trends at a variety of operating conditions on two helicon systems: the 10 kW VASIMR VX-50 experiment and the University of Texas at Austin 1 kW helicon experiment. Power losses downstream from the antenna are measured using thermocouples and probes. The heating of the dielectric tube increases with decreasing magnetic fields, higher gas flow rates, and higher molecular mass of the gas. These preliminary results suggest that cross-field particle diffusion contributes a significant proportion of the energy flux to the wall.

  18. Strong electron heating in the near-Earth plasma sheet.

    NASA Astrophysics Data System (ADS)

    Grigorenko, Elena; Zelenyi, Lev; Kronberg, Elena; Daly, Patrick

    2016-07-01

    Strong perturbations of the Plasma Sheet (PS) magnetic field in the course of magnetic dipolarization are often followed by the generation of magnetic turbulence and plasma heating. Various plasma instabilities and waves can be excited during these processes, which may affect ion and electron velocity distributions in a different way. We have analyzed 70 crossings of the central PS by Cluster spacecraft (s/c) at -19 < X < -8 Re in 2001-2005. We have found that in 32 intervals the ratio of Tion/Tele dropped in the central PS down to <3.0, which denotes significant electron heating. The detailed analysis of these crossings showed that in majority of these events strong magnetic dipolarizations and magnetic turbulence were observed. In the present study we discuss possible mechanisms of such strong electron heating.

  19. Numerical simulation of plasma processes driven by transverse ion heating

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Chan, C. B.

    1993-01-01

    The plasma processes driven by transverse ion heating in a diverging flux tube are investigated with numerical simulation. The heating is found to drive a host of plasma processes, in addition to the well-known phenomenon of ion conics. The downward electric field near the reverse shock generates a doublestreaming situation consisting of two upflowing ion populations with different average flow velocities. The electric field in the reverse shock region is modulated by the ion-ion instability driven by the multistreaming ions. The oscillating fields in this region have the possibility of heating electrons. These results from the simulations are compared with results from a previous study based on a hydrodynamical model. Effects of spatial resolutions provided by simulations on the evolution of the plasma are discussed.

  20. Parallel resistivity and ohmic heating of laboratory dipole plasmas

    SciTech Connect

    Fox, W.

    2012-08-15

    The parallel resistivity is calculated in the long-mean-free-path regime for the dipole plasma geometry; this is shown to be a neoclassical transport problem in the limit of a small number of circulating electrons. In this regime, the resistivity is substantially higher than the Spitzer resistivity due to the magnetic trapping of a majority of the electrons. This suggests that heating the outer flux surfaces of the plasma with low-frequency parallel electric fields can be substantially more efficient than might be naively estimated. Such a skin-current heating scheme is analyzed by deriving an equation for diffusion of skin currents into the plasma, from which quantities such as the resistive skin-depth, lumped-circuit impedance, and power deposited in the plasma can be estimated. Numerical estimates indicate that this may be a simple and efficient way to couple power into experiments in this geometry.

  1. ICRF Heating and Beta Enhancement of HBT-EP Plasmas

    NASA Astrophysics Data System (ADS)

    James, R.; Cates, C.; Klein, A.; Liu, Y.; Mauel, M. E.; Maurer, D. A.; Navratil, G. A.; Pedersen, T. S.; Shilov, M.; Stillits, N.

    2004-11-01

    We describe experiments using the HBT-EP dual strap, inside launch ICRF heating system. RF heating is applied at 4.5MHz to deuterium discharges with 20 percent hydrogen minority species in order to heat electrons in the strongly damped mode-conversion regime. Experiments to date have shown antenna loading with plasmas pre-programmed to be strongly limited on the high field side (HFS) limiter. A HFS triple probe measures electron temperature and density near the antenna, and an RF pickup coil is employed to measure the fluctuating wave magnetic field. Experiments to date indicate that increased plasma density near the antenna improves coupling significantly. We will report on our progress in improving antenna-plasma coupling using the radial position feedback control system (RPFCS) in conjunction with the bias probe to achieve high plasma density near the antenna. Any bias probe induced H-modes may also help increase antenna coupling by increasing the plasma density near the edge. Progress on analysis and diagnosis of the antenna-oscillator circuit and loading measurements and current status of measurable RF heating will be presented.[1] [1] Collaboration with J. Hosea, R. Wilson, R. Budny, S. Paul et al., PPPL

  2. Laser production and heating of plasma for MHD application

    NASA Technical Reports Server (NTRS)

    Jalufka, N. W.

    1988-01-01

    Experiments have been made on the production and heating of plasmas by the absorption of laser radiation. These experiments were performed to ascertain the feasibility of using laser-produced or laser-heated plasmas as the input for a magnetohydrodynamic (MHD) generator. Such a system would have a broad application as a laser-to-electricity energy converter for space power transmission. Experiments with a 100-J-pulsed CO2 laser were conducted to investigate the breakdown of argon gas by a high-intensity laser beam, the parameters (electron density and temperature) of the plasma produced, and the formation and propagation of laser-supported detonation (LSD) waves. Experiments were also carried out using a 1-J-pulsed CO2 laser to heat the plasma produced in a shock tube. The shock-tube hydrogen plasma reached electron densities of approximately 10 to the 17th/cu cm and electron temperatures of approximately 1 eV. Absorption of the CO2 laser beam by the plasma was measured, and up to approximately 100 percent absorption was observed. Measurements with a small MHD generator showed that the energy extraction efficiency could be very large with values up to 56 percent being measured.

  3. Anisotropic radiative transfer problem in optically thick, strongly magnetized plasma: A comparison of results

    SciTech Connect

    Pavlov, G.G.; Shibanov, Y.A.; Silantev, N.A.; Nagel, W.

    1985-04-01

    Recently developed methods for solving the coherent radiative transferproblem in a strongly magnetized plasma are compared and analyzed for the caseof a semi-infinite, homogeneous plasma with the magnetic field perpendicular to the surface. The work of Meszaros and Bonazzola is shown to contain some errors. The accuracy of numerical methods proposed by Silant'ev and Nagel is investigated for various plasma parameters and photon energies. The coupled diffusion approximation developed by Nagel and Kaminker et al. appears to give quite satisfactory results and seems to be more efficient in many cases than direct numerical methods.

  4. An RF heated tandem mirror plasma propulsion study

    SciTech Connect

    Yang, T.F.; Yao, X.; Peng, S.; Krueger, W.A.; Chang-Diaz, F.R.

    1989-01-01

    Experimental results on a tandem mirror hybrid plume rocket involving a three-stage system of plasma injection, heating, and subsequent injection through a magnetic nozzle are presented. In the experiments, a plasma is created by breaking down the gas with electron cyclotron resonance heating at 2 kW in the central cell, and the ion species is then heated to high temperatures with ion cyclotron resonance heating at 10 kW in the end cell. A Langmuir probe measured an electron density of 2.5 x 10 to the 16th/cu m and a temperature of 100 eV in the central cell and an ion density of 1.25 x 10 to the 17th/cu m and a temperature of 500 eV in the end cell. 6 refs.

  5. About MHD heating of plasmaspheric and ionospheric plasmas

    NASA Astrophysics Data System (ADS)

    Pilipenko, V. A.; Buechner, J.; Kirchner, T.

    In recent years, the possibility has been considered to provide supplementary MHD heating to a Tokamak plasma on the basis of an approach involving resonant mode conversion of a magnetosonic wave into a kinetic Alfven wave. The present paper has the objective to study Alfven resonance heating under magnetospheric conditions. The conducted investigation takes into account the damping of an Alfven wave in the ionosphere, a phenomenon, which has not been considered in some previous studies. The employed model is not restricted to the consideration of an approximation of the plasma density by a linear profile, and arbitrary, smooth characteristics are contemplated. The employed model of the magnetosphere corresponds to the model described by Southwood (1974). The rate of energy dissipation at the point of Alfven resonance is calculated, and Joule heating of the ionosphere caused by dissipation of resonant Alfven waves is estimated. MHD waves of sufficient intensity can induce anomalous heating of plasmaspheric particles near the point of resonance.

  6. Angular distribution and polarization of the continuum emission in anisotropic plasmas

    NASA Astrophysics Data System (ADS)

    Lamoureux, M.; Jacquet, L.; Pratt, R. H.

    1989-06-01

    This study illustrates the interest of continuum spectra resolved in angle and polarization for investigating the anisotropy of a plasma. After discussing the validity of two types of relatively simple atomic bremsstrahlung cross sections, we establish easily usable expressions for the continuum emissivity coefficients (emission due to bremsstrahlung and direct radiative recombination) appropriate for electron distributions of a plasma with toroidal symmetry. In the example of a tokamak plasma, the distribution functions for the superthermal electrons were obtained from a Monte Carlo code. The simulated and experimental spectra (measured only in one direction of observation and with no polarization resolution) are in good agreement. The theoretical evaluations show the interest of more detailed measurements. The predicted dependence of the intensity of radiation on the direction of observation and the predicted polarization are large, and they would be a good means to probe the evaluation of the electron distributions in detail and, more generally, to diagnose the anisotropy of the free electrons in plasmas.

  7. Dissipation and turbulent heating of plasma in Jupiter's magnetosphere

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.

    1981-01-01

    Voyager 1 observations of plasma waves in the dayside Jovian magnetosphere which show a correlation with measurements of localized concentrations of cool thermal plasma are presented. This moderately intense broadband electrostatic noise is shown to be of sufficient intensity to accelerate superthermal ions to energies approximately 1 keV and higher. This process can account for the extensive heating of plasma in the magnetosphere and can energize a fraction of heavy ions to injection threshold for a high-energy second stage acceleration mechanism. A brief discussion of the relation of this noise to Jovian magnetospheric dynamics is included.

  8. Ion drag force on a small grain in highly collisional weakly anisotropic plasma: Effect of plasma production and loss mechanisms

    SciTech Connect

    Chaudhuri, M.; Khrapak, S. A.; Morfill, G. E.

    2008-05-15

    The ion drag force acting on a small absorbing grain has been calculated in highly collisional plasma with slowly drifting ions taking into account plasma production and loss processes in the vicinity of the grain. It is shown that the strength of the plasma production and loss mechanisms not only affects the magnitude of the ion drag force, but also determines the direction of the force. The parameter regimes for the ''positive'' and ''negative'' ion drag forces have been identified. In addition, the qualitative features of the electric potential distribution around the grain in isotropic conditions (in the absence of the ion drift) are investigated.

  9. Heating mechanisms and mode changes in helicon plasmas

    NASA Astrophysics Data System (ADS)

    Ellingboe, Albert R.

    1996-10-01

    Measurements of plasma wave fields and time-dependent (within the rf cycle) warm electron density give insight into near-resonant transit time heating of electrons in a helicon plasma source. Experimentally, rf power and magnetic field are found to determine the mode of coupling (E, H, or Wave (A. R. Ellingboe and R. W. Boswell, Physics of Plasmas, July (1996).)) with significant warm electron density only in W mode. A second Wave mode which yields an order of magnitude increase in warm electron current is identified as the second axial eigenmode of the antenna. The turn-on of the second axial eigenmode prior to the second radial eigenmode is predicted by the ANTENA computer code(B. McVey, Plasma Fusion Center, Massachesetts Institute of Technology, Report No. PFC/RR-84-12). Orbit code modeling of the wave-particle interaction finds that increased plasma and/or neutral density significantly degrades interaction because of collisions.

  10. ICRF heating of deuterium-tritium plasmas in TFTR

    SciTech Connect

    Taylor, G.; Murakami, M.; Adler, H.

    1995-03-01

    The first experiments to heat D-T plasmas in the ion cyclotron range of frequencies (ICRF) have been performed on the Tokamak Fusion Test Reactor (TFTR). These experiments have two major objectives: to study the RF physics of ICRF-heated D-T plasmas and to enhance the performance of D-T discharges. Experiments have been conducted at 43 MHz with out-of-phase current strap excitation to explore n{sub T}/n{sub e} concentrations up to approximately 40%. In these experiments n{sub T}/n{sub e} was limited by D recycling from the carbon walls. The location of the T resonance was varied by changing the toroidal magnetic field, and the RF power was modulated (f{sub mod}=5-10 Hz) to elucidate competing heating mechanisms. Up to 5.8 MW of ICRF heating has been coupled into D-T plasmas. The addition of 5.5 MW of ICRF heating to a D-T supershot resulted in an increase in central ion temperature from 26 to 36 keV and an increase in central electron temperature from 8 to 10.5 keV. Up to 80% of the absorbed ICRF power was coupled directly to ions, in good agreement with computer code predictions. These results extrapolate to efficient T heating in future devices such as ITER.

  11. Pre-equilibrium dilepton production from an anisotropic quark-gluon plasma

    SciTech Connect

    Martinez, Mauricio; Strickland, Michael

    2008-09-15

    We calculate leading-order dilepton yields from a quark-gluon plasma that has a time-dependent anisotropy in momentum space. Such anisotropies can arise during the earliest stages of quark-gluon plasma evolution due to the rapid longitudinal expansion of the created matter. Two phenomenological models for the proper-time dependence of the parton hard momentum scale, p{sub hard}, and the plasma anisotropy parameter, {xi}, are constructed that describe the transition of the plasma from its initial nonequilibrium state to an isotropic thermalized state. The first model constructed interpolates between 1+1 dimensional free streaming at early times and 1+1 dimensional ideal hydrodynamical expansion at late times. In the second model we include the effect of collisional broadening of the parton distribution functions in the early-time pre-equilibrium stage of plasma evolution. We find for both cases that for fixed initial conditions high-energy dilepton production is enhanced by pre-equilibrium emission. When the models are constrained to fixed final pion multiplicity the dependence of the resulting spectra on the assumed plasma isotropization time is reduced. Using our most realistic collisionally broadened model we find that high-transverse-momentum dilepton production would be enhanced by at most 40% at the Relativistic Heavy Ion Collider and 50% at the CERN Large Hadron Collider if one assumes an isotropization/thermalization time of 2 fm/c. Given sufficiently precise experimental data this enhancement could be used to determine the plasma isotropization time experimentally.

  12. Plasma heating with multi-MeV neutral impurity beams

    SciTech Connect

    Grisham, L.R.; Post, D.E.; Eubank, H.P.; Firestone, M.; Mikkelsen, D.R.; Singer, C.E.; Weisheit, J.

    1981-03-01

    The utility of neutral beams of A greater than or equal to 6 AMU formed from negative ions, accelerated to approx. 1 MeV/AMU and neutralized, is explored for heating toroidally confined plasmas. Such beams offer the promise of significant advantages relative to conventional neutral beams based upon positive or negative hydrogen ions at 100 to 200 keV/AMU.

  13. Advances in induction-heated plasma torch technology

    NASA Technical Reports Server (NTRS)

    Poole, J. W.; Vogel, C. E.

    1972-01-01

    Continuing research has resulted in significant advances in induction-heated plasma torch technology which extend and enhance its potential for broad range of uses in chemical processing, materials development and testing, and development of large illumination sources. Summaries of these advances are briefly described.

  14. Tridimensional Burning Structures Associated with Anisotropic Thermal Conductivities in Magnetically Confined and Pulsar Plasmas

    NASA Astrophysics Data System (ADS)

    Cardinali, A.; Coppi, B.; Sonnino, G.

    2015-11-01

    A surprising result of the most recent theory of the thermonuclear instability, which can take place in D-T plasmas close to ignition, is that it can develop with tridimensional structures emerging from an axisymmetric toroidal confinement configurations. These structures are helical filaments (``snakes'') that are localized radially around a given rational magnetic surface. Until now well known analyses of fusion burning processes in magnetically confined plasmas, that include the thermonuclear instability, have been carried out by 1+1/2 D transport codes and, consequently, the onset of tri-dimensional structures has not been investigated. The importance of the electron thermal conductivities anisotropy is pointed out also for the inhomogeneous thermonuclear burning of plasmas on the surface of pulsars and for the formation of the observed bright spots on some of them. Sponsored in part by the U.S. DoE.

  15. Intermittent Dissipation and Heating in 3D Kinetic Plasma Turbulence.

    PubMed

    Wan, M; Matthaeus, W H; Roytershteyn, V; Karimabadi, H; Parashar, T; Wu, P; Shay, M

    2015-05-01

    High resolution, fully kinetic, three dimensional (3D) simulation of collisionless plasma turbulence shows the development of turbulence characterized by sheetlike current density structures spanning a range of scales. The nonlinear evolution is initialized with a long wavelength isotropic spectrum of fluctuations having polarizations transverse to an imposed mean magnetic field. We present evidence that these current sheet structures are sites for heating and dissipation, and that stronger currents signify higher dissipation rates. The analyses focus on quantities such as J·E, electron, and proton temperatures, and conditional averages of these quantities based on local electric current density. Evidently, kinetic scale plasma, like magnetohydrodynamics, becomes intermittent due to current sheet formation, leading to the expectation that heating and dissipation in astrophysical and space plasmas may be highly nonuniform. Comparison with previous results from 2D kinetic simulations, as well as high frequency solar wind observational data, are discussed. PMID:25978241

  16. Radio-frequency heating of the coronal plasma during flares

    NASA Technical Reports Server (NTRS)

    Melrose, D. B.; Dulk, G. A.

    1984-01-01

    A model is developed for the radio-frequency (RF) heating of soft X-ray emitting plasma in solar flares due to absorption of amplified cyclotron radiation. The radiation, carrying approximately 10 to the 27th to approximately 10 to the 30th erg/s, is generated through maser emission following partial precipitation of electrons in one or more flaring loops. The maser operates in a large number of small regions, each producing an 'elementary burst' (EB) of short duration. This radiation propagates either directly or after reflection to the second-harmonic absorption layer, where it is absorbed by thermal electrons. The properties of EBs and the heating of the electrons in the absorption layer are discussed in detail. RF heating and evaporation models for the production of soft X-ray emitting plasma are compared. Properties of the RF heating model that explain observed features are energy transport across field lines, rapid heating (in approximately 1 s) of coronal plasma to approximately 3 x 10 to the 7th K, and instigation of turbulent velocities up to the ion sound speed.

  17. Kinetic description of rotating Tokamak plasmas with anisotropic temperatures in the collisionless regime

    SciTech Connect

    Cremaschini, Claudio; Tessarotto, Massimo

    2011-11-15

    A largely unsolved theoretical issue in controlled fusion research is the consistent kinetic treatment of slowly-time varying plasma states occurring in collisionless and magnetized axisymmetric plasmas. The phenomenology may include finite pressure anisotropies as well as strong toroidal and poloidal differential rotation, characteristic of Tokamak plasmas. Despite the fact that physical phenomena occurring in fusion plasmas depend fundamentally on the microscopic particle phase-space dynamics, their consistent kinetic treatment remains still essentially unchallenged to date. The goal of this paper is to address the problem within the framework of Vlasov-Maxwell description. The gyrokinetic treatment of charged particles dynamics is adopted for the construction of asymptotic solutions for the quasi-stationary species kinetic distribution functions. These are expressed in terms of the particle exact and adiabatic invariants. The theory relies on a perturbative approach, which permits to construct asymptotic analytical solutions of the Vlasov-Maxwell system. In this way, both diamagnetic and energy corrections are included consistently into the theory. In particular, by imposing suitable kinetic constraints, the existence of generalized bi-Maxwellian asymptotic kinetic equilibria is pointed out. The theory applies for toroidal rotation velocity of the order of the ion thermal speed. These solutions satisfy identically also the constraints imposed by the Maxwell equations, i.e., quasi-neutrality and Ampere's law. As a result, it is shown that, in the presence of nonuniform fluid and EM fields, these kinetic equilibria can sustain simultaneously toroidal differential rotation, quasi-stationary finite poloidal flows and temperature anisotropy.

  18. Whistler Emission and Absorption Coefficients from AN Anisotropic, Multi-Component Plasma Including Dielectric Response

    NASA Astrophysics Data System (ADS)

    Leid, Terrence Vincent

    The emission of electron cyclotron radiation parallel to the magnetic field direction near the fundamental frequency from a fully ionized, multi-component plasma, is investigated for finite (omega)(,p)/(omega)(,c) within the Klimontovich formalism. Each species may have T(,(PARLL)) different from T(,(PERP)) and may possess a loss cone. We use a bi- maxwellian with an analytic loss cone for each component. In addition, the source function for a multi-component plasma is calculated. We find that for a Maxwellian distribution function the emission coefficient is that of a system of shielded charges. It is shown that only in the case of a tenuous Maxwellian plasma is the source function the Rayleigh-Jeans blackbody intensity. For the case of the Maxwellian we present experimental evidence for finite density emission, (omega)('2)(,p)/(omega)('2) >> (beta). We have constructed a computer code that solves the radiative transfer equation. The resulting power spectra are used as an aid in extracting from experimental data the temperature and density of the various components of the TMX-Upgrade end cell plasma. The code compares both the Ellis-Tsakiris scheme for computing the emission coefficient for a multi-component plasma and the finite density multi -component emission coefficient. The Ellis- Tsakiris scheme estimates the emission coefficient by assuming. that each species radiates independently of each other.('1) Results are presented for the case of the TMX -Upgrade tandem mirror device. ('1)R. F. Ellis and G. D. Tsakiris, Nucl. Fusion 23, 1115 (1984).

  19. In-depth plasma-wave heating of dense plasma irradiated by short laser pulses.

    PubMed

    Sherlock, M; Hill, E G; Evans, R G; Rose, S J; Rozmus, W

    2014-12-19

    We investigate the mechanism by which relativistic electron bunches created at the surface of a target irradiated by a very short and intense laser pulse transfer energy to the deeper parts of the target. In existing theories, the dominant heating mechanism is that of resistive heating by the neutralizing return current. In addition to this, we find that large amplitude plasma waves are induced in the plasma in the wake of relativistic electron bunches. The subsequent collisional damping of these waves represents a source of heating that can exceed the resistive heating rate. As a result, solid targets heat significantly faster than has been previously considered. A new hybrid model, capable of reproducing these results, is described. PMID:25554889

  20. Raman amplification in plasma: Wavebreaking and heating effects

    SciTech Connect

    Farmer, J. P.; Ersfeld, B.; Jaroszynski, D. A.

    2010-11-15

    A three-wave model has been developed to investigate the influence of wavebreaking and thermal effects on the Raman amplification in plasma. This has been benchmarked against a particle-in-cell code with positive results. A new regime, the 'thermal chirp' regime, has been identified and illustrated. Here the shift in plasma resonance due to heating of the plasma by a monochromatic pump allows a probe pulse to be amplified and compressed without significant pump depletion. In regimes where damping dominates, it is found that inverse bremsstrahlung dominates at high densities, and improved growth rates may be achieved by preheating the plasma. At low densities or high pump intensities, wavebreaking acts to limit amplification. The inclusion of thermal effects can dramatically reduce the peak attainable intensity because of the reduced wavebreaking limit at finite temperatures.

  1. Plasma heating and emission of runaway charged particles in a plasma focus device

    NASA Astrophysics Data System (ADS)

    Behbahani, R. A.; Hirose, A.; Xiao, C.

    2016-03-01

    The required experimental E-field across plasma to generate significant runaway electrons and hard X-rays during the pinch phase and the phase with anomalous resistance has been investigated in a dense plasma focus. The plasma voltage and inductance have been measured in a plasma focus with two different anode tip structures. The results show a significant generation of charged particles and hard X-rays at smaller E-field across the plasma column in the phase of anomalous resistances compared to the pinch phase. Plasma heating process may enhance the rate of runaway-charged-particle generation due to the combined effects of a reduced Dreicer field and the avalanche effects during the phase of anomalous resistance.

  2. ION HEATING IN INHOMOGENEOUS EXPANDING SOLAR WIND PLASMA: THE ROLE OF PARALLEL AND OBLIQUE ION-CYCLOTRON WAVES

    SciTech Connect

    Ozak, N.; Ofman, L.; Viñas, A.-F.

    2015-01-20

    Remote sensing observations of coronal holes show that heavy ions are hotter than protons and their temperature is anisotropic. In-situ observations of fast solar wind streams provide direct evidence for turbulent Alfvén wave spectrum, left-hand polarized ion-cyclotron waves, and He{sup ++} - proton drift in the solar wind plasma, which can produce temperature anisotropies by resonant absorption and perpendicular heating of the ions. Furthermore, the solar wind is expected to be inhomogeneous on decreasing scales approaching the Sun. We study the heating of solar wind ions in inhomogeneous plasma with a 2.5D hybrid code. We include the expansion of the solar wind in an inhomogeneous plasma background, combined with the effects of a turbulent wave spectrum of Alfvénic fluctuations and initial ion-proton drifts. We study the influence of these effects on the perpendicular ion heating and cooling and on the spectrum of the magnetic fluctuations in the inhomogeneous background wind. We find that inhomogeneities in the plasma lead to enhanced heating compared to the homogenous solar wind, and the generation of significant power of oblique waves in the solar wind plasma. The cooling effect due to the expansion is not significant for super-Alfvénic drifts, and is diminished further when we include an inhomogeneous background density. We reproduce the ion temperature anisotropy seen in observations and previous models, which is present regardless of the perpendicular cooling due to solar wind expansion. We conclude that small scale inhomogeneities in the inner heliosphere can significantly affect resonant wave ion heating.

  3. Asymptotic-preserving Lagrangian approach for modeling anisotropic transport in magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Chacon, Luis; Del-Castillo-Negrete, Diego

    2012-03-01

    Modeling electron transport in magnetized plasmas is extremely challenging due to the extreme anisotropy between parallel (to the magnetic field) and perpendicular directions (the transport-coefficient ratio χ/χ˜10^10 in fusion plasmas). Recently, a novel Lagrangian Green's function method has been proposedfootnotetextD. del-Castillo-Negrete, L. Chac'on, PRL, 106, 195004 (2011); D. del-Castillo-Negrete, L. Chac'on, Phys. Plasmas, submitted (2011) to solve the local and non-local purely parallel transport equation in general 3D magnetic fields. The approach avoids numerical pollution, is inherently positivity-preserving, and is scalable algorithmically (i.e., work per degree-of-freedom is grid-independent). In this poster, we discuss the extension of the Lagrangian Green's function approach to include perpendicular transport terms and sources. We present an asymptotic-preserving numerical formulation, which ensures a consistent numerical discretization temporally and spatially for arbitrary χ/χ ratios. We will demonstrate the potential of the approach with various challenging configurations, including the case of transport across a magnetic island in cylindrical geometry.

  4. Rotochemical heating of millisecond and classical pulsars with anisotropic and density-dependent superfluid gap models

    NASA Astrophysics Data System (ADS)

    González-Jiménez, Nicolás; Petrovich, Cristobal; Reisenegger, Andreas

    2015-03-01

    When a rotating neutron star loses angular momentum, the progressive reduction of the centrifugal force makes it contract. This perturbs each fluid element, raising the local pressure and originating deviations from beta equilibrium, inducing reactions that release heat (`rotochemical heating'). This effect has previously been studied by Fernández & Reisenegger for non-superfluid neutron stars and by Petrovich & Reisenegger for superfluid millisecond pulsars. Both studies found that pulsars reach a quasi-steady state in which the compression driving the matter out of beta equilibrium is balanced by the reactions trying to restore the equilibrium. We extend previous studies by considering the effect of density-dependence and anisotropy of the superfluid energy gaps, for the case in which the dominant reactions are the modified Urca processes, the protons are non-superconducting, and the neutron superfluidity is parametrized by models proposed in the literature. By comparing our predictions with the surface temperature of the millisecond pulsar PSR J0437-4715 and upper limits for 21 classical pulsars, we find the millisecond pulsar can be only explained by the models with the effectively largest energy gaps (type B models), the classical pulsars require with the gap models that vanish for some angle (type C) and two different envelope compositions. Thus, no single model for neutron superfluidity can simultaneously account for the thermal emission of all available observations of non-accreting neutron stars, possibly due to our neglect of proton superconductivity.

  5. Characterization of the Inductively Heated Plasma Source IPG6-B

    NASA Astrophysics Data System (ADS)

    Dropmann, Michael; Laufer, Rene; Herdrich, Georg; Matthews, Lorin; Hyde, Truell

    2014-10-01

    In close collaboration between the Center for Astrophysics, Space Physics and Engineering Research (CASPER) at Baylor University, Texas, and the Institute of Space Systems (IRS) at the University of Stuttgart, Germany, two plasma facilities have been established using the Inductively heated Plasma Generator 6 (IPG6). The facility at Baylor University (IPG6-B) works at a frequency of 13.56 MHz and a maximum power of 15 kW. A vacuum pump of 160 m3/h in combination with a butterfly valve allows pressure control over a wide range. Intended fields of research include basic investigation into thermo-chemistry and plasma radiation, space plasma environments and high heat fluxes e.g. those found in fusion devices or during atmospheric re-entry of spacecraft. After moving the IPG6-B facility to the Baylor Research and Innovation Collaborative (BRIC) it was placed back into operation during the summer of 2014. Initial characterization in the new lab, using a heat flux probe, Pitot probe and cavity calorimeter, has been conducted for Air, Argon and Helium. The results of this characterization are presented.

  6. Particle Acceleration and Plasma Heating in the Chromosphere

    NASA Astrophysics Data System (ADS)

    Zaitsev, V. V.; Stepanov, A. V.

    2015-12-01

    We propose a new mechanism of electron acceleration and plasma heating in the solar chromosphere, based on the magnetic Rayleigh-Taylor instability. The instability develops at the chromospheric footpoints of a flare loop and deforms the local magnetic field. As a result, the electric current in the loop varies, and a resulting inductive electric field appears. A pulse of the induced electric field, together with the pulse of the electric current, propagates along the loop with the Alfvén velocity and begins to accelerate electrons up to an energy of about 1 MeV. Accelerated particles are thermalized in the dense layers of the chromosphere with the plasma density n ≈10^{14} - 10^{15} cm^{-3}, heating them to a temperature of about several million degrees. Joule dissipation of the electric current pulse heats the chromosphere at heights that correspond to densities n ≤10^{11} - 10^{13} cm^{-3}. Observations with the New Solar Telescope at Big Bear Solar Observatory indicate that chromospheric footpoints of coronal loops might be heated to coronal temperatures and that hot plasma might be injected upwards, which brightens ultra-fine loops from the photosphere to the base of the corona. Thereby, recent observations of the Sun and the model we propose stimulate a déjà vu - they are reminiscent of the concept of the chromospheric flare.

  7. Anomalous resistivity and heating in current-driven plasma thrusters

    NASA Astrophysics Data System (ADS)

    Choueiri, E. Y.

    1999-05-01

    A theory is presented of anomalous resistivity and particle heating in current-driven plasma accelerators such as the magnetoplasmadynamic thruster (MPDT). An electromagnetic dielectric tensor is used for a current-carrying, collisional and finite-beta plasma and it is found that an instability akin to the generalized lower hybrid drift instability (GLHDI) exists for electromagnetic modes (i.e., with finite polarization). Weak turbulence theory is then used to develop a second-order description of the heating rates of particles by the waves and the electron-wave momentum exchange rate that controls the anomalous resistivity effect. It is found that the electron Hall parameter strongly scales the level of anomalous dissipation for the case of the MPDT plasma. This scaling has recently been confirmed experimentally [Phys. Plasmas 5, 3581 (1997)]. Polynomial expressions of the relevant transport coefficients cast solely in terms of macroscopic parameters are also obtained for including microturbulence effects in numerical plasma fluid models used for thruster flow simulation.

  8. Sawtooth stability in neutral beam heated plasmas in TEXTOR

    NASA Astrophysics Data System (ADS)

    Chapman, I. T.; Pinches, S. D.; Koslowski, H. R.; Liang, Y.; Krämer-Flecken, A.; TEXTOR Team; de Bock, M.

    2008-03-01

    The experimental sawtooth behaviour in neutral beam injection (NBI) heated plasmas in TEXTOR is described. It is found that the sawtooth period is minimized with a low NBI power oriented in the same direction as the plasma current. As the beam power is increased in the opposite direction to the plasma current, the sawtooth period increases to a maximum before it begins to shorten once more. Results from both magnetohydrodynamic stability modelling including toroidal flows and modelling of the kinetic effects of the fast ions resulting from NBI heating are also presented. This model combining the gyroscopic and kinetic effects upon the stability of the n = 1 internal kink mode—thought to be associated with sawtooth oscillations—qualitatively recovers the sawtooth behaviour exhibited in the experiment. It is proposed that the sawtooth period is minimized in the co-NBI direction at the point at which the stabilization of the kink mode due to rotation is weakest. This occurs when the plasma rotation induced by the NBI balances the intrinsic rotation of the plasma. The sawtooth behaviour in the counter-NBI regime is attributed to a subtle balance of the competing stabilization from the toroidal rotation and destabilization from the presence of energetic ions.

  9. Polarized Heα Radiation by Anisotropic Fast Electron Transport in Ultra-Intense Laser Produced Plasmas

    NASA Astrophysics Data System (ADS)

    Kawamura, T.; Kai, T.; Koike, F.; Nakazaki, S.; Nishimura, H.; Inubushi, Y.; Okano, Y.; Nagatomo, H.; Batani, D.; Morace, A.; Redaelli, R.; Fourment, C.; Santos, J.; Malka, G.; Boscheron, A.; Casner, A.; Koenig, M.; Fujioka, S.; Nakamura, T.; Johzaki, T.; Mima, K.

    2009-09-01

    In fast ignition research, the transport dynamics of fast electrons is one of the critical issues. Fast electrons generated by an intense laser pulse show a highly anisotropic velocity distribution. To gain insight into the anisotropy of the velocity distribution of fast electrons, polarized x-ray spectroscopy has been proposed. The polarization spectroscopy of Cl Heα radiation was experimentally demonstrated at 1017 W/cm2 (˜100 mJ in 130 fs), and a new time-dependent atomic population kinetics code was also developed. It predicts that the high polarization arises only in a low-density region of the target plasma. Additional x-ray polarization measurements were done at 101717-18 W/cm2 (˜10 J in ˜1 ps). Polarization was measured as a function of the overcoat thickness of a target. The polarization is negative in the shallow region near the target surface, and becomes near zero at the laser intensity of ˜1018 W/cm2. At ˜1017 W/cm2, the polarization varies from negative to positive, and finally zero along with an increase in the overcoat thickness.

  10. Cold plasma heating in the plasma sheet boundary layer - Theory and simulations

    NASA Technical Reports Server (NTRS)

    Schriver, David; Ashour-Abdalla, Maha

    1990-01-01

    Satellite observations in recent years have confirmed that the plasma sheet boundary layer is a permanent feature of the earth's magnetotail located between the lobe and central plasma sheet during both quiet and active magnetic periods. Distinct features of the boundary layer include field aligned ion beams and intense electrostatic emissions known as broadband electrostatic noise. Since the plasma sheet boundary layer is a spatial feature of the magnetotail, within it will occur thermal mixing of the resident warm boundary layer plasma with inflowing (convecting) cold ionospheric plasma. A theoretical study involving linear theory and nonlinear numerical particle simulations is presented which examines ion beam instabilities in the presence of a thermally mixed hot and cold background plasma. It is found that the free energy in the ion beams can heat the cool ionospheric plasma to ambient plasma sheet boundary layer temperatures via broadband electrostatic noise. These results, along with recent observational reports that ionospheric outflow can account for measured plasma sheet densities, suggest that the ionospheric role in plasma sheet dynamics and content may be as large as the solar wind.

  11. Heat flow in variable polarity plasma arc welds

    NASA Technical Reports Server (NTRS)

    Abdelmessih, Amanie N.

    1992-01-01

    The space shuttle external tank and the space station Freedom are fabricated by the variable polarity plasma arc (VPPA) welding. Heat sink effects (taper) are observed when there are irregularities in the work-piece configuration especially if these irregularities are close to the weld bead. These heat sinks affect the geometry of the weld bead, and in extreme cases they could cause defects such as incomplete fusion. Also, different fixtures seem to have varying heat sink effects. The objective of the previous, present, and consecutive research studies is to investigate the effect of irregularities in the work-piece configuration and fixture differences on the weld bead geometry with the ultimate objective to compensate automatically for the heat sink effects and achieve a perfect weld.

  12. Interaction of adhered metallic dust with transient plasma heat loads

    NASA Astrophysics Data System (ADS)

    Ratynskaia, S.; Tolias, P.; Bykov, I.; Rudakov, D.; De Angeli, M.; Vignitchouk, L.; Ripamonti, D.; Riva, G.; Bardin, S.; van der Meiden, H.; Vernimmen, J.; Bystrov, K.; De Temmerman, G.

    2016-06-01

    The first study of the interaction of metallic dust (tungsten, aluminum) adhered on tungsten substrates with transient plasma heat loads is presented. Experiments were carried out in the Pilot-PSI linear device with transient heat fluxes up to 550 MW m‑2 and in the DIII-D divertor tokamak. The central role of the dust-substrate contact area in heat conduction is highlighted and confirmed by heat transfer simulations. The experiments provide evidence of the occurrence of wetting-induced coagulation, a novel growth mechanism where cluster melting accompanied by droplet wetting leads to the formation of larger grains. The physical processes behind this mechanism are elucidated. The remobilization activity of the newly formed dust and the survivability of tungsten dust on hot surfaces are documented and discussed in the light of implications for ITER.

  13. Heat flow in variable polarity plasma arc welds

    NASA Astrophysics Data System (ADS)

    Abdelmessih, Amanie N.

    1992-12-01

    The space shuttle external tank and the space station Freedom are fabricated by the variable polarity plasma arc (VPPA) welding. Heat sink effects (taper) are observed when there are irregularities in the work-piece configuration especially if these irregularities are close to the weld bead. These heat sinks affect the geometry of the weld bead, and in extreme cases they could cause defects such as incomplete fusion. Also, different fixtures seem to have varying heat sink effects. The objective of the previous, present, and consecutive research studies is to investigate the effect of irregularities in the work-piece configuration and fixture differences on the weld bead geometry with the ultimate objective to compensate automatically for the heat sink effects and achieve a perfect weld.

  14. Plasma Heating and Ultrafast Semiconductor Laser Modulation Through a Terahertz Heating Field

    NASA Technical Reports Server (NTRS)

    Li, Jian-Zhong; Ning, C. Z.

    2000-01-01

    Electron-hole plasma heating and ultrafast modulation in a semiconductor laser under a terahertz electrical field are investigated using a set of hydrodynamic equations derived from the semiconductor Bloch equations. The self-consistent treatment of lasing and heating processes leads to the prediction of a strong saturation and degradation of modulation depth even at moderate terahertz field intensity. This saturation places a severe limit to bandwidth achievable with such scheme in ultrafast modulation. Strategies for increasing modulation depth are discussed.

  15. Magnetic-divertor stabilization of an axisymmetric plasma with anisotropic temperature

    SciTech Connect

    Sasagawa, Y.; Katanuma, I.; Mizoguchi, Y.; Cho, T.; Pastukhov, V. P.

    2006-12-15

    Magnetohydrodynamic stabilization of an axisymmetric mirror plasma with a magnetic divertor is studied. An equation is found for the flute modes, which includes the stabilizing influence of ion temperature anisotropy and nonparaxial magnetic fields, as well as a finite ion Larmor radius. It is shown that if the density profile is sufficiently gentle, then the nonparaxial configuration can stabilize all modes as long as ion temperature is radially uniform. This can be demonstrated even when the density vanishes on the separatrix and even for small ion Larmor radii. It is found, however, that the ion temperature gradient makes the unstable region wider; high ion temperature is required to stabilize the flute mode.

  16. Reflection of electromagnetic radiation from plasma with an anisotropic electron velocity distribution

    SciTech Connect

    Vagin, K. Yu. Uryupin, S. A.

    2013-08-15

    The reflection of a test electromagnetic pulse from the plasma formed as a result of tunnel ionization of atoms in the field of a circularly polarized high-power radiation pulse is analyzed using the kinetic approach to describe electron motion. It is shown that the reflected pulse is significantly amplified due to the development of Weibel instability. The amplification efficiency is determined by the maximum value of the instability growth rate, which depends on the degree of anisotropy of the photoelectron distribution function.

  17. Obliquely propagating electrostatic waves in a magnetized plasma for different types of anisotropic kappa distribution

    NASA Astrophysics Data System (ADS)

    Bashir, M. F.; Yoon, P. H.; Murtaza, G.; Aqeel, D.; Javed, S.; Zahra, M.

    2015-12-01

    By using the kinetic theory, the dispersion relation of obliquely propagating electrostatic waves are discussed for three types of kappa distribution function: 1) loss-cone-bi-kappa-Maxwellian distribution, 2) current carrying Bi-kappa-Maxwellian distribution and 3) product-bi-kappa distribution. The effects of kappa-index, loss-cone index, streaming velocity and the temperature anisotropy on the Harris instability is highlighted for their possible application to explain the banded emissions observed in the terrestrial magnetosphere and in the magnetospheres of other planets, e.g., Jupiter, Saturn, Uranus, and in Io's plasma torus.

  18. Structure of intermediate shocks in collisionless anisotropic Hall-magnetohydrodynamics plasma models

    SciTech Connect

    Sánchez-Arriaga, G.

    2013-10-15

    The existence of discontinuities within the double-adiabatic Hall-magnetohydrodynamics (MHD) model is discussed. These solutions are transitional layers where some of the plasma properties change from one equilibrium state to another. Under the assumption of traveling wave solutions with velocity C and propagation angle θ with respect to the ambient magnetic field, the Hall-MHD model reduces to a dynamical system and the waves are heteroclinic orbits joining two different fixed points. The analysis of the fixed points rules out the existence of rotational discontinuities. Simple considerations about the Hamiltonian nature of the system show that, unlike dissipative models, the intermediate shock waves are organized in branches in parameter space, i.e., they occur if a given relationship between θ and C is satisfied. Electron-polarized (ion-polarized) shock waves exhibit, in addition to a reversal of the magnetic field component tangential to the shock front, a maximum (minimum) of the magnetic field amplitude. The jumps of the magnetic field and the relative specific volume between the downstream and the upstream states as a function of the plasma properties are presented. The organization in parameter space of localized structures including in the model the influence of finite Larmor radius is discussed.

  19. The polarization electric field and its effects in an anisotropic rotating magnetospheric plasma

    NASA Technical Reports Server (NTRS)

    Huang, T. S.; Birmingham, T. J.

    1992-01-01

    Spatial variations of density and temperature along a magnetic field line are evaluated for a plasma undergoing adiabatic motion in a rotating magnetosphere. The effects of centrifugal and gravitational forces are accounted for, as is anisotropy in the pitch angle distribution functions of individual species. A polarization electric field is invoked to eliminate the net electric charge density resulting from the aforementioned mass dependent forces and different anisotropies. The position of maximum density in a two-component, electron-ion plasma is determined both in the absence and in the presence of the polarization effect and compared. A scale height, generalized to include anisotropies, is derived for the density fall-off. The polarization electric field is also included in the parallel guiding center equation; equilibrium points are determined and compared in both individual and average senses with the position of density maximum. Finally a transverse (to magnetic field lines) electric component is deduced as a consequence of dissimilar charge neutralization on adjacent field lines. The E x B velocity resultant from such a 'fringing' electric field is calculated and compared with the magnitude of other drifts.

  20. Numerical simulations of anisotropic plasmas using a modified ZEUS-MP

    NASA Astrophysics Data System (ADS)

    Chandran, Benjamin; Tangri, Varun; Sarkar, Aveek; Perez, Jean; Sharma, Prateek

    2012-10-01

    Three dimensional linear and nonlinear simulations of collisionless one-fluid plasmas with pressure anisotropy are presented using the Chew- Goldberger-Low (CGL-MHD) and double-isothermal models. For this purpose, the code ZEUS-MP [J. C. Hayes et. al. The APJ Supplement Series 165 (2006) 188.] has been modified. Major modifications include a changed method of characteristics, new compressive and non-compressive forces, and a ``hard wall'' limit on pressure anisotropy that is intended to mimic the effects of plasma micro-instabilities that limit the temperature anisotropy. For purposes of validation, more than 100 test simulations of linear waves (Alfven, slow and fast), instabilities (firehose and mirror) and nonlinear vortices (Orszag-Tang) are presented for a number of initial conditions and parameters. Finally, this model is used to investigate the way that Alfven-wave turbulence leads to a spreading of the temperature-anisotropy probability distribution in the solar wind. Analysis is completed with a detailed analysis of the fluctuation data.

  1. Wave-Particle Decorrelation and Transport of Anisotropic Turbulence in Collisionless Plasmas

    SciTech Connect

    Lin, Z.; Holod, I.; Chen, L.; Diamond, P. H.; Hahm, T. S.; Ethier, S.

    2007-12-31

    Comprehensive analysis of the largest first-principles simulations to date shows that stochastic wave-particle decorrelation is the dominant mechanism responsible for electron heat transport driven by electron temperature gradient turbulence with extended radial streamers. The transport is proportional to the local fluctuation intensity, and phase-space island overlap leads to a diffusive process with a time scale comparable to the wave-particle decorrelation time, determined by the fluctuation spectral width. This kinetic time scale is much shorter than the fluid time scale of eddy mixing.

  2. Fast collisionless reconnection and electron heating in strongly magnetized plasmas.

    PubMed

    Loureiro, N F; Schekochihin, A A; Zocco, A

    2013-07-12

    Magnetic reconnection in strongly magnetized (low-beta), weakly collisional plasmas is investigated by using a novel fluid-kinetic model [Zocco and Schekochihin, Phys. Plasmas 18, 102309 (2011)] which retains nonisothermal electron kinetics. It is shown that electron heating via Landau damping (linear phase mixing) is the dominant dissipation mechanism. In time, electron heating occurs after the peak of the reconnection rate; in space, it is concentrated along the separatrices of the magnetic island. For sufficiently large systems, the peak reconnection rate is cE(∥)(max) ≈ 0.2v(A)B(y,0), where v(A) is the Alfvén speed based on the reconnecting field B(y,0). The island saturation width is the same as in magnetohydrodynamics models except for small systems, when it becomes comparable to the kinetic scales. PMID:23889411

  3. Generalized dispersion relation for electron Bernstein waves in a non-Maxwellian magnetized anisotropic plasma

    SciTech Connect

    Deeba, F.; Ahmad, Zahoor; Murtaza, G.

    2010-10-15

    A generalized dielectric constant for the electron Bernstein waves using non-Maxwellian distribution functions is derived in a collisionless, uniform magnetized plasma. Using the Neumann series expansion for the products of Bessel functions, we can derive the dispersion relations for both kappa and the generalized (r,q) distributions in a straightforward manner. The dispersion relations now become dependent upon the spectral indices {kappa} and (r,q) for the kappa and the generalized (r,q) distribution, respectively. Our results show how the non-Maxwellian dispersion curves deviate from the Maxwellian depending upon the values of the spectral indices chosen. It may be noted that the (r,q) dispersion relation is reduced to the kappa distribution for r=0 and q={kappa}+1, which, in turn, is further reducible to the Maxwellian distribution for {kappa}{yields}{infinity}.

  4. Anisotropic Ta{sub 2}O{sub 5} waveguide etching using inductively coupled plasma etching

    SciTech Connect

    Muttalib, Muhammad Firdaus A. Chen, Ruiqi Y.; Pearce, Stuart J.; Charlton, Martin D. B.

    2014-07-01

    Smooth and vertical sidewall profiles are required to create low loss rib and ridge waveguides for integrated optical device and solid state laser applications. In this work, inductively coupled plasma (ICP) etching processes are developed to produce high quality low loss tantalum pentoxide (Ta{sub 2}O{sub 5}) waveguides. A mixture of C{sub 4}F{sub 8} and O{sub 2} gas are used in combination with chromium (Cr) hard mask for this purpose. In this paper, the authors make a detailed investigation of the etch process parameter window. Effects of process parameters such as ICP power, platen power, gas flow, and chamber pressure on etch rate and sidewall slope angle are investigated. Chamber pressure is found to be a particularly important factor, which can be used to tune the sidewall slope angle and so prevent undercut.

  5. Generation and Sustainment of Plasma Rotation by ICRF Heating

    NASA Astrophysics Data System (ADS)

    Perkins, F. W.

    2000-10-01

    When tokamak plasmas are heated by the fundamental minority ion-cyclotron process, they are observed to rotate toroidally, even though this heating process introduces negligable angular momentum. This work proposes and evaluates a physics mechanism which resolves this apparent conflict. The argument has two elements. First, it is assumed that angular momentum transport is governed by a diffusion equation with a v_tor = 0 boundary condition at the plasma surface and a torque-density source. When the source consists of separated regions of positive and negative torque density, a finite central rotation velocity results, even though the volume integrated torque density - the angular momentum input - vanishes. Secondly, ions energized by the ICRF process can generate separated regions of positive and negative torque density. Heating increases their banana widths which leads to radial energetic-particle transport that must be balanced by neutralizing radial currents and a j_rB_pR torque density in the bulk plasma. Additional, comparable torque density results from collisional transfer of mechanical angular momentum from energetic particles to the bulk plasma and particle loss through banana particles impacting the wall. Monte-Carlo calculations utilizing the ORBIT code evaluate all sources of torque density and rigorously assure that no net angular momentum is introduced. Two models of ICRF heating, diffusive and instantaneous, give similar results. When the resonance location is on the LFS, the calculated rotation has the magnitude, profile, and co-current sense of Alcator C-Mod observations. For HFS resonance locations, the model predicts counter-current rotation. Scans of rotational profiles vs. resonance location, initial energy, particle loss, pitch, and qm will be presented as will the location of the velocity shear layer its scaling to a reactor.

  6. Compound sawtooth study in ohmically heated TFTR plasmas

    SciTech Connect

    Yamada, H.; McGuire, K.; Colchin, D.; Efthimion, P.C.; Fredrickson, E.; Hill, K.; Kiraly, J.; Pare, V.; Taylor, G.; Sauthoff, N.

    1985-09-01

    Compound sawtooth activity has been observed in ohmically heated, high current, high density TFTR plasmas. Commonly called ''double sawteeth,'' such sequences consist of a repetitive series of subordinate relaxations followed by a main relaxation with a different inversion radius. The period of such compound sawteeth can be as long as 100 msec. In other cases, however, no compound sawteeth or bursts of them can be observed in discharges with essentially the same parameters.

  7. Heat transfer in a fissioning uranium plasma reactor cavity

    NASA Technical Reports Server (NTRS)

    Kascak, A. F.

    1973-01-01

    Two schemes are investigated by which a fission-heated uranium plasma located in the central cavity of a test reactor could be insulated to keep its temperature above condensation in a neutron flux of 10 to the 15th power neutrons/(sq cm)(sec) or less. The first scheme was to use a mirrored cavity wall to reflect the thermal radiation back into the plasma. The second scheme was to seed the transpirational cavity wall coolant so as to make it opaque to thermal radiation, thus insulating the hot plasma from the cold wall. The analysis showed that a mirrored cavity wall must have a reflectivity of over 95 percent or that seeded argon must be used as the wall coolant to give an acceptable operating margin above fuel condensation conditions.

  8. Nonlinear heating of underdense collisional plasma by a laser pulse

    SciTech Connect

    Abari, M. Etehadi; Shokri, B.

    2011-05-15

    The nonlinear interaction of a laser pulse with a homogenous unmagnetized underdense plasma, taking ohmic heating and the effects of ponderomotive force into account, is theoretically studied. Since the ponderomotive force modifies the electrons density and temperature distribution, the nonlinear dielectric permittivity of plasma is obtained in non-relativistic regime. Furthermore, electric and magnetic fields, electron density, temperature distribution, and the effective permittivity variations are obtained in terms of plasma length by making use the steady state solutions of the Maxwell and hydrodynamic equations. It is shown that the oscillations wave length of electric and magnetic fields decreases when the laser intensity increases. At the same time, in this case, electron density oscillations become highly peaked. Also, the amplitude of the electron temperature oscillations increase and their wavelength decreases.

  9. Influence of Multiple Ionization on Studies of Nanoflare Heated Plasmas

    NASA Astrophysics Data System (ADS)

    Hahn, Michael; Savin, Daniel Wolf

    2015-04-01

    The spectrum emitted by a plasma depends on the charge state distribution (CSD) of the gas. This, in turn, is determined by the corresponding rates for electron-impact ionization and recombination. Current CSD calculations for solar physics do not account for electron-impact multiple ionization (EIMI), a process in which multiple electrons are ejected by a single electron-ion collision. We have estimated the EIMI cross sections for all charge states of iron using a combination of the available experimental data and semi-empirical formulae. We then modeled the CSD and observed the influence of EIMI compared to only including single ionization. One case of interest for solar physics is nanoflare heating. Recent work has attempted to predict the spectra of impulsively heated plasmas in order to identify diagnostics arising from non-equilibrium ionization that can constrain the nanoflare properties, but these calculations have ignored EIMI. Our findings suggest that EIMI can have a significant effect on the CSD of a nanoflare-heated plasma, changing the ion abundances by up to about 50%.

  10. Analysis of a microwave-heated planar propagating hydrogen plasma

    SciTech Connect

    Knecht, J.P.; Micci, M.M.

    1988-02-01

    The heating of a gas to high temperatures by absorption of microwave radiation has been proposed as a potential electrothermal rocket propulsion system. One possible mode of microwave energy absorption is by means of a planar plasma region propagating toward the source of the microwave radiation. Such a planar propagating plasma can be spatially stabilized by a gas stream flowing in the same direction as the microwave radiation with a velocity equal to the plasma propagation velocity. A one-dimensional analysis of the microwave-heated planar propagating plasma for hydrogen gas was developed to predict maximum gas temperatures and propagation velocities. The governing electromagnetic and energy equations were numerically integrated with temperature-dependent thermodynamic properties of equilibrium hydrogen. The propagation velocity eigenvalue was solved by means of an iterative technique. Temperature distribution in the gas, propagation velocities, and percent power absorbed, reflected and transmitted, were obtained as a function of incident microwave power at a frequency of 2.45 GHza for hydrogen gas pressures of 1 and 10 atm. 19 references.

  11. MHD discontinuities in solar flares: Continuous transitions and plasma heating

    NASA Astrophysics Data System (ADS)

    Ledentsov, L. S.; Somov, B. V.

    2015-12-01

    The boundary conditions for the ideal MHD equations on a plane discontinuity surface are investigated. It is shown that, for a given mass flux through a discontinuity, its type depends only on the relation between inclination angles of a magnetic field. Moreover, the conservation laws on a surface of discontinuity allow changing a discontinuity type with gradual (continuous) changes in the conditions of plasma flow. Then there are the so-called transition solutions that satisfy simultaneously two types of discontinuities. We obtain all transition solutions on the basis of the complete system of boundary conditions for the MHD equations. We also found the expression describing a jump of internal energy of the plasma flowing through the discontinuity. Firstly, this allows constructing a generalized scheme of possible continuous transitions between MHD discontinuities. Secondly, it enables the examination of the dependence of plasma heating by plasma density and configuration of the magnetic field near the discontinuity surface, i.e., by the type of the MHD discontinuity. It is shown that the best conditions for heating are carried out in the vicinity of a reconnecting current layer near the areas of reverse currents. The result can be helpful in explaining the temperature distributions inside the active regions in the solar corona during flares observed by modern space observatories in soft and hard X-rays.

  12. Voyager observations of lower hybrid noise in the Io plasma torus and anomalous plasma heating rates

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.; Coroniti, F. V.; Kurth, W. S.; Scarf, F. L.

    1985-01-01

    A study of Voyager 1 electric field measurements obtained by the plasma wave instrument in the Io plasma torus has been carried out. A survey of the data has revealed the presence of persistent peaks in electric field spectra in the frequency range 100-600 Hz consistent with their identification as lower hybrid noise for a heavy-ion plasma of sulfur and oxygen. Typical wave intensities are 0.1 mV/m, and the spectra also show significant Doppler broadening, Delta omega/omega approximately 1. A theoretical analysis of lower hybrid wave generation by a bump-on-tail ring distribution of ions is given. The model is appropriate for plasmas with a superthermal pickup ion population present. A general methodology is used to demonstrate that the maximum plasma heating rate possible through anomalous wave-particle heat exchange is less than approximately 10 to the -14th ergs per cu cm per s. Although insufficient to meet the power requirement of the EUV-emitting warm torus, the heating rate is large enough to maintain a low-density (0.01-0.1 percent) superthermal electron population of keV electrons, which may lead to a small but significant anomalous ionization effect.

  13. Jet-conversion photons from an anisotropic quark-gluon plasma

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Lusaka; Roy, Pradip

    2010-10-01

    We calculate the pT distributions of jet-conversion photons from a quark-gluon plasma with pre-equilibrium momentum-space anisotropy. A phenomenological model has been used for the time evolution of the hard momentum scale phard(τ) and anisotropy parameter ξ(τ). As a result of pre-equilibrium momentum-space anisotropy, we find significant modification of the jet-conversion photon pT distribution. For example, with fixed initial condition pre-equilibrium anisotropy, we predict a significant enhancement of the jet-photon pT distribution in the entire region, whereas for pre-equilibrium anisotropy with fixed final multiplicity (FFM), suppression of the jet-conversion photon pT distribution is observed. The results with FFM (as it is the most realistic situation) have been compared with high pT PHENIX photon data. It is found that the data are reproduced well if the isotropization time lies within 1.5 fm/c.

  14. Rapidity distribution of photons from an anisotropic quark-gluon plasma

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Lusaka; Roy, Pradip

    2010-05-01

    We calculate rapidity distribution of photons due to Compton and annihilation processes from quark gluon plasma with pre-equilibrium momentum-space anisotropy. We also include contributions from hadronic matter with late-stage transverse expansion. A phenomenological model has been used for the time evolution of hard momentum scale, phard(τ), and anisotropy parameter, ξ(τ). As a result of pre-equilibrium momentum-space anisotropy, we find significant modification of photons rapidity distribution. For example, with the fixed initial condition (FIC) free-streaming (δ=2) interpolating model we observe significant enhancement of photon rapidity distribution at fixed pT, where as for FIC collisionally broadened (δ=2/3) interpolating model the yield increases till y~1. Beyond that suppression is observed. With fixed final multiplicity (FFM) free-streaming interpolating model we predict enhancement of photon yield which is less than the case of FIC. Suppression is always observed for FFM collisionally broadened interpolating model.

  15. Scintillation of radio astronomical sources due to anisotropic inhomogeneities in the ionospheric plasma

    SciTech Connect

    Bezrodnyi, V.G.

    1988-02-01

    We have investigated the properties of scintillation of sources of cosmic radio emission due to inhomogeneities in the ionospheric F-region. The inhomogeneities are elongated along the geomagnetic field lines. We show that when the line of sight coincides with the magnetic field direction, we should observe an increase in the magnitude of the scintillation index. The amount of the increase, as well as the angular range in which it occurs, depend on the explicit shape of the spectrum of spatial scales of the inhomogeneities. We have given consideration to models which have been adopted in the literature for three-dimensional and two-dimensional anisotropy in the ionospheric turbulence. Based on this analysis, we propose a diagnostic method for the inhomogeneous ionospheric plasma. It is based on multifrequency measurements of the scintillation index of radio astronomical sources which culminate near the direction of the geomagnetic field lines at the latitude of the observing point. We establish the limits which are imposed on our proposed method because of the finite dimensions of the sources.

  16. Adiabatic-drift-loss modification of the electromagnetic loss-cone instability for anisotropic plasma

    NASA Astrophysics Data System (ADS)

    Juhl, B.; Treumann, R. A.

    1980-09-01

    Observation of the adiabatic behavior of energetic particle pitch-angle distributions in the magnetosphere in the past indicated the development of pronounced minima or drift-loss cones on the pitch-angle distributions centered at angles between particle velocity and magnetic field of approximately 90 deg in connection with storm-time changes in magnetospheric convection and magnetic field. Using a model of a drift-modified loss-cone distribution (MLCD) of the butterfly type, the linear stability of electromagnetic whistler or ion-cyclotron waves propagating parallel to the magnetic field has been investigated. The instability is shown to be quenched at high frequencies less than the marginally stable frequency, which is equal to A/(A + 1), where A is the thermal anisotropy. This quenching becomes stronger the higher are the respective parallel hot particle thermal velocity and cold plasma density. Particles around pitch-angles of approximately 90 deg are identified as generating electromagnetic cyclotron waves near the marginally stable frequency. It is concluded that the absence of electromagnetic VLF and ELF noise during times when MLCD develops is the result of the shift of the unstable spectrum to low frequencies.

  17. Alpha Heating and Burning Plasmas in Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Betti, R.; Christopherson, A. R.; Bose, A.; Woo, K. M.

    2016-05-01

    Assessing the degree to which fusion alpha particles contribute to the fusion yield is essential to understanding the onset of the thermal runaway process of thermonuclear ignition. It is shown that in inertial confinement fusion, the yield enhancement due to alpha particle heating (before ignition occurs) depends on the generalized Lawson parameter that can be inferred from experimental observables. A universal curve valid for arbitrary laser-fusion targets shows the yield amplification due to alpha heating for a given value of the Lawson parameter. The same theory is used to determine the onset of the burning plasma regime when the alpha heating exceeds the compression work. This result can be used to assess the performance of current ignition experiments at the National Ignition Facility.

  18. Inverse bremsstrahlung heating rate for dense plasmas in laser fields

    NASA Astrophysics Data System (ADS)

    Dey, R.; Roy, A. C.

    2013-07-01

    We report a theoretical analysis of inverse bremsstrahlung heating rate in the eikonal approximation. The present analysis is performed for a dense plasma using the screened electron-ion interaction potential for the ion charge state Zi = 1 and for both the weak and strong plasma screening cases. We have also compared the eikonal results with the first Born approximation (FBA) [M. Moll et al., New J. Phys. 14, 065010 (2012)] calculation. We find that the magnitudes of inverse bremsstrahlung heating rate within the eikonal approximation (EA) are larger than the FBA values in the weak screening case (κ = 0.03 a.u.) in a wide range of field strength for three different initial electron momenta (2, 3, and 4 a.u.). But for strong screening case (κ = 0.3 a.u.), the heating rates predicted by the two approximations do not differ much after reaching their maximum values. Furthermore, the individual contribution of photoemission and photoabsorption processes to heating rate is analysed for both the weak and strong screening cases. We find that the single photoemission and photoabsorption rates are the same throughout the field strength while the multiphoton absorption process dominates over the multiphoton emission process beyond the field strength ≈ 4×108 V/cm. The present study of the dependence of heating rate on the screening parameter ranging from 0.01 to 20 shows that whereas the heating rate predicted by the EA is greater than the FBA up to the screening parameter κ = 0.3 a.u., the two approximation methods yield results which are nearly identical beyond the above value.

  19. Ne IX line G-ratio in a non-Maxwellian and anisotropic plasma

    NASA Astrophysics Data System (ADS)

    Ferouani, A. K.; Inal, M. K.; Csanak, G.

    2013-04-01

    We have theoretically studied how the presence of a small proportion of energetic beam electrons mixed to a bulk of Maxwellian electrons in a hot plasma affects the temperature-dependent intensity ratio G = (x + y + z)/w of the helium-like triplet intercombination (x, y) and forbidden (z) lines to the singlet resonance line (w). By modelling the electron distribution function as a combination of a Maxwellian isotropic component and a monoenergetic beam component, detailed calculations of the G ratio of the Ne8 + lines have been performed for temperatures Te of the Maxwellian component and kinetic energies e0 of the beam component in the ranges 106-107 K and 1.5-25 keV, respectively. A magnetic sublevel-to-magnetic sublevel collisional-radiative model has been used for determining the populations of the upper magnetic sublevels of the four lines at an electron density below 1013 cm-3. Excitations from the ground 1s2 1S0 and metastable 1s2s 3S1 magnetic sublevels to the 1snl (n = 2-4) magnetic sublevels as well as the inner-shell ionization of the lithium-like ion in its ground level were taken into account. All basic atomic data, including the radiative transition probabilities and the collisional excitation and ionization cross sections, were computed using the flexible atomic code. It is found that the contribution of a 5% fraction of the beam component can reduce the G ratio by a factor of 30 at Te = 106 K and of 2.4 at Te = 3 × 106 K. Our calculations also indicate that the effect of directionality of the beam component on G is negligible for e0 above ˜10 keV and that for a given Te, G is practically insensitive to variations in e0 above ˜7 keV.

  20. Self-gravitating rotating anisotropic pressure plasma in presence of Hall current and electrical resistivity using generalized polytrope laws

    SciTech Connect

    Prajapati, R. P.; Chhajlani, R. K.; Soni, G. D.

    2008-06-15

    The effects of uniform rotation, finite electrical resistivity, electron inertia, and Hall current on the self-gravitational instability of anisotropic pressure plasma with generalized polytrope laws have been studied. A general dispersion relation is obtained with the help of the relevant linearized perturbed magnetohydrodynamic (MHD) equations incorporating the relevant contributions of various effects of the problem using the method of normal mode analysis. The general dispersion relation is further reduced for the special cases of rotation; i.e., parallel and perpendicular to the direction of the magnetic field. The longitudinal and transverse modes of propagation are discussed separately for investigation of condition of instability. The effects of rotation, Hall current, finite electron inertia, and polytropic indices are discussed on the gravitational, ''firehose,'' and ''mirror'' instabilities. The numerical calculations have been performed to obtain the dependence of the growth rate of the gravitational unstable mode on the various physical parameters involved. The finite electrical resistivity, rotation, and Hall current have a stabilizing influence on the growth rate of the unstable mode of wave propagation. The finite electrical resistivity removes the effect of magnetic field and polytropic index from the condition of instability in the transverse mode of propagation for both the cases of rotation. It is also found that the Jeans criterion of gravitational instability depends upon rotation, electron inertia, and polytropic indices. In the case of transverse mode of propagation with the axis of rotation parallel to the magnetic field, it is observed that the region of instability and the value of the critical Jeans wavenumber are larger for the Chew-Goldberger-Low set of equations in comparison with the MHD set of equations. The stability of the system is discussed by applying Routh-Hurwitz criterion. The inclusion of rotation or Hall current or both

  1. The Conversion of Large-Scale Turbulent Energy to Plasma Heat In Astrophysical Plasmas

    NASA Astrophysics Data System (ADS)

    Howes, Gregory

    2015-11-01

    Turbulence in space and astrophysical plasmas plays a key role in the conversion of the energy of violent events and instabilities at large scales into plasma heat. The turbulent cascade transfers this energy from the large scales at which the motions are driven down to small scales, and this essentially fluid process can be understood in terms of nonlinear wave-wave interactions. At sufficiently small scales, for which the dynamics is often weakly collisional, collisionless mechanisms damp the turbulent electromagnetic fluctuations, and this essentially kinetic process can be understood in terms of linear wave-particle interactions. In this talk, I will summarize the possible channels of the turbulent dissipation in a weakly collisional plasma, and present recent results from kinetic numerical simulations of plasma turbulence. Finally, I will discuss strategies for the definitive identification of the dominant dissipation channels using spacecraft measurements of turbulence in the solar wind.

  2. Versatile and Rapid Plasma Heating Device for Steel and Aluminum

    SciTech Connect

    Reddy, G.S.

    2006-03-14

    The main objective of the research was to enhance steel and aluminum manufacturing with the development of a new plasma RPD device. During the project (1) plasma devices were manufactured (2) testing for the two metals were carried out and (3) market development strategies were explored. Bayzi Corporation has invented a Rapid Plasma Device (RPD) which produces plasma, comprising of a mixture of ionized gas and free electrons. The ions, when they hit a conducting surface, deposit heat in addition to the convective heat. Two generic models called the RPD-Al and RPD-S have been developed for the aluminum market and the steel market. Aluminum melting rates increased to as high as 12.7 g/s compared to 3 g/s of the current industrial practice. The RPD melting furnace operated at higher energy efficiency of 65% unlike most industrial processes operating in the range of 13 to 50%. The RPD aluminum melting furnace produced environment friendly cleaner melts with less than 1% dross. Dross is the residue in the furnace after the melt is poured out. Cast ingots were extremely clean and shining. Current practices produce dross in the range of 3 to 12%. The RPD furnace uses very low power ~0.2 kWh/Lb to melt aluminum. RPDs operate in one atmosphere using ambient air to produce plasma while the conventional systems use expensive gases like argon, or helium in air-tight chambers. RPDs are easy to operate and do not need intensive capital investment. Narrow beam, as well as wide area plasma have been developed for different applications. An RPD was developed for thermal treatments of steels. Two different applications have been pursued. Industrial air hardening steel knife edges were subjected to plasma beam hardening. Hardness, as measured, indicated uniform distribution without any distortion. The biggest advantage with this method is that the whole part need not be heated in a furnace which will lead to oxidation and distortion. No conventional process will offer localized

  3. Transverse ion heating in multicomponent plasmas. [in ionosphere

    NASA Technical Reports Server (NTRS)

    Ashour-Abdalla, M.; Okuda, H.; Kim, S. Y.

    1987-01-01

    A new mechanism is proposed for plasma modes which can occur only in a multicomponent plasma and not in pure electron-ion plasma. The addition of ions creates a new instability near the ion-ion hybrid mode whose frequency is adequate for the wave to interact with oxygen ions. To study heating of ions (such as ionospheric oxygen ions) in presence of auroral electrons, several numerical simulations were carried out using a one-dimensional electrostatic code in a magnetic field. It was found that in the presence of electrons drifting along auroral field lines into the ionosphere, the ion-ion hybrid mode can be driven unstable when the electron drift speed is too small to excite the lower hybrid instability. Since the ion-ion mode has a smaller frequency than that of the lower hybrid waves, it can couple to the heavy ions, resulting in a substantial heating of heavy ions; on the other hand, because of their frequencies, the lower hybrid waves can accelerate only light ion species.

  4. Alpha-Heating and a Burning Plasma State

    NASA Astrophysics Data System (ADS)

    Hurricane, O. A.; Callahan, D. A.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Doeppner, T.; Barrios Garcia, M. A.; Haan, S.; Hinkel, D. E.; Berzak Hopkins, L. F.; Jones, O.; Kritcher, A. L.; Le Pape, S.; Ma, T.; Macphee, A.; Milovich, J.; Moody, J.; Pak, A.; Park, H.-S.; Patel, P. K.; Remington, B. A.; Robey, H. F.; Salmonson, J.; Springer, P. T.; Tommasini, R.

    2014-10-01

    L. R. BENEDETTI, D. BRADLEY, D. FITTINGHOFF, N. IZUMI, S. KHAN, R. TOWN (LLNL) G. GRIM, N. GULER, G. KYRALA, F. MERRILL, C. WILDE, P. VOLEGOV (LANL) High-foot implosions show net fuel gains and significant alpha-heating [Hurricane et al., Nature 506, 343 (2014)] using a per shot analysis of NIF data with a static reconstruction of the implosion energetics [e.g. Cerjan et al., PoP 20 (2013)]. Inference of the alpha-heating contribution to the yield is made using a simulation database of DT implosions and the one-to-one correspondence of yield amplification and normalized Lawson criteria [Patel et al., APS-DPP, (2013); Patel et al. this conf.]. A dynamic semi-analytic model for the DT self-heating rate can be constructed that can more directly be used, with data, to determine the degree of bootstrapping occuring in implosions. Here we propose that the suite of high-foot data demonstrate a scaling of fusion yield performance versus energy absorbed that provides an alternate proof of significant alpha-particle self-heating. This analysis shows that recent high-foot implosions are alpha-heating dominated and thus have achieved a `burning-plasma' state. Work performed under the auspices of U.S. Dept. of Energy by LLNL under Contract DE-AC52-07NA27344.

  5. The effect of plasma shear flow on drift Alfven instabilities of a finite beta plasma and on anomalous heating of ions by ion cyclotron turbulence

    NASA Astrophysics Data System (ADS)

    Jo, Young Hyun; Lee, Hae June; Mikhailenko, Vladimir V.; Mikhailenko, Vladimir S.

    2016-01-01

    It was derived that the drift-Alfven instabilities with the shear flow parallel to the magnetic field have significant difference from the drift-Alfven instabilities of a shearless plasma when the ion temperature is comparable with electron temperature for a finite plasma beta. The velocity shear not only modifies the frequency and the growth rate of the known drift-Alfven instability, which develops due to the inverse electron Landau damping, but also triggers a combined effect of the velocity shear and the inverse ion Landau damping, which manifests the development of the ion kinetic shear-flow-driven drift-Alfven instability. The excited unstable waves have the phase velocities along the magnetic field comparable with the ion thermal velocity, and the growth rate is comparable with the frequency. The development of this instability may be the efficient mechanism of the ion energization in shear flows. The levels of the drift--Alfven turbulence, resulted from the development of both instabilities, are determined from the renormalized nonlinear dispersion equation, which accounts for the nonlinear effect of the scattering of ions by the electromagnetic turbulence. The renormalized quasilinear equation for the ion distribution function, which accounts for the same effect of the scattering of ions by electromagnetic turbulence, is derived and employed for the analysis of the ion viscosity and ions heating, resulted from the interactions of ions with drift-Alfven turbulence. In the same way, the phenomena of the ion cyclotron turbulence and anomalous anisotropic heating of ions by ion cyclotron plasma turbulence has numerous practical applications in physics of the near-Earth space plasmas. Using the methodology of the shearing modes, the kinetic theory of the ion cyclotron turbulence of the plasma with transverse current with strong velocity shear has been developed.

  6. Alpha Heating and Burning Plasmas in Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Christopherson, A. R.

    2015-11-01

    In inertial confinement fusion, a spherical capsule of cryogenic DT is accelerated inward at a high velocity. Near stagnation, a dense hot spot is formed where the deuterium and tritium ions begin to fuse, creating a 3.5-MeV alpha particle per reaction. These alpha particles deposit energy back into the plasma, thereby increasing the pressure, temperature, and reaction rate. This feedback process is called ``alpha heating,'' and ignition is a direct consequence of this thermal instability. The onset of a burning-plasma regime occurs when the total alpha-particle energy produced exceeds the shell compression work. Using an analytic compressible-shell model for the implosion, it is found that the onset of the burning-plasma regime is a unique function of the neutron yield enhancement caused by alpha particles for any target, direct or indirect drive. This yield enhancement can then be inferred from experimentally measureable quantities, such as the Lawson parameter. From this analysis, the onset of a burning plasma occurs at yields exceeding 50 kJ for implosions at the National Ignition Facility. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and DE-FC02-04ER54789 (Fusion Science Center).

  7. Intermittent dissipation and heating in 3D kinetic plasma turbulence

    NASA Astrophysics Data System (ADS)

    Wan, M.; Matthaeus, W. H.; Roytershteyn, V.; Karimabadi, H.; Parashar, T.; Wu, P.; Shay, M. A.

    2014-12-01

    The nature of collisionless dissipation has been hotlydebated in recent years, with alternative ideas posed interms of various wave modes, such as kinetic Alfven waves,whistlers, linear Vlasov instabilities, cyclotron resonance,and Landau damping. Here we use large scale, fully kinetic3D simulations of collisionless plasma turbulence which showthe development of turbulence characterized by sheet-likecurrent density structures spanning a range of scales.We present evidence that these structures are sites for heatingand dissipation, and that stronger current structures signifyhigher dissipation rates. The analyses focus on quantities such as J.E, electron and proton temperatures, and PVI of the magnetic field. Evidently, kinetic scale plasma,like magnetohydrodynamics, becomes intermittent due tocurrent sheet formation, leading to the expectationthat heating and dissipation in astrophysical and space plasmasmay be highly nonuniform. Comparison with previousresults from 2D kinetic simulations, as well as high frequencysolar wind observational data will also be discussed.

  8. RFQ (radio-frequency quadrupole) accelerators for heating thermonuclear plasmas

    SciTech Connect

    Stokes, R.H.; Wangler, T.P.; Crandall, K.R.

    1987-01-01

    The radio-frequency quadrupole (RFQ) accelerator has been developed to generate high-current ion beams for a wide variety of applications. It has also been suggested that this type of accelerator could be used to produce megawatt ion beams to heat thermonuclear reactor plasmas. For a tokamak reactor, an RFQ accelerator can be designed to provide negative deuterium ions that are neutralized before injection through the tokamak magentic field. Also, it may be possible to use singly charged, positive, heavier ions that trasverse the magnetic field with minimal deflection and then become multiply ionized upon striking the tokamak plasma. We present preliminary RFQ beam-dynamics designs for both deuterium and oxygen ions.

  9. Plasma-ion Induced Sputtering and Heating of Titan's Atmosphere

    NASA Astrophysics Data System (ADS)

    Johnson, R. E.; Tucker, O. J.

    2007-05-01

    Titan is unique among the outer solar system icy satellites in having an atmosphere with a column density about ten times that of the Earth's atmosphere and an atmospheric mass to solid mass ratio comparable to that of Venus. Atmospheres equivalent in size to that at Titan would have been removed from the icy Galilean satellites by the plasma trapped in the Jovian magnetosphere (Johnson 2004). Therefore, the use of Cassini data to determine the present erosion rate of Titan's atmosphere provides an important end point for studying the erosion and heating of planetary and satellite atmospheres by an ambient plasma. In this paper we describe the deposition of energy, the erosion and the expansion of the upper atmosphere of Titan using Direct Simulation Monte Carlo models (Shematovich et al. 2003; Michael et al. 2005; Michael and Johnson 2005). These calculations are used to calibrate semi-empirical models of atmospheric sputtering (Johnson 1994) that are used to interpret Cassini data at Titan. Using a number of plasma conditions, the temperature and density vs. altitude above the exobase and the rate of escape are calculated. References: Johnson, R.E. "Plasma-induced Sputtering of an Atmosphere" in Space Science Reviews 69 215-253 (1994). Johnson. R.E., " The magnetospheric plasmadriven evolution of satellite atmospheres" Astrophys. J. 609, L99-L102 (2004). Michael, M. and R.E. Johnson, "Energy deposition of pickup ions and heating of Titan's atmosphere", Planetary & Space Sci.53, 1510-1514 (2005). Michael M., R.E. Johnson, F. Leblanc, M. Liu, J.G. Luhmann, and V.I. Shematovich, "Ejection of nitrogen from Titan's atmosphere by magnetospheric ions and pick-up ions", Icarus 175, 263-267 (2005). Shematovich, V.I., R.E. Johnson, M. Michael, and J.G. Luhmann, "Nitrogen loss from Titan", JGR 108, No. E8, 5087, doi:10.1029/2003JE002094 (2003).

  10. Identification of higher frequency plasma waves inside a Kelvin-Helmholtz vortex responsible for plasma heating and mixing

    NASA Astrophysics Data System (ADS)

    Moore, T.; Nykyri, K.; Dimmock, A. P.

    2014-12-01

    The magnetopause marks the boundary between the shocked solar wind and magnetospheric plasma. Understanding the dynamics of the plasma processes at the magnetopause boundary is crucial to the study of plasma transport into the magnetosphere. Previous studies have shown that there exists a temperature asymmetry in the plasma sheet. During northward IMF, the cold component ions are 30-40% hotter in the dawn flank plasma sheet compared to the dusk flank. However, the mechanisms responsible are still not entirely clear. Recent work has shown that reconnection in Kelvin-Helmholtz (KH) vortices can transport plasma into the magnetosphere. Previous studies have also shown that mode conversion at the magnetopause can generate kinetic Alfvén wave activity. Both magnetic reconnection and plasma wave activity can heat plasma. For the first time we have determined from observations the dispersion relation of higher frequency waves responsible for plasma mixing and heating within a KH vortex.

  11. Plasma heating with multi-MeV neutral atom beams

    SciTech Connect

    Grisham, L.R.; Post, D.E.; Mikkelsen, D.R.; Eubank, H.P.

    1981-10-01

    We explore the utility and feasibility of neutral beams of greater than or equal to 6 AMU formed from negative ions, and also of D/sup 0/ formed from D/sup -/. The negative ions would be accelerated to approx. 1 to 2 MeV/AMU and neutralized, whereupon the neutral atoms would be used to heat and, perhaps, to drive current in magnetically confined plasmas. Such beams appear feasible and offer the promise of significant advantages relative to conventional neutral beams based on positive deuterium ions at approx. 150 keV.

  12. Application of rf-thruster technique for fusion plasma heating

    NASA Astrophysics Data System (ADS)

    Freisinger, J.; Loeb, H. W.

    On the basis of RF ion thruster devices, a family of RF injector generators (RIGs) for the heating of fusion plasmas up to the temperature of thermonuclear burn has been developed. Hydrogen ion beams of 10-40 amps can be accelerated by means of the RIGs to 30 kV, so that ion beam densities of more than 250 mA/sq cm are achievable at uniform profiles within only 1 deg of divergence angle. The use of electrodeless quartz ionizers yields a very high atomic ion fraction, low admixture of impurities, long lifetime, high reliability, simple mechanical elements, and easy control.

  13. Plasma heating and current drive using intense, pulsed microwaves

    SciTech Connect

    Cohen, B.I.; Cohen, R.H.; Nevins, W.M.; Rognlien, T.D.; Bonoli, P.T.; Porkolab, M.

    1988-01-01

    The use of powerful new microwave sources, e.g., free-electron lasers and relativistic gyrotrons, provide unique opportunities for novel heating and current-drive schemes in the electron-cyclotron and lower-hybrid ranges of frequencies. These high-power, pulsed sources have a number of technical advantages over conventional, low-intensity sources; and their use can lead to improved current-drive efficiencies and better penetration into a reactor-grade plasma in specific cases. The Microwave Tokamak Experiment at Lawrence Livermore National Laboratory will provide a test for some of these new heating and current-drive schemes. This paper reports theoretical progress both in modeling absorption and current drive for intense pulses and in analyzing some of the possible complications that may arise, e.g., parametric instabilities and nonlinear self-focusing. 22 refs., 9 figs., 1 tab.

  14. Multi-scale gyrokinetic simulation of tokamak plasmas: enhanced heat loss due to cross-scale coupling of plasma turbulence

    NASA Astrophysics Data System (ADS)

    Howard, N. T.; Holland, C.; White, A. E.; Greenwald, M.; Candy, J.

    2016-01-01

    The transport of heat in laboratory and astrophysical plasmas is dominated by the complex nonlinear dynamics of plasma turbulence. In magnetically confined plasmas used for fusion energy research, turbulence is responsible for cross-field transport that limits the performance of tokamak reactors. We report a set of novel gyrokinetic simulations that capture ion and electron-scale turbulence simultaneously, revealing the dynamics of cross-scale energy transfer and zonal flow modification that give rise to heat losses. Multi-scale simulations are required to match experimental ion and electron heat fluxes and electron profile stiffness, establishing the applicability of the newly discovered physics to experiment. Importantly, these results provide a likely explanation for the loss of electron heat from tokamak plasmas, the ‘great unsolved problem’ (Bachelor et al (2007 Plasma Sci. Technol. 9 312-87)) in plasma turbulence and the projected dominant loss channel in ITER.

  15. Heat capacity measurements on UBe13 in rotated magnetic fields: Anisotropic response in the normal state and absence of nodal quasiparticles

    NASA Astrophysics Data System (ADS)

    Shimizu, Yusei; Kittaka, Shunichiro; Sakakibara, Toshiro; Haga, Yoshinori; Yamamoto, Etsuji; Amitsuka, Hiroshi; Tsutsumi, Yasumasa; Machida, Kazushige

    2016-02-01

    In order to gain insight into the superconducting (SC) gap of UBe13, we studied its quasiparticle excitations by means of heat-capacity measurements. Quite unexpectedly, we found the isotropic C(H) ∝ H behavior in low fields at low temperatures, implying the absence of nodal quasiparticle excitations. This result indicates that the SC gap in UBe13 is fully open over the Fermi surfaces. Furthermore, we observed a characteristic oscillation of heat capacity both in the SC and non-Fermi-liquid normal states above ∼2 T, and the angular variation of heat capacity possibly originates from anisotropic magnetic response of the heavy-electron state. Our result regarding the low-energy quasiparticle excitations in the SC and normal states will be a clue to understand the unusual nature of UBe13.

  16. Plasma-ion-induced sputtering and heating of Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Johnson, R. E.; Michael, M.; Tucker, O. J.; Shematovich, V. I.; Luhmann, J. H.; Ledvina, S. A.

    Titan is unique among the outer solar system icy satellites in having an atmosphere with a column density about ten times that of the Earth's atmosphere and an atmosphere mass to solid mass ratio comparable to that of Venus. Atmospheres equivalent in size to that at Titan would have been removed from the icy Galilean satellites by the plasma trapped in the Jovian magnetosphere (Johnson 2004). Therefore, the fact that data from the Cassini spacecraft can be used to determine the present erosion rate of Titan's atmosphere by the plasma trapped in Saturn's magnetosphere provides an exciting end point for studying the erosion and heating of planetary and satellite atmospheres by an ambient plasma. In this paper we describe the deposition of energy, the erosion and the expansion of the upper atmosphere of Titan using Direct Simulation Monte Carlo models (Shematovich et al. 2003; Michael et al. 2005; Michael and Johnson 2005). These calculations are used to calibrate semi-empirical models of atmospheric sputtering (Johnson 1994) that can, in principal, be employed in interpreting Cassini data at Titan. It is shown that the globally averaged flux of magnetospheric and pickup ions deposit more energy in Titan's upper atmosphere than solar radiation. Using a number of plasma conditions, the temperature and density vs. altitude above the exobase and the rate of escape are calculated and compared to available Cassini data. References: Johnson, R.E. "Plasma-induced Sputtering of an Atmosphere" in Space Science Reviews 69 215-253 (1994). Johnson. R.E., " The magnetospheric plasma- driven evolution of satellite atmospheres" Astrophys. J. 609, L99-L102 (2004). Michael, M. and R.E. Johnson, "Energy deposition of pickup ions and heating of Titan's atmosphere", Planetary & Space Sci.53, 1510-1514 (2005). Michael M., R.E. Johnson, F. Leblanc, M. Liu, J.G. Luhmann, and V.I. Shematovich, "Ejection of nitrogen from Titan's atmosphere by magnetospheric ions and pick-up ions", Icarus 175

  17. Fabrication and local laser heating of freestanding Ni{sub 80}Fe{sub 20} bridges with Pt contacts displaying anisotropic magnetoresistance and anomalous Nernst effect

    SciTech Connect

    Brandl, F.; Grundler, D.

    2014-04-28

    In spin caloritronics, ferromagnetic samples subject to relatively large in-plane temperature gradients ∇T have turned out to be extremely interesting. We report on a preparation technique that allows us to create freely suspended permalloy/Pt hybrid structures where a scanning laser induces ∇T on the order of a few K/μm. We observe both the anisotropic magnetoresistance at room temperature and the magnetic field dependent anomalous Nernst effect under laser heating. The technique is promising for the realization of device concepts considered in spin caloritronics based on suspended ferromagnetic nanostructures with electrical contacts.

  18. Accelerating piston action and plasma heating in high-energy density laser plasma interactions

    NASA Astrophysics Data System (ADS)

    Levy, M. C.; Wilks, S. C.; Baring, M. G.

    2013-03-01

    In the field of high-energy density physics (HEDP), lasers in both the nanosecond and picosecond regimes can drive conditions in the laboratory relevant to a broad range of astrophysical phenomena, including gamma-ray burst afterglows and supernova remnants. In the short-pulse regime, the strong light pressure (>Gbar) associated ultraintense lasers of intensity I > 1018 W/cm2 plays a central role in many HEDP applications. Yet, the behavior of this nonlinear pressure mechanism is not well-understood at late time in the laser-plasma interaction. In this paper, a more realistic treatment of the laser pressure 'hole boring' process is developed through analytical modeling and particle-in-cell simulations. A simple Liouville code capturing the phase space evolution of ponderomotively-driven ions is employed to distill effects related to plasma heating and ion bulk acceleration. Taking into account these effects, our results show that the evolution of the laser-target system encompasses ponderomotive expansion, equipartition, and quasi-isothermal expansion epochs. These results have implications for light piston-driven ion acceleration scenarios, and astrophysical applications where the efficiencies of converting incident Poynting flux into bulk plasma flow and plasma heat are key unknown parameters.

  19. Ion cyclotron range of frequencies heating and flow generation in deuterium{endash}tritium plasmas

    SciTech Connect

    Wilson, J.R.; Bell, R.E.; Bernabei, S.; Hill, K.; Hosea, J.C.; LeBlanc, B.; Majeski, R.; Nazikian, R.; Ono, M.; Phillips, C.K.; Schilling, G.; von Goeler, S.; Bush, C.E.; Hanson, G.R.

    1998-05-01

    Recent radio-frequency heating experiments on the Tokamak Fusion Test Reactor (TFTR) [Hawryluk {ital et al.}, Plasma Phys. Controlled Fusion {bold 33}, 1509 (1991)] have focused on developing tools for both pressure and current profile control in deuterium{endash}tritium (DT) plasmas. A new antenna was added to investigate pressure profile control utilizing direct ion Bernstein wave (IBW) heating. This was the first time direct IBW heating was explored on TFTR. Plasma heating and driven poloidal flows are observed. Previously heating and current drive via mode-converted IBW waves had been demonstrated in non-DT plasmas but efforts in DT plasmas had been unsuccessful. This lack of success had been ascribed to the presence of a small {sup 7}Li minority ion population. In the most recent experiments {sup 6}Li was used exclusively for machine conditioning and mode-conversion heating consistent with theory is now observed in DT plasmas. {copyright} {ital 1998 American Institute of Physics.}

  20. Ultra-rapid plasma freezing with halocarbon heat transfer liquids

    SciTech Connect

    Coelho, P.H.; Comerchero, V.

    1988-03-15

    A process of freezing plasma is described comprising the steps of exposing thin wall containers of plasma to be frozen to direct contact with a heat transfer liquid selected from the group consisting of the chlorofluorocarbon 1,1,2 trichloro-1,2,2, trifluoro-ethane (CFC 113) and mixtures of the chlorofluorocarbon 1,1,2 trichloro-1,2,2, trifluoro-ethane (Freon 113) and at least one of the fluorocarbons perfluoropentane (C/sub 5/F/sub 12/), perfluorohexane (C/sub 6/F/sub 14/), perfluoromethylcyclohexane (C/sub 7/F/sub 14/), perfluoroheptane (C/sub 7/F/sub 16/), perfluoromonomethyldimethylcyclohexanes (C/sub 7/F/sub 14/C/sub 8/F/sub 16/), perfluorodecalin isomers (C/sub 10/F/sub 18/), mixed perfluorodecalin and methyldecalin isomers (C/sub 10/F/sub 18/+C/sub 11/F/sub 20/), and perfluorinatd polyethers ((OCF(CF/sub 3/)CF/sub 2/)/sub n/ - (OCF/sub 2/)/sub m/, and maintaining the liquid at a temperature sufficiently low enough to freeze the plasma in the desired amount of time.

  1. Negative specific heat of a magnetically self-confined plasma torus

    PubMed Central

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

    2003-01-01

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

  2. Electron heating in capacitively coupled RF plasmas: a unified scenario

    NASA Astrophysics Data System (ADS)

    Brinkmann, Ralf Peter

    2016-02-01

    Electron heating in radio-frequency capacitively coupled plasmas (RF-CCP) is studied from first principles. The starting points are the electron equations of continuity and motion, with ionization neglected but electric and pressure forces and elastic collisions with the neutral background taken into account. Poisson’s equation self-consistently calculates the electric field; the ion density is assumed as a given. Postulating that the Debye length {λ\\text{D}} is small compared to the sheath length scale l and the applied frequency {ω\\text{RF}} is small compared to the electron plasma frequency {ω\\text{pe}} , an asymptotic expansion in the smallness parameter ε ={λ\\text{D}}/l∼ {ω\\text{RF}}/{ω\\text{pe}} is conducted. As has been demonstrated before (Brinkmann 2015 Plasma Sources Sci. Technol. 24 064002), this ansatz gives an expression—the smooth step model (SSM)—which yields (i) the space charge field in the unipolar region, (ii) the generalized Ohmic field in the ambipolar region, and (iii) a smooth interpolation for the rapid transition in between. Using the SSM and formulas for the electron density and the electron flux, expressions for the electric force and the electric power density are established which hold up to O≤ft(ε \\right) . Integrating over the sheath and taking the phase average, a representation for the total dissipated power is found as a sum of four physically distinct contributions. All terms correspond to electron heating mechanisms which are (explicitly or implicitly) already known but were so far discussed only within mutually incompatible frameworks.

  3. Advanced simulation of electron heat transport in fusion plasmas

    SciTech Connect

    Lin, Zhihong; Xiao, Y.; Klasky, Scott A; Lofstead, J.

    2009-01-01

    Electron transport in burning plasmas is more important since fusion products first heat electrons. First-principles simulations of electron turbulence are much more challenging due to the multi-scale dynamics of the electron turbulence, and have been made possible by close collaborations between plasma physicists and computational scientists. The GTC simulations of collisionless trapped electron mode (CTEM) turbulence show that the electron heat transport exhibits a gradual transition from Bohm to gyroBohm scaling when the device size is increased. The deviation from the gyroBohm scaling can be induced by large turbulence eddies, turbulence spreading, and non-diffusive transport processes. Analysis of radial correlation function shows that CTEM turbulence eddies are predominantly microscopic but with a significant tail in the mesoscale. A comprehensive analysis of kinetic and fluid time scales shows that zonal flow shearing is the dominant decorrelation mechanism. The mesoscale eddies result from a dynamical process of linear streamers breaking by zonal flows and merging of microscopic eddies. The radial profile of the electron heat conductivity only follows the profile of fluctuation intensity on a global scale, whereas the ion transport tracks more sensitively the local fluctuation intensity. This suggests the existence of a nondiffusive component in the electron heat flux, which arises from the ballistic radial E x B drift of trapped electrons due to a combination of the presence of mesoscale eddies and the weak de-tuning of the toroidal precessional resonance that drives the CTEM instability. On the other hand, the ion radial excursion is not affected by the mesoscale eddies due to a parallel decorrelation, which is not operational for the trapped electrons because of a bounce averaging process associated with the electron fast motion along magnetic field lines. The presence of the nondiffusive component raises question on the applicability of the usual

  4. Advanced Simulation of Electron Heat Transport in Fusion Plasmas

    SciTech Connect

    Lin, Z.; Xiao, Y.; Holod, I.; Zhang, W. L.; Deng, Wenjun; Klasky, Scott A; Lofstead, J.; Kamath, Chandrika; Wichmann, Nathan

    2009-01-01

    Electron transport in burning plasmas is more important since fusion products first heat electrons. First-principles simulations of electron turbulence are much more challenging due to the multi-scale dynamics of the electron turbulence, and have been made possible by close collaborations between plasma physicists and computational scientists. The GTC simulations of collisionless trapped electron mode (CTEM) turbulence show that the electron heat transport exhibits a gradual transition from Bohm to gyroBohm scaling when the device size is increased. The deviation from the gyroBohm scaling can be induced by large turbulence eddies, turbulence spreading, and non-diffusive transport processes. Analysis of radial correlation function shows that CTEM turbulence eddies are predominantly microscopic but with a significant tail in the mesoscale. A comprehensive analysis of kinetic and fluid time scales shows that zonal flow shearing is the dominant decorrelation mechanism. The mesoscale eddies result from a dynamical process of linear streamers breaking by zonal flows and merging of microscopic eddies. The radial profile of the electron heat conductivity only follows the profile of fluctuation intensity on a global scale, whereas the ion transport tracks more sensitively the local fluctuation intensity. This suggests the existence of a nondiffusive component in the electron heat flux, which arises from the ballistic radial E x B drift of trapped electrons due to a combination of the presence of mesoscale eddies and the weak de-tuning of the toroidal precessional resonance that drives the CTEM instability. On the other hand, the ion radial excursion is not affected by the mesoscale eddies due to a parallel decorrelation, which is not operational for the trapped electrons because of a bounce averaging process associated with the electron fast motion along magnetic field lines. The presence of the nondiffusive component raises question on the applicability of the usual

  5. On the different regimes of gas heating in air plasmas

    NASA Astrophysics Data System (ADS)

    Pintassilgo, Carlos D.; Guerra, Vasco

    2015-10-01

    Simulations of the gas temperature in air (N2-20%O2) plasma discharges are presented for different values of the reduced electric field, E/N g, electron density n e, pressure and tube radius. This study is based on the solutions to the time-dependent gas thermal balance in a cylindrical geometry coupled to the electron, vibrational and chemical kinetics, for E/{{N}\\text{g}}=50 and 100 Td (1 Td = 10-17 V cm2), 109  ⩽  n e  ⩽  1011 cm-3, pressure in the range 1-20 Torr, and also considering different tube radius, 0.5, 1 and 1.5 cm. The competing role of different gas heating mechanisms is discussed in detail within the time range 0.01-100 ms. For times below 1 ms, gas heating occurs from O2 dissociation by electron impact through pre-dissociative excited states, e + O2  →  e + \\text{O}2*   →  e + 2O(3P) and …  →  e + O(3P) + O(1D), as well as through the quenching of N2 electronically excited states by O2. For longer times, simulation results show that gas heating comes from processes N(4S) + NO(X)  →  N2(X, v ~ 3) + O, N2(A) + O  →  NO(X) + N(2D), V-T N2-O collisions and the recombination of oxygen atoms at the wall. Depending on the given E/N g and n e values, each one of these processes can be an important gas-heating channel. The contribution of V-T N2-O exchanges to gas heating is important in the analysis of the gas temperature for different pressures and values of the tube radius. A global picture of these effects is given by the study of the fraction of the discharge power spent on gas heating, which is always ~15%. The values for the fractional power transferred to gas heating from vibrational and electronic excitation are also presented and discussed.

  6. Radio Frequency Field Calculations for Plasma Heating Simulations in VASIMR

    NASA Astrophysics Data System (ADS)

    Ilin, A. V.; Díaz, F. R. Chang; Squire, J. P.; Carter, M. D.

    2002-01-01

    (VASIMR)1 is plasma heating by ion-cyclotron RF heating (ICRF). Mathematical simulation helps to design an ICRF antenna, i.e. make maximal absorption of RF power into the plasma in the resonance area. Another goal of a particle simulation is design of a magnetic nozzle and optimize the performance of VASIMR2. field in the plasma, 2) ion density and velocity, 3) ion-cyclotron radio-frequency electromagnetic field. The assumptions of quasineutral and collisionless plasma are based on the range of operating VASIMR parameters. Carlo simulations for systems of million of particles in a reasonable time and without the need for a powerful supercomputer. The particle to grid weighting method is used for calculating the ion density, which is used for recalculation of the electric potential and RF field. dimensional problem to a weighted sum over two-dimensional solutions. Absorption is introduced in the cold plasma model by adding an imaginary collision frequency to the RF driven frequency, which is equivalent to adding an imaginary particle mass in the dielectric tensor elements. static and RF fields using the VASIMR code2. The VASIMR and EMIR codes are then iterated to estimate the ICRF effects on the plasma density. The iteration is performed by calculating the RF fields with the EMIR code, and using these fields to follow nonlinear ion trajectories with the VASIMR code on the gyro-frequency time scale. The ion trajectories are used to generate RF power absorption values and a density input for the next EMIR calculation. The codes are iterated until the density profile becomes reasonably stable, then the collisional absorption parameter in the EMIR code is adjusted and the iteration is continued until the power deposited by the RF system matches the power absorbed by the ion trajectories in a global sense. electric field. The solved algebraic system of equations is represented by ill-conditioned 18-diagonal matrix with complex elements. Since early development of the

  7. Plasma-ion-induced Sputtering And Heating Of Titan'S Atmosphere

    NASA Astrophysics Data System (ADS)

    Tucker, Orenthal J.

    2006-09-01

    Plasma-ion-induced sputtering and heating of Titan's atmosphere O.J. Tucker (1), R.E. Johnson (1), M. Michael (1), V.I. Shematovich (1,2) J.H. Luhmann (3), S.A. Ledvina (3) (1) University of Virginia, Charlottesville, VA 22904, USA (2) Institute of Astronomy RAS, Moscow 109017, Russia, (3) University of California, Berkeley, CA 94720, USA Titan is unique among the outer solar system icy satellites in having an atmosphere with a column density about ten times that of the Earth's atmosphere. Atmospheres equivalent in size similar to that at Titan would have been removed from the icy Galilean satellites by the plasma trapped in the Jovian magnetosphere (Johnson 2004). In this paper we describe the deposition of energy, the erosion and the expansion of the upper atmosphere of Titan using Direct Simulation Monte Carlo models (Shematovich et al. 2003; Michael et al. 2005). These calculations are used to calibrate semi-empirical models of atmospheric sputtering (Johnson 1994) that can be employed in interpreting Cassini data at Titan. It is shown that the globally averaged flux of magnetospheric and pickup ions deposit more energy in Titan's upper atmosphere than solar radiation. Using a number of plasma conditions, the temperature and density vs. altitude above the exobase and the rate of escape are calculated and compared to available Cassini data. References: Johnson, R.E. "Plasma-induced Sputtering of an Atmosphere" in Space Science Reviews 69 215-253 (1994). Johnson. R.E., “ The magnetospheric plasma-driven evolution of satellite atmospheres” Astrophys. J. 609, L99-L102 (2004). Michael M., R.E. Johnson, F. Leblanc, M. Liu, J.G. Luhmann, and V.I. Shematovich, "Ejection of nitrogen from Titan's atmosphere by magnetospheric ions and pick-up ions", Icarus 175, 263-267 (2005). Shematovich, V.I., R.E. Johnson, M. Michael, and J.G. Luhmann,"Nitrogen loss from Titan", JGR 108, No. E8, 5087, doi:10.1029/2003JE002094 (2003). 1

  8. Plasma Heating and Current Drive for Fusion Reactors

    NASA Astrophysics Data System (ADS)

    Holtkamp, Norbert

    2010-02-01

    ITER (in Latin ``the way'') is designed to demonstrate the scientific and technological feasibility of fusion energy. Fusion is the process by which two light atomic nuclei combine to form a heavier one and thus release energy. In the fusion process two isotopes of hydrogen - deuterium and tritium - fuse together to form a helium atom and a neutron. Thus fusion could provide large scale energy production without greenhouse effects; essentially limitless fuel would be available all over the world. The principal goals of ITER are to generate 500 megawatts of fusion power for periods of 300 to 500 seconds with a fusion power multiplication factor, Q, of at least 10. Q >= 10 (input power 50 MW / output power 500 MW). In a Tokamak the definition of the functionalities and requirements for the Plasma Heating and Current Drive are relevant in the determination of the overall plant efficiency, the operation cost of the plant and the plant availability. This paper summarise these functionalities and requirements in perspective of the systems under construction in ITER. It discusses the further steps necessary to meet those requirements. Approximately one half of the total heating will be provided by two Neutral Beam injection systems at with energy of 1 MeV and a beam power of 16 MW into the plasma. For ITER specific test facility is being build in order to develop and test the Neutral Beam injectors. Remote handling maintenance scheme for the NB systems, critical during the nuclear phase of the project, will be developed. In addition the paper will give an overview over the general status of ITER. )

  9. Isotopic mass and alpha heating effects in TFTR DT plasmas

    SciTech Connect

    Budny, R.V.; Bell, M.G.; Mansfield, D.K.

    1994-09-01

    Sets of similar TFTR discharges with varying amounts of D and T are compared. The T content is altered by varying the mix of D and T NBI at approximately constant total NBI power. The total plasma current, toroidal field, central Z{sub eff}, and wall conditions are very similar in each set. The electron density profiles are approximately similar. The sets contain pairs of discharges with D-only and DT-NBI. Several sets also contain discharges with T-only NBI. The discharges are analyzed using the TRANSP plasma analysis code. Good agreement with measured parameters is achieved. Profiles are computed for the isotopic mass of the hydrogenic thermal species A, and for the hydrogenic thermal plus beam species A{sub tot}. Their volume averages increase approximately linearly as the fraction of T-NBI power increases, and they are slightly peaked for DT and T-only NBI discharges. The total energy and the total energy confinement time increase approximately linearly with A{sub tot} up to 30%. The beam fraction of the total energy at 0.5 sec of NBI remains relatively constant, {approx} 40--50% as A{sub tot} varies. The thermal ion fraction increases slightly, and the electron fraction decreases. The isotopic and alpha heating effects contribute in roughly equal amounts to the increase in central T{sub e}.

  10. Glass Strengthening via High-Intensity Plasma-Arc Heating

    SciTech Connect

    Wereszczak, Andrew A; Harper, David C; Duty, Chad E; Patel, P

    2010-01-01

    The use of a high-intensity plasma-arc lamp was used to irradiate the surface of soda-lime silicate glass tiles to determine if an increase in strength could be achieved. The lamp had a power density of 3500 W/cm2, a processing area of 1 cm x 10 cm, irradiated near-infrared heating at a wavelength between 0.2 1.4 m, and was controlled to unidirectionally sweep across 50-mm-square tiles at a constant speed of 8 mm/s. Ring-on-ring (RoR) equibiaxial flexure and 4 pt uni-directional flexure testings of entire tiles were used to measure and compare failure stress distributions of treated and untreated glass. Even with non-optimized processing conditions, RoR failure stress increased by approximately 25% and the 4 pt bend failure stress increased by approximately 65%. Strengthening was due to a fire-polishing-like mechanism. The arc-lamp heat-treatment caused the location of the strength-limiting flaws in the 4-pt-bend tiles to change; namely, failure initiation occurred on the gage section surface for the treated glass whereas it occurred at a gage section edge for the untreated. Arc-lamp heat-treatment is attractive not only because it provides strengthening, but because it can (non-contact) process large amounts of glass quickly and inexpensively, and is a process that either a glass manufacturer or end-user can readily employ.

  11. Thermodynamics of the interconversion of heat and work via plasma electric fields

    SciTech Connect

    Avinash, K.

    2010-12-15

    Thermodynamics of a system where a group of cold charged particles locally confined in a volume V{sub P} within a warm plasma of temperature T and volume V (V{sub P}plasma. The interconversion of plasma heat and mechanical work via isothermal compression/expansion of plasma electric field (associated with charged particles) in a plasma heat pump and ES heat engine cycle is demonstrated. The efficiency of the plasma heat pump is discussed in terms of its power efficiency {eta}{sub P} and is shown to be close to unity

  12. Simultaneous Measurement of Thermal Diffusivity and Thermal Conductivity by Means of Inverse Solution for One-Dimensional Heat Conduction (Anisotropic Thermal Properties of CFRP for FCEV)

    NASA Astrophysics Data System (ADS)

    Kosaka, Masataka; Monde, Masanori

    2015-11-01

    For safe and fast fueling of hydrogen in a fuel cell electric vehicle at hydrogen fueling stations, an understanding of the heat transferred from the gas into the tank wall (carbon fiber reinforced plastic (CFRP) material) during hydrogen fueling is necessary. Its thermal properties are needed in estimating heat loss accurately during hydrogen fueling. The CFRP has anisotropic thermal properties, because it consists of an adhesive agent and layers of the CFRP which is wound with a carbon fiber. In this paper, the thermal diffusivity and thermal conductivity of the tank wall material were measured by an inverse solution for one-dimensional unsteady heat conduction. As a result, the thermal diffusivity and thermal conductivity were 2.09 × 10^{-6}{ m}2{\\cdot }{s}^{-1} and 3.06{ W}{\\cdot }{m}{\\cdot }^{-1}{K}^{-1} for the axial direction, while they were 6.03 × 10^{-7} {m}2{\\cdot }{s}^{-1} and 0.93 {W}{\\cdot }{m}^{-1}{\\cdot }{K}^{-1} for the radial direction. The thermal conductivity for the axial direction was about three times higher than that for the radial direction. The thermal diffusivity shows the same trend in both directions because the thermal capacity, ρ c, is independent of direction, where ρ is the density and c is the heat capacity.

  13. Investigation on the magneto-optical Voigt effects in surface plasmon modes and anisotropic photonic band gap in the three-dimensional magnetized plasma photonic crystals as the mixed polarized modes considered

    NASA Astrophysics Data System (ADS)

    Zhang, Hai-Feng; Liu, Shao-Bin; Ding, Guo-Wen

    2014-10-01

    In this paper, the magneto-optical Voigt effects in surface plasmon modes and anisotropic photonic band gaps (PBGs) of the three-dimensional (3D) magnetized plasma photonic crystals (MPPCs) with face-centered-cubic lattices are theoretically investigated based on the modified plane wave expansion (PWE) method, which are the homogeneous Te (tellurium) spheres immersed in the homogeneous magnetized plasma background, as the mixed polarized modes are considered. The more general condition is considered, and the anisotropic PBGs are not only for the extraordinary and ordinary modes but also for mixed polarized modes. The equations for computing such anisotropic PBGs are theoretically deduced. Theoretical simulations show that the anisotropic PBGs and a flatbands region can be observed in the dispersive curve. Compared to the similar 3D MPPCs containing the isotropic dielectric or uniaxial material spheres, the larger PBGs can be obtained as the extraordinary axis of the inserted uniaxial material is along the Г-H symmetry line although the region of flatbands is also different. However, the relative bandwidths of PBGs for such two cases are almost the same. The interesting properties of surface plasmon modes can also be found, which are that the upper edge of flatbands region cannot be tuned by the filling factor but can almost linearly increase on increasing the plasma frequency and plasma cyclotron frequency (the external magnetic field), respectively. The effects of the filling factor, plasma frequency and plasma cyclotron frequency on the anisotropic PBGs are investigated in detail, respectively. Theoretical calculations also show that such PBGs can be manipulated by the parameters as mentioned above.

  14. Plasma aldosterone and sweat sodium concentrations after exercise and heat acclimation

    NASA Technical Reports Server (NTRS)

    Kirby, C. R.; Convertino, V. A.

    1986-01-01

    The relationship between plasma aldosterone levels and sweat sodium excretion after chronic exercise and heat acclimation was investigated, using subjects exercised, at 40 C and 45 percent humidity, for 2 h/day on ten consecutive days at 45 percent of their maximal oxygen uptake. The data indicate that, following heat acclimation, plasma aldosterone concentrations decrease, and that the eccrine gland responsiveness to aldosterone, as represented by sweat sodium reabsorption, may be augmented through exercise and heat acclimation.

  15. LHCD and ICRF heating experiments in H-mode plasmas on EAST

    SciTech Connect

    Zhang, X. J.; Zhao, Y. P.; Wan, B. N.; Ding, B. J.; Xu, G. S.; Gong, X. Z.; Li, J. G.; Lin, Y.; Wukitch, S.; Taylor, G.; Noterdaeme, J. M.; Braun, F.; Magne, R.; Litaudon, X.; Kumazawa, R.; Kasahara, H.; Collaboration: EAST Team

    2014-02-12

    An ICRF system with power up to 6.0 MW and a LHCD system up to 4MW have been applied for heating and current drive experiments on EAST. Intensive lithium wall coating was intensively used to reduce particle recycling and Hydrogen concentration in Deuterium plasma, which is needed for effective ICRF and LHCD power absorption in high density plasmas. Significant progress has been made with ICRF heating and LHW current drive for realizing the H-mode plasma operation in EAST. In 2010, H-mode was generated and sustained by LHCD alone, where lithium coating and gas puffing launcher mouth were applied to improve the LHCD power coupling and penetration into the core plasmas at high density of H-modes. During the last two experimental campaigns, ICRF Heating experiments were carried out at the fixed frequency of 27MHz, achieving effective ions and electrons heating with the H Minority Heating (H-MH) mode, where electrons are predominantly heated by collisions with high energy minority ions. The H-MH mode gave the best plasma performance, and realized H-mode alone in 2012. Combination of ICRF and LHW power injection generated the H-mode plasmas with various ELMy characteristics. The first successful application of the ICRF Heating in the D (He3) plasma was also achieved. The progress on ICRF heating, LHCD experiments and their application in achieving H-mode operation from last two years will be discussed in this report.

  16. Heating of ions by low-frequency Alfven waves in partially ionized plasmas

    SciTech Connect

    Dong Chuanfei; Paty, Carol S.

    2011-03-15

    In the solar atmosphere, the chromospheric and coronal plasmas are much hotter than the visible photosphere. The heating of the solar atmosphere, including the partially ionized chromosphere and corona, remains largely unknown. In this letter, we demonstrate that the ions can be substantially heated by Alfven waves with very low frequencies in partially ionized low-beta plasmas. This differs from other Alfven wave related heating mechanisms such as ion-neutral collisional damping of Alfven waves and heating described by previous work on resonant Alfven wave heating. We find that the nonresonant Alfven wave heating is less efficient in partially ionized plasmas than when there are no ion-neutral collisions, and the heating efficiency depends on the ratio of the ion-neutral collision frequency to the ion gyrofrequency.

  17. Spark-plasma-sintering magnetic field assisted compaction of Co{sub 80}Ni{sub 20} nanowires for anisotropic ferromagnetic bulk materials

    SciTech Connect

    Ouar, Nassima; Schoenstein, Frédéric; Mercone, Silvana; Farhat, Samir; Jouini, Noureddine; Villeroy, Benjamin; Leridon, Brigitte

    2013-10-28

    We developed a two-step process showing the way for sintering anisotropic nanostructured bulk ferromagnetic materials. A new reactor has been optimized allowing the synthesis of several grams per batch of nanopowders via a polyol soft chemistry route. The feasibility of the scale-up has been successfully demonstrated for Co{sub 80}Ni{sub 20} nanowires and a massic yield of ∼97% was obtained. The thus obtained nanowires show an average diameter of ∼6 nm and a length of ∼270 nm. A new bottom-up strategy allowed us to compact the powder into a bulk nanostructured system. We used a spark-plasma-sintering technique under uniaxial compression and low temperature assisted by a permanent magnetic field of 1 T. A macroscopic pellet of partially aligned nanowire arrays has been easily obtained. This showed optimized coercive properties along the direction of the magnetic field applied during compaction (i.e., the nanowires' direction)

  18. Transport in JET H-mode Plasmas with Beam and Ion Cyclotron Heating

    SciTech Connect

    R.V. Budny, et. al.

    2012-07-13

    Ion Cyclotron (IC) Range of Frequency waves and neutral beam (NB) injection are planned for heating in ITER and other future tokamaks. It is important to understand transport in plasmas with NB and IC to plan, predict, and improve transport and confinement. Transport predictions require simulations of the heating profiles, and for this, accurate modeling of the IC and NB heating is needed.

  19. Plasma heating at collisionless shocks due to the kinetic cross-field streaming instability

    NASA Technical Reports Server (NTRS)

    Winske, D.; Quest, K. B.; Tanaka, M.; Wu, C. S.

    1985-01-01

    Heating at collisionless shocks due to the kinetic cross-field streaming instability, which is the finite beta (ratio of plasma to magnetic pressure) extension of the modified two stream instability, is studied. Heating rates are derived from quasi-linear theory and compared with results from particle simulations to show that electron heating relative to ion heating and heating parallel to the magnetic field relative to perpendicular heating for both the electrons and ions increase with beta. The simulations suggest that electron dynamics determine the saturation level of the instability, which is manifested by the formation of a flattop electron distribution parallel to the magnetic field. As a result, both the saturation levels of the fluctuations and the heating rates decrease sharply with beta. Applications of these results to plasma heating in simulations of shocks and the earth's bow shock are described.

  20. Heating dynamics and extreme ultraviolet radiation emission of laser-produced Sn plasmas

    SciTech Connect

    Yuspeh, S.; Sequoia, K. L.; Tao, Y.; Tillack, M. S.; Burdt, R. A.; Najmabadi, F.

    2010-06-28

    The impact of 1.064 mum laser absorption depth on the heating and in-band (2% bandwidth) 13.5 nm extreme ultraviolet emissions in Sn plasmas is investigated experimentally and numerically. In-band emission lasting longer than the laser pulse and separation between the laser absorption and in-band emission region are observed. Maximum efficiency is achieved by additional heating of the core of the plasma to allow the optimal temperature to expand to a lower and more optically thin density. This leads to higher temperature plasma that emits less in-band light as compared to CO{sub 2} produced plasma sources for the same application.

  1. Observation of a high-confinement regime in a tokamak plasma with ion cyclotron resonance heating

    NASA Astrophysics Data System (ADS)

    Steinmetz, K.; Noterdaeme, J.-M.; Wagner, F.; Wesner, F.; Bäumler, J.; Becker, G.; Bosch, H. S.; Brambilla, M.; Braun, F.; Brocken, H.; Eberhagen, A.; Fritsch, R.; Fussmann, G.; Gehre, O.; Gernhardt, J.; v. Gierke, G.; Glock, E.; Gruber, O.; Haas, G.; Hofmann, J.; Hofmeister, F.; Izvozchikov, A.; Janeschitz, G.; Karger, F.; Keilhacker, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lisitano, G.; van Mark, E.; Mast, F.; Mayer, H. M.; McCormick, K.; Meisel, D.; Mertens, V.; Müller, E. R.; Murmann, H.; Niedermeyer, H.; Poschenrieder, W.; Puri, S.; Rapp, H.; Röhr, H.; Ryter, F.; Schmitter, K.-H.; Schneider, F.; Setzensack, C.; Siller, G.; Smeulders, P.; Söldner, F.; Speth, E.; Steuer, K.-H.; Vollmer, O.; Wedler, H.; Zasche, D.

    1987-01-01

    The H mode in ion cyclotron-resonance-heated plasmas has been investigated with and without additional neutral beam injection. Ion cyclotron-resonance heating can cause the transition into a high-confinement regime (H mode) in combination with beam heating. The H mode, however, has also been realized-for the first time-with ion cyclotron-resonance heating alone in the D (H)-hydrogen minority scheme at an absorbed rf power of 1.1 MW.

  2. Finite-difference schemes for anisotropic diffusion

    SciTech Connect

    Es, Bram van; Koren, Barry; Blank, Hugo J. de

    2014-09-01

    In fusion plasmas diffusion tensors are extremely anisotropic due to the high temperature and large magnetic field strength. This causes diffusion, heat conduction, and viscous momentum loss, to effectively be aligned with the magnetic field lines. This alignment leads to different values for the respective diffusive coefficients in the magnetic field direction and in the perpendicular direction, to the extent that heat diffusion coefficients can be up to 10{sup 12} times larger in the parallel direction than in the perpendicular direction. This anisotropy puts stringent requirements on the numerical methods used to approximate the MHD-equations since any misalignment of the grid may cause the perpendicular diffusion to be polluted by the numerical error in approximating the parallel diffusion. Currently the common approach is to apply magnetic field-aligned coordinates, an approach that automatically takes care of the directionality of the diffusive coefficients. This approach runs into problems at x-points and at points where there is magnetic re-connection, since this causes local non-alignment. It is therefore useful to consider numerical schemes that are tolerant to the misalignment of the grid with the magnetic field lines, both to improve existing methods and to help open the possibility of applying regular non-aligned grids. To investigate this, in this paper several discretization schemes are developed and applied to the anisotropic heat diffusion equation on a non-aligned grid.

  3. The Development of RF Heating of Magnetically Confined Deuterium-Tritium Plasmas

    SciTech Connect

    B.P. LeBlanc; C.K. Phillips; J.C. Hosea; R. Majeski; S. Bernabei

    1999-06-01

    The experimental and theoretical development of ion cyclotron radiofrequency heating (ICRF) in toroidal magnetically-confined plasmas recently culminated with the demonstration of ICRF heating of D-T plasmas, first in the Tokamak Fusion Test Reactor (TFTR) and then in the Joint European Torus (JET). Various heating schemes based on the cyclotron resonances between the plasma ions and the applied ICRF waves have been used, including second harmonic tritium, minority deuterium, minority helium-3, mode conversion at the D-T ion-ion hybrid layer, and ion Bernstein wave heating. Second harmonic tritium heating was first shown to be effective in a reactor-grade plasma in TFTR. D-minority heating on JET has led to the achievement of Q = 0.22, the ratio of fusion power produced to RF power input, sustained over a few energy confinement times. In this paper, some of the key building blocks in the development of rf heating of plasmas are reviewed and prospects for the development of advanced methods of plasma control based on the application of rf waves are discussed.

  4. The development of RF heating of magnetically confined deuterium-tritium plasmas

    SciTech Connect

    Hosea, J. C.; Bemabei, S.; LeBlanc, B. P.; Majeski, R.; Phillips, C. K.; Schilling, G.; Wilson the TFTR Team, J. R.

    1999-09-20

    The experimental and theoretical development of ion cyclotron radiofrequency heating (ICRF) in toroidal magnetically-confined plasmas recently culminated with the demonstration of ICRF heating of D-T plasmas, first in the Tokamak Fusion Test Reactor (TFTR) and then in the Joint European Torus (JET). Various heating schemes based on the cyclotron resonances between the plasma ions and the applied ICRF waves have been used, including second harmonic tritium, minority deuterium, minority helium-3, mode conversion at the D-T ion-ion hybrid layer, and ion Bernstein wave heating. Second harmonic tritium heating was first shown to be effective in a reactor-grade plasma in TFTR. D-minority heating on JET has led to the achievement of Q=0.22, the ratio of fusion power produced to RF power input, sustained over a few energy confinement times. In this paper, some of the key building blocks in the development of rf heating of plasmas are reviewed and prospects for the development of advanced methods of plasma control based on the application of rf waves are discussed. (c) 1999 American Institute of Physics.

  5. Plasma self-heating and saturation due to numerical instabilities

    SciTech Connect

    Birdsall, C.K.; Maron, N.

    1980-06-01

    The cold-beam nonphysical instability due to the aliases produced by the numerical spatial grid is presented in detail for momentum-conserving linear weighting codes. Additions to previous work include: linear analysis dispersion diagrams showing large growth rates, ..omega../sub i/< or =0.2 ..omega../sub p/; methods for reducing ..omega../sub i/, effectively broadening the finite-size particle width; simulation results verifying the linear theory, plus plots showing the p=1 alias in phase space (..nu../sub x/, x); the growth of beam, thermal spread (..nu../sub t//sup 2/ in temperature) an loss of energy conservation; end-of-growth (saturation at small thermal spread (lambda/sub D//..delta..x=upsilon/sub t//..omega../sub p/..delta..xapprox. =0.046, for lambda/sub B//..delta..xequivalent upsilon/sub 0//..omega../sub p/..delta..x> or =0.3, i.e., upsilon/sub t/< or =0.14upsilon/sub 0/), with return to near energy conservation (stability); demonstration of no growth for a warm beam, with upsilon/sub t/(initial)> or =upsilon/sub t/(saturation); and the mechanism of stabilization (trapping). A thermal (Maxwellian) plasma, also nonphysically unstable at small lambda/sub D//..delta..x, is also found to approach stabilization by self-heating. The two-stream physical instability is affected by the grid, with the aliasing instability also present; the linear theory for this is presented, with guidelines for minimizing the effects of the grid.

  6. Electron heating in radio-frequency capacitively coupled atmospheric-pressure plasmas

    SciTech Connect

    Liu, D. W.; Iza, F.; Kong, M. G.

    2008-12-29

    In atmospheric-pressure plasmas the main electron heating mechanism is Ohmic heating, which has distinct spatial and temporal evolutions in the {alpha} and {gamma} modes. In {gamma} discharges, ionizing avalanches in the sheaths are initiated not only by secondary electrons but also by metastable pooling reactions. In {alpha} discharges, heating takes place at the sheath edges and in contrast with low-pressure plasmas, close to 50% of the power absorbed by the electrons is absorbed at the edge of the retreating sheaths. This heating is due to a field enhancement caused by the large collisionality in atmospheric-pressure discharges.

  7. Multiple ionization of metal ions by ECR heating of electrons in vacuum arc plasmas

    NASA Astrophysics Data System (ADS)

    Vodopyanov, A. V.; Golubev, S. V.; Zorin, V. G.; Razin, S. V.; Vizir, A. V.; Nikolaev, A. G.; Oks, E. M.; Yushkov, G. Yu.

    2004-05-01

    A joint research and development effort has been initiated, whose ultimate goal is the enhancement of the mean ion charge states in vacuum arc metal plasmas by a combination of a vacuum arc discharge and electron cyclotron resonance (ECR) heating. Metal plasma was generated by a special vacuum arc mini-gun. Plasma was pumped by high frequency gyrotron-generated microwave radiation. The results have demonstrated substantial multiple ionization of metal ions. For a lead plasma, ECR heating increased the maximum attainable ion charge state from Pb2+ up to Pb6+. The confinement parameter was as high as ˜109 cm-3 s. Further increase of the ion charge states will be attained by increasing the vacuum arc plasma density and optimizing the ECR heating conditions.

  8. Thin Current Sheets and Associated Electron Heating in Turbulent Space Plasma

    NASA Astrophysics Data System (ADS)

    Chasapis, A.; Retinò, A.; Sahraoui, F.; Vaivads, A.; Khotyaintsev, Yu. V.; Sundkvist, D.; Greco, A.; Sorriso-Valvo, L.; Canu, P.

    2015-05-01

    Intermittent structures, such as thin current sheets, are abundant in turbulent plasmas. Numerical simulations indicate that such current sheets are important sites of energy dissipation and particle heating occurring at kinetic scales. However, direct evidence of dissipation and associated heating within current sheets is scarce. Here, we show a new statistical study of local electron heating within proton-scale current sheets by using high-resolution spacecraft data. Current sheets are detected using the Partial Variance of Increments (PVI) method which identifies regions of strong intermittency. We find that strong electron heating occurs in high PVI (>3) current sheets while no significant heating occurs in low PVI cases (<3), indicating that the former are dominant for energy dissipation. Current sheets corresponding to very high PVI (>5) show the strongest heating and most of the time are consistent with ongoing magnetic reconnection. This suggests that reconnection is important for electron heating and dissipation at kinetic scales in turbulent plasmas.

  9. US-Japan workshop Q-181 on high heat flux components and plasma-surface interactions for next devices: Proceedings

    SciTech Connect

    McGrath, R.T.; Yamashina, T.

    1994-04-01

    This report contain viewgraphs of papers from the following sessions: plasma facing components issues for future machines; recent PMI results from several tokamaks; high heat flux technology; plasma facing components design and applications; plasma facing component materials and irradiation damage; boundary layer plasma; plasma disruptions; conditioning and tritium; and erosion/redeposition.

  10. MAGNETIC END CLOSURES FOR PLASMA CONFINING AND HEATING DEVICES

    DOEpatents

    Post, R.F.

    1963-08-20

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

  11. Improving the efficiency of plasma heat treatment of metals

    NASA Astrophysics Data System (ADS)

    Gabdrakhmanov, Az T.; Israphilov, I. H.; Galiakbarov, A. T.; Samigullin, A. D.; Gabdrakhmanov, Al T.

    2016-01-01

    This paper proposes an effective way of the plasma hardening the surface layer at the expense combined influence of the plasma jet and a cold air flow. After that influence occurs a distinctive by plasma treatment microstructure with increased microhardness (an increase of 35%) and depth. There is proposed an improved design of the vortex tube for receiving the air flow with a temperature of 20 C to - 120C.

  12. Self-Regulated Plasma Heat Flux Mitigation Due to Liquid Sn Vapor Shielding.

    PubMed

    van Eden, G G; Morgan, T W; Aussems, D U B; van den Berg, M A; Bystrov, K; van de Sanden, M C M

    2016-04-01

    A steady-state high-flux H or He plasma beam was balanced against the pressure of a Sn vapor cloud for the first time, resulting in a self-regulated heat flux intensity near the liquid surface. A temperature response of the liquid surface characterized by a decoupling from the received heating power and significant cooling of the plasma in the neutral Sn cloud were observed. The plasma heat flux impinging on the target was found to be mitigated, as heat was partially dissipated by volumetric processes in the vapor cloud rather than wholly by surface effects. These results motivate further exploration of liquid metal solutions to the critical challenge of heat and particle flux handling in fusion power plants. PMID:27081983

  13. Self-Regulated Plasma Heat Flux Mitigation Due to Liquid Sn Vapor Shielding

    NASA Astrophysics Data System (ADS)

    van Eden, G. G.; Morgan, T. W.; Aussems, D. U. B.; van den Berg, M. A.; Bystrov, K.; van de Sanden, M. C. M.

    2016-04-01

    A steady-state high-flux H or He plasma beam was balanced against the pressure of a Sn vapor cloud for the first time, resulting in a self-regulated heat flux intensity near the liquid surface. A temperature response of the liquid surface characterized by a decoupling from the received heating power and significant cooling of the plasma in the neutral Sn cloud were observed. The plasma heat flux impinging on the target was found to be mitigated, as heat was partially dissipated by volumetric processes in the vapor cloud rather than wholly by surface effects. These results motivate further exploration of liquid metal solutions to the critical challenge of heat and particle flux handling in fusion power plants.

  14. Density and temperature scaling of disorder-induced heating in ultracold plasmas

    SciTech Connect

    Bergeson, S. D.; Denning, A.; Lyon, M.; Robicheaux, F.

    2011-02-15

    We report measurements and simulations of disorder-induced heating in ultracold neutral plasmas. Fluorescence from plasma ions is excited using a detuned probe laser beam while the plasma relaxes from its initially disordered nonequilibrium state. This method probes the wings of the ion velocity distribution. The simulations yield information on time-evolving plasma parameters that are difficult to measure directly and make it possible to connect the fluorescence signal to the rms velocity distribution. The disorder-induced heating signal can be used to estimate the electron and ion temperatures {approx}100 ns after the plasma is created. This is particularly interesting for plasmas in which the electron and ion temperatures are not known.

  15. Plasma diagnostics approach to welding heat source/molten pool interaction

    SciTech Connect

    Key, J.F.; McIlwain, M.E.; Isaacson, L.

    1980-01-01

    Plasma diagnostic techniques show that weld fusion zone profile and loss of metal vapors from the molten pool are strongly dependent on both the intensity and distribution of the heat source. These plasma properties, are functions of cathode vertex angle and thermal conductivity of the shielding gas, especially near the anode.

  16. Numerical Investigation of Radiative Heat Transfer in Laser Induced Air Plasmas

    NASA Technical Reports Server (NTRS)

    Liu, J.; Chen, Y. S.; Wang, T. S.; Turner, James E. (Technical Monitor)

    2001-01-01

    Radiative heat transfer is one of the most important phenomena in the laser induced plasmas. This study is intended to develop accurate and efficient methods for predicting laser radiation absorption and plasma radiative heat transfer, and investigate the plasma radiation effects in laser propelled vehicles. To model laser radiation absorption, a ray tracing method along with the Beer's law is adopted. To solve the radiative transfer equation in the air plasmas, the discrete transfer method (DTM) is selected and explained. The air plasma radiative properties are predicted by the LORAN code. To validate the present nonequilibrium radiation model, several benchmark problems are examined and the present results are found to match the available solutions. To investigate the effects of plasma radiation in laser propelled vehicles, the present radiation code is coupled into a plasma aerodynamics code and a selected problem is considered. Comparisons of results at different cases show that plasma radiation plays a role of cooling plasma and it lowers the plasma temperature by about 10%. This change in temperature also results in a reduction of the coupling coefficient by about 10-20%. The present study indicates that plasma radiation modeling is very important for accurate modeling of aerodynamics in a laser propelled vehicle.

  17. Electron heating via self-excited plasma series resonance in geometrically symmetric multi-frequency capacitive plasmas

    NASA Astrophysics Data System (ADS)

    Schüngel, E.; Brandt, S.; Donkó, Z.; Korolov, I.; Derzsi, A.; Schulze, J.

    2015-08-01

    The self-excitation of plasma series resonance (PSR) oscillations plays an important role in the electron heating dynamics in capacitively coupled radio-frequency (CCRF) plasmas. In a combined approach of PIC/MCC simulations and a theoretical model based on an equivalent circuit, we investigate the self-excitation of PSR oscillations and their effect on the electron heating in geometrically symmetric CCRF plasmas driven by multiple consecutive harmonics. The discharge symmetry is controlled via the electrical asymmetry effect (EAE), i.e. by varying the total number of harmonics and tuning the phase shifts between them. It is demonstrated that PSR oscillations will be self-excited under both symmetric and asymmetric conditions, if (i) the charge-voltage relation of the plasma sheaths deviates from a simple quadratic behavior and (ii) the inductance of the plasma bulk exhibits a temporal modulation. These two effects have been neglected up to now, but we show that they must be included in the model in order to properly describe the nonlinear series resonance circuit and reproduce the self-excitation of PSR oscillations, which are observed in the electron current density resulting from simulations of geometrically symmetric CCRF plasmas. Furthermore, the effect of PSR self-excitation on the discharge current and the plasma properties, such as the potential profile, is illustrated by applying Fourier analysis. High-frequency oscillations in the entire spectrum between the applied frequencies and the local electron plasma frequency are observed. As a consequence, the electron heating is strongly enhanced by the presence of PSR oscillations. A complex electron heating dynamics is found during the expansion phase of the sheath, which is fully collapsed, when the PSR is initially self-excited. The nonlinear electron resonance heating (NERH) associated with the PSR oscillations causes a spatial asymmetry in the electron heating. By discussing the resulting ionization

  18. Coupled interactions between tungsten surfaces and transient high-heat-flux deuterium plasmas

    NASA Astrophysics Data System (ADS)

    Takamura, S.; Uesugi, Y.

    2015-03-01

    Fundamental studies on the interactions between transient deuterium-plasma heat pulses and tungsten surfaces were carried out in terms of electrical, mechanical and thermal response in a compact plasma device AIT-PID (Aichi Institute of Technology-Plasma Irradiation Device). Firstly, electron-emission-induced surface-temperature increase is discussed in the surface-temperature range near tungsten's melting point, which is accomplished by controlling the sheath voltage and power transmission factor. Secondly, anomalous penetration of tungsten atomic efflux into the surrounding plasma was observed in addition to a normal layered population; it is discussed in terms of the effect of substantial tungsten influx into the deuterium plasma, which causes dissipation of plasma electron energy. Thirdly, a momentum input from pulsed plasma onto a tungsten target was observed visually. The force is estimated numerically by the accelerated ion flow to the target as well as the reaction of tungsten-vapour efflux. Finally, a discussion follows on the effects of the plasma heat pulses on the morphology of tungsten surface (originally a helium-induced ‘fuzzy’ nanostructure). A kind of bifurcated effect is obtained: melting and annealing. Open questions remain for all the phenomena observed, although sheath-voltage-dependent plasma-heat input may be a key parameter. Discussions on all these phenomena are provided by considering their implications to tokamak fusion devices.

  19. Stochastic Ion Heating from Many Overlapping Laser Beams in Fusion Plasmas

    NASA Astrophysics Data System (ADS)

    Michel, P.; Rozmus, W.; Williams, E. A.; Divol, L.; Berger, R. L.; Town, R. P. J.; Glenzer, S. H.; Callahan, D. A.

    2012-11-01

    In this Letter, we show through numerical simulations and analytical results that overlapping multiple (N) laser beams in plasmas can lead to strong stochastic ion heating from many (∝N2) electrostatic perturbations driven by beat waves between pairs of laser beams. For conditions typical of inertial-confinement-fusion experiment conditions, hundreds of such beat waves are driven in mm3-scale plasmas, leading to ion heating rates of several keV/ns. This mechanism saturates cross-beam energy transfer, with a reduction of linear gains by a factor ˜4-5 and can strongly modify the overall hydrodynamics evolution of such laser-plasma systems.

  20. Spatiotemporal evolution of ponderomotive electron heating in axially inhomogeneous collisionless plasma

    SciTech Connect

    Mishra, S. K.; Sharma, A.

    2013-07-15

    We investigate the spatiotemporal focusing dynamics of a Gaussian laser pulse in preformed collisionless plasma subjected to an axial nonuniformity in the plasma density. In order to follow up the pulse dynamics, a nonlinear Schrödinger wave equation characterizing the beam spot size in space and time frame has been derived and solved numerically to investigate the propagation characteristics as the pulse advances in the plasma. The effect of inhomogeneity on focusing length and ponderomotive electron heating have been analyzed and illustrated graphically. It is seen that ponderomotive heating is quite sensitive to the inhomogeneity parameters and the energy gain by electrons can be optimized by suitable choice of parameters.

  1. Stochastic ion heating from many overlapping laser beams in fusion plasmas.

    PubMed

    Michel, P; Rozmus, W; Williams, E A; Divol, L; Berger, R L; Town, R P J; Glenzer, S H; Callahan, D A

    2012-11-01

    In this Letter, we show through numerical simulations and analytical results that overlapping multiple (N) laser beams in plasmas can lead to strong stochastic ion heating from many (~N(2)) electrostatic perturbations driven by beat waves between pairs of laser beams. For conditions typical of inertial-confinement-fusion experiment conditions, hundreds of such beat waves are driven in mm(3)-scale plasmas, leading to ion heating rates of several keV/ns. This mechanism saturates cross-beam energy transfer, with a reduction of linear gains by a factor ~4-5 and can strongly modify the overall hydrodynamics evolution of such laser-plasma systems. PMID:23215392

  2. Generalized parallel heat transport equations in collisional to weakly collisional plasmas

    NASA Astrophysics Data System (ADS)

    Zawaideh, Emad; Kim, N. S.; Najmabadi, Farrokh

    1988-11-01

    A new set of two-fluid heat-transport equations for heat conduction in collisional to weakly collisional plasmas was derived on the basis of gyrokinetic equations in flux coordinates. In these equations, no restrictions on the anisotropy of the ion distribution function or the collisionality are imposed. In the highly collisional limit, these equations reduce to the classical heat conduction equation of Spitzer and Haerm (1953), while in the weakly collisional limit, they describe a saturated heat flux. Numerical examples comparing these equations with conventional heat transport equations are presented.

  3. Temperature Diffusion Waves in Magnetized Plasmas

    NASA Astrophysics Data System (ADS)

    Reynolds, M. A.; Morales, G. J.; Maggs, J. E.

    2002-11-01

    Fluctuations of localized heat sources manifest themselves as temperature diffusion waves throughout the plasma surrounding the source, with anisotropic propagation characteristics due to the anisotropic nature of the thermal conductivity. In fact, fluctuations in electron temperature have been observed experimentally in studies of heat transport in magnetized temperature filaments (Burke et al., Phys. Plasmas, 7, 1397, 2000) where the anisotropic nature was of paramount interest. Here, the theory of temperature diffusion waves in a magnetized plasma is presented, and the properties of these waves are investigated both analytically and numerically. Results from the one-dimensional (parallel), linear theory of diffusion waves are used to shed light on the results obtained by a two-dimensional (parallel and perpendicular) transport code. Features that are investigated include the spatial structure of wave amplitude and phase, the effect that the size of the source region has on the spatial structure (i.e., radial localization), and the strongly nonlinear (large amplitude source fluctuations) limit.

  4. Numerical simulation of heat fluxes in a two-temperature plasma at shock tube walls

    NASA Astrophysics Data System (ADS)

    Kuznetsov, E. A.; Poniaev, S. A.

    2015-12-01

    Numerical simulation of a two-temperature three-component Xenon plasma flow is presented. A solver based on the OpenFOAM CFD software package is developed. The heat flux at the shock tube end wall is calculated and compared with experimental data. It is shown that the heat flux due to electrons can be as high as 14% of the total heat flux.

  5. Mass Spectrometry of 3D-printed plastic parts under plasma and radiative heat environments

    NASA Astrophysics Data System (ADS)

    Rivera, W. F.; Romero-Talamas, C. A.; Bates, E. M.; Birmingham, W.; Takeno, J.; Knop, S.

    2015-11-01

    We present the design and preliminary results of a mass spectrometry system used to assess vacuum compatibility of 3D-printed parts, developed at the Dusty Plasma Laboratory of the University of Maryland Baltimore County (UMBC). A decrease in outgassing was observed when electroplated parts were inserted in the test chamber vs. non electroplated ones. Outgassing will also be tested under different environments such as plasma and radiative heat. Heat will be generated by a titanium getter pump placed inside a 90 degree elbow, such that titanium does not coat the part. A mirror inside the elbow will be used to throttle the heat arriving at the part. Plasma exposure of 3D printed parts will be achieved by placing the parts in a separate chamber connected to the spectrometer by a vacuum line that is differentially pumped. The signals from the mass spectrometer will be analyzed to see how the vacuum conditions fluctuate under different plasma discharges.

  6. Effect of axial finiteness on electron heating in low-frequency inductively coupled plasmas

    SciTech Connect

    Aman-ur-Rehman; Pu, Y.-K.

    2006-10-15

    Total power absorption inside the plasma (by taking the thermal motion of the electrons into account) has been calculated using different inductively coupled plasma models. The comparison shows that in the low-frequency region the results of the semi-infinite plasma models are different from those of the finite-length plasma models. The semi-infinite plasma models show net reduction of heating in the low-frequency region, due to thermal motion of the electrons from inside the skin region to outside the skin region. The finite-length plasma models on the other hand (due to change in the skin depth owing to the boundary condition of E=0 at z=L, and reflection of electrons from the plasma boundary) show that the decrease in heating due to the motion of the electrons from inside the skin depth to outside the skin depth is recovered by the reflection of the electrons from the plasma boundary. Hence, it is concluded that the results of the semi-infinite plasma models presented by Tyshetskiy et al. [Phys Rev. Lett. 90, 255002 (2003)] can be misleading (in the low-frequency region), since they overlooked the effect of axial finiteness of the plasma.

  7. The behavior of neutron emissions during ICRF minority heating of plasma at EAST

    NASA Astrophysics Data System (ADS)

    Zhong, Guoqiang; Cao, Hongrui; Hu, Liqun; Zhou, Ruijie; Xiao, Min; Li, Kai; Pu, Neng; Huang, Juan; Liu, Guangzhu; Lin, Shiyao; Lyu, Bo; Liu, Haiqing; Zhang, Xinjun; EAST Team

    2016-07-01

    Ion cyclotron radio frequency (ICRF) wave heating is a primary method to heat ions in the Experimental Advanced Superconducting Tokamak (EAST). Through neutron diagnostics, effective ion heating was observed in hydrogenminority heating (MH) scenarios. At present, investigation of deuterium–deuterium (DD) fusion neutrons is mostly based on time-resolved flux monitor and spectrometer measurements. When the ICRF was applied, the neutron intensity became one order higher. The H/H  +  D ratio was in the range of 5–10%, corresponding to the hydrogen MH dominated scenario, and a strong high energy tail was not displayed on the neutron spectrum that was measured by a liquid scintillator. Moreover, ion temperature in the plasma center (T i) was inversely calculated by the use of neutron source strength (S n) and the plasma density based on classical fusion reaction equations. This result indicates that T i increases by approximately 30% in L-mode plasma, and by more than 50% in H-mode plasma during ICRF heating, which shows good agreement with x-ray crystal spectrometer (XCS) diagnostics. Finally, the DD neutron source strength scaling law, with regard to plasma current (I P) and ICRF coupling power (P RF) on the typical minority heating condition, was obtained by statistical analysis.

  8. Strong RF Heating in a Mirror During Plasma Build-up

    SciTech Connect

    Moiseenko, V. E.; Dreval, N. B.; Aagren, O.; Stepanov, K. N.; Tereshin, V. I.; Burdakov, A. V.; Kalinin, P. V.

    2007-09-28

    A heating method of partially onized plasma has been described in Ref. [1]. It exploits the collisional damping of the fast waves that is high owing to charge exchange collisions. Since the time of heating is limited by the duration of neutral gas ionization, the heating needs to be strong enough to achieve a high final ion temperature. This heating method has been studied numerically in the framework of the MHD approximaton in inhomogeneous cylindrical plasma. The influences of the ratio of the mean free path of the neutral atoms to the plasma radius, the initial ions concentration, the characteristics of the interaction of the neutral atoms with the chamber wall and of other parameters on the plasma heating dynamics are examined. A scenario of RF plasma heating in one of the central cells of the multi-mirror device GOL-3 at Novosibirsk in Russia is theoretically developed, in which the final ion temperature exceeds the ion oscilation energy in the RF field by one order of magnitude.

  9. Fast wave heating and current drive in tokamak plasmas with negative central shear

    SciTech Connect

    Forest, C.B.; Petty, C.C.; Baity, F.W.

    1996-07-01

    Fast waves provide an excellent tool for heating electrons and driving current in the central region of tokamak plasmas. In this paper, we report the use of centrally peaked electron heating and current drive to study transport in plasmas with negative central shear (NCS). Tokamak plasmas with NCS offer the potential of reduced energy transport and improved MHD stability properties, but will require non-inductive current drive to maintain the required current profiles. Fast waves, combined with neutral beam injection, provide the capability to change the central current density evolution and independently vary {ital T{sub e}}, and {ital T{sub i}} for transport studies in these plasmas. Electron heating also reduces the collisional heat exchange between electrons and ions and reduces the power deposition from neutral beams into electrons, thus improving the certainty in the estimate of the electron heating. The first part of this paper analyzes electron and ion heat transport in the L-mode phase of NCS plasmas as the current profile resistively evolves. The second part of the paper discusses the changes that occur in electron as well as ion energy transport in this phase of improved core confinement associated with NCS.

  10. High heat flux properties of pure tungsten and plasma sprayed tungsten coatings

    NASA Astrophysics Data System (ADS)

    Liu, X.; Tamura, S.; Tokunaga, K.; Yoshida, N.; Noda, N.; Yang, L.; Xu, Z.

    2004-08-01

    High heat flux properties of pure tungsten and plasma sprayed tungsten coatings on carbon substrates have been studied by annealing and cyclic heat loading. The recrystallization temperature and an activation energy QR=126 kJ/mol for grain growth of tungsten coating by vacuum plasma spray (VPS) were estimated, and the microstructural changes of multi-layer tungsten and rhenium interface pre-deposited by physical vapor deposition (PVD) with anneal temperature were investigated. Cyclic load tests indicated that pure tungsten and VPS-tungsten coating could withstand 1000 cycles at 33-35 MW/m 2 heat flux and 3 s pulse duration, and inert gas plasma spray (IPS)-tungsten coating showed local cracks by 300 cycles but did not induce failure by further cycles. However, the failure of pure tungsten and VPS-tungsten coating by fatigue cracking was observed under higher heat load (55-60 MW/m 2) for 420 and 230 cycles, respectively.

  11. "Hot" Non-flaring Plasmas in Active Region Cores Heated by Single Nanoflares

    NASA Astrophysics Data System (ADS)

    Barnes, Will Thomas; Cargill, Peter; Bradshaw, Stephen

    2016-05-01

    We use hydrodynamic modeling tools, including a two-fluid development of the EBTEL code, to investigate the properties expected of "hot" (i.e. between 106.7 and 107.2 K) non-flaring plasmas due to nanoflare heating in active regions. Here we focus on single nanoflares and show that while simple models predict an emission measure distribution extending well above 10 MK that is consistent with cooling by thermal conduction, many other effects are likely to limit the existence and detectability of such plasmas. These include: differential heating between electrons and ions, ionization non-equilibrium and, for short nanoflares, the time taken for the coronal density to increase. The most useful temperature range to look for this plasma, often called the "smoking gun" of nanoflare heating, lies between 1 MK and 10 MK. Signatures of the actual heating may be detectable in some instances.

  12. Impact of combined hydrogen plasma and transient heat loads on the performance of tungsten as plasma facing material

    NASA Astrophysics Data System (ADS)

    Wirtz, M.; Bardin, S.; Huber, A.; Kreter, A.; Linke, J.; Morgan, T. W.; Pintsuk, G.; Reinhart, M.; Sergienko, G.; Steudel, I.; De Temmerman, G.; Unterberg, B.

    2015-11-01

    Experiments were performed in three different facilities in order to investigate the impact of combined steady state deuterium plasma exposure and ELM-like thermal shock events on the performance of ultra high purity tungsten. The electron beam facility JUDITH 1 was used to simulate pure thermal loads. In addition the linear plasma devices PSI-2 and Pilot-PSI have been used for successive as well as simultaneous exposure where the transient heat loads were applied by a high energy laser and the pulsed plasma operation, respectively. The results show that the damage behaviour strongly depends on the loading conditions and the sequence of the particle and heat flux exposure. This is due to hydrogen embrittlement and/or a higher defect concentration in the tungsten near surface region due to supersaturation of hydrogen. The different results in terms of damage formation from both linear plasma devices indicate that also the plasma parameters such as particle energy, flux and fluence, plasma impurities and the pulse shape have a strong influence on the damage performance. In addition, the different loading methods such as the scanning with the electron beam in contrast to the homogeneous exposure by the laser leads to an faster increase of the surface roughness due to plastic deformation.

  13. Anisotropic universe with anisotropic sources

    SciTech Connect

    Aluri, Pavan K.; Panda, Sukanta; Sharma, Manabendra; Thakur, Snigdha E-mail: sukanta@iiserb.ac.in E-mail: snigdha@iiserb.ac.in

    2013-12-01

    We analyze the state space of a Bianchi-I universe with anisotropic sources. Here we consider an extended state space which includes null geodesics in this background. The evolution equations for all the state observables are derived. Dynamical systems approach is used to study the evolution of these equations. The asymptotic stable fixed points for all the evolution equations are found. We also check our analytic results with numerical analysis of these dynamical equations. The evolution of the state observables are studied both in cosmic time and using a dimensionless time variable. Then we repeat the same analysis with a more realistic scenario, adding the isotropic (dust like dark) matter and a cosmological constant (dark energy) to our anisotropic sources, to study their co-evolution. The universe now approaches a de Sitter space asymptotically dominated by the cosmological constant. The cosmic microwave background anisotropy maps due to shear are also generated in this scenario, assuming that the universe contains anisotropic matter along with the usual (dark) matter and vacuum (dark) energy since decoupling. We find that they contribute dominantly to the CMB quadrupole. We also constrain the current level of anisotropy and also search for any cosmic preferred axis present in the data. We use the Union 2 Supernovae data to this extent. An anisotropy axis close to the mirror symmetry axis seen in the cosmic microwave background data from Planck probe is found.

  14. Multiple Ionization Of Metal Ions By ECR Heating Of Electrons In Vacuum Arc Plasmas

    NASA Astrophysics Data System (ADS)

    Vodopyanov, A. V.; Golubev, S. V.; Mansfeld, D. A.; Nikolaev, A. G.; Oks, E. M.; Razin, S. V.; Savkin, K. P.

    2005-03-01

    A joint research and development effort has been initiated, whose ultimate goal is the enhancement the mean ion charge states in vacuum arc metal plasmas by a combination of a vacuum arc discharge and an electron cyclotron resonance (ECR) heating. Metal plasma was generated by a special vacuum arc mini-gun and injected into mirror magnetic trap. Plasma was pumped by high frequency gyrotron-generated microwave radiation (frequency 37.5 GHz, max power 100 kW, pulse duration 1.5 ms). Using of powerful microwaves makes it possible to sustain sufficient temperature of electrons needed for multiple ionizations at high plasma density (more then 1013 cm-3). Parameter of multiple ionization efficiency Neτi, where Ne is plasma density, τi, is ion lifetime, in such a case could reach rather high value ˜109 cm-3-s. In our situation τi = Ltrap/Vi, where Ltrap is trap length, Vi is plasma gun flow velocity. The results have demonstrated substantial multiple ionization of metal ions (including metals with high melting temperature). For a metal (lead, platinum) plasma, ECR heating shifted the average ion charge up to 5+. Further increase of the ion charge states will be attained by increasing the vacuum arc plasma density and optimizing the ECR heating conditions.

  15. Simulating Electron Cyclotron Resonance Heating in Kinetic and Dielectric Plasma Models with VORPAL

    NASA Astrophysics Data System (ADS)

    Roark, Christine; Smithe, David; Stoltz, Peter; Tech-X Corporation Team

    2011-10-01

    We present results of electron cyclotron resonance heating (ECRH) in a plasma sustained by microwaves using VORPAL. Specifically, we look at the electron temperature, sheath size, rate of plasma formation and power absorbed for simulations with an argon gas at 10s of mTorr pressure and 2.45 GHz. We look at the effects of including elastic, inelastic and ionizing Monte Carlo collisions on the formation of the kinetic plasma. We also discuss the use of higher-order particle algorithms for smoothing out the particle current and charge which can help reduce unphysical heating in PIC simulations of high pressure, low temperature plasmas and the effect this has on sheath size and electron temperature. We then compare these simulations to a method replacing the kinetic particles with an equivalent plasma dielectric model.

  16. Numerical Simulation of the Self-Heating Effect Induced by Electron Beam Plasma in Atmosphere

    NASA Astrophysics Data System (ADS)

    Deng, Yongfeng; Tan, Chang; Han, Xianwei; Tan, Yonghua

    2012-02-01

    For exploiting advantages of electron beam air plasma in some unusual applications, a Monte Carlo (MC) model coupled with heat transfer model is established to simulate the characteristics of electron beam air plasma by considering the self-heating effect. Based on the model, the electron beam induced temperature field and the related plasma properties are investigated. The results indicate that a nonuniform temperature field is formed in the electron beam plasma region and the average temperature is of the order of 600 K. Moreover, much larger volume pear-shaped electron beam plasma is produced in hot state rather than in cold state. The beam ranges can, with beam energies of 75 keV and 80 keV, exceed 1.0 m and 1.2 m in air at pressure of 100 torr, respectively. Finally, a well verified formula is obtained for calculating the range of high energy electron beam in atmosphere.

  17. Inflammatory cytokines and plasma redox status responses in hypertensive subjects after heat exposure

    PubMed Central

    Fonseca, S.F.; Mendonça, V.A.; Teles, M.C.; Ribeiro, V.G.C.; Tossige-Gomes, R.; Neves, C.D.C.; Rocha-Vieira, E.; Leite, L.H.R.; Soares, D.D.; Coimbra, C.C.; Lacerda, A.C.R.

    2016-01-01

    Hypertension is characterized by a pro-inflammatory status, including redox imbalance and increased levels of pro-inflammatory cytokines, which may be exacerbated after heat exposure. However, the effects of heat exposure, specifically in individuals with inflammatory chronic diseases such as hypertension, are complex and not well understood. This study compared the effects of heat exposure on plasma cytokine levels and redox status parameters in 8 hypertensive (H) and 8 normotensive (N) subjects (age: 46.5±1.3 and 45.6±1.4 years old, body mass index: 25.8±0.8 and 25.6±0.6 kg/m2, mean arterial pressure: 98.0±2.8 and 86.0±2.3 mmHg, respectively). They remained at rest in a sitting position for 10 min in a thermoneutral environment (22°C) followed by 30 min in a heated environmental chamber (38°C and 60% relative humidity). Blood samples were collected before and after heat exposure. Plasma cytokine levels were measured using sandwich ELISA kits. Plasma redox status was determined by thiobarbituric acid reactive substances (TBARS) levels and ferric reducing ability of plasma (FRAP). Hypertensive subjects showed higher plasma levels of IL-10 at baseline (P<0.05), although levels of this cytokine were similar between groups after heat exposure. Moreover, after heat exposure, hypertensive individuals showed higher plasma levels of soluble TNF receptor (sTNFR1) and lower TBARS (P<0.01) and FRAP (P<0.05) levels. Controlled hypertensive subjects, who use angiotensin-converting-enzyme inhibitor (ACE inhibitors), present an anti-inflammatory status and balanced redox status. Nevertheless, exposure to a heat stress condition seems to cause an imbalance in the redox status and an unregulated inflammatory response. PMID:26840715

  18. Self-diffusion in a stochastically heated two-dimensional dusty plasma

    NASA Astrophysics Data System (ADS)

    Sheridan, T. E.

    2016-09-01

    Diffusion in a two-dimensional dusty plasma liquid (i.e., a Yukawa liquid) is studied experimentally. The dusty plasma liquid is heated stochastically by a surrounding three-dimensional toroidal dusty plasma gas which acts as a thermal reservoir. The measured dust velocity distribution functions are isotropic Maxwellians, giving a well-defined kinetic temperature. The mean-square displacement for dust particles is found to increase linearly with time, indicating normal diffusion. The measured diffusion coefficients increase approximately linearly with temperature. The effective collision rate is dominated by collective dust–dust interactions rather than neutral gas drag, and is comparable to the dusty-plasma frequency.

  19. Overstability of acoustic waves in strongly magnetized anisotropic magnetohydrodynamic shear flows

    SciTech Connect

    Uchava, E. S.; Shergelashvili, B. M.; Tevzadze, A. G.; Poedts, S.

    2014-08-15

    We present a linear stability analysis of the perturbation modes in anisotropic magnetohydrodynamic (MHD) flows with velocity shear and strong magnetic field. Collisionless or weakly collisional plasma is described within the 16-momentum MHD fluid closure model that takes into account not only the effect of pressure anisotropy but also the effect of anisotropic heat fluxes. In this model, the low frequency acoustic wave is revealed into a standard acoustic mode and higher frequency fast thermo-acoustic and lower frequency slow thermo-acoustic waves. It is shown that thermo-acoustic waves become unstable and grow exponentially when the heat flux parameter exceeds some critical value. It seems that velocity shear makes thermo-acoustic waves overstable even at subcritical heat flux parameters. Thus, when the effect of heat fluxes is not profound acoustic waves will grow due to the velocity shear, while at supercritical heat fluxes the flow reveals compressible thermal instability. Anisotropic thermal instability should be also important in astrophysical environments, where it will limit the maximal value of magnetic field that a low density ionized anisotropic flow can sustain.

  20. Charging and Heating Dynamics of Nanoparticles in Nonthermal Plasmas

    SciTech Connect

    Kortshagen, Uwe R.

    2014-08-15

    The focus of this award was to understand the interactions of nanometer-sized particles with ionized gases, also called plasmas. Plasmas are widely used in the fabrication of electronic circuits such as microprocessors and memory devices, in plasma display panels, as well as in medical applications. Recently, these ionized gases are finding applications in the synthesis of advanced nanomaterials with novel properties, which are based on nanometer-sized particulate (nanoparticles) building blocks. As these nanoparticles grow in the plasma environment, they interact with the plasmas species such as electrons and ions which critically determines the nanoparticle properties. The University of Minnesota researchers conducting this project performed numerical simulations and developed analytical models that described the interaction of plasma-bound nanoparticles with the plasma ions. The plasma ions bombard the nanoparticle surface with substantial energy, which can result in the rearrangement of the nanoparticles’ atoms, giving them often desirable structures at the atomic scale. Being able to tune the ion energies allows to control the properties of nanoparticles produced in order to tailor their attributes for certain applications. For instance, when used in high efficiency light emitting devices, nanoparticles produced under high fluxes of highly energetic ions may show superior light emission to particles produced under low fluxes of less energetic ions. The analytical models developed by the University of Minnesota researchers enable the research community to easily determine the energy of ions bombarding the nanoparticles. The researchers extensively tested the validity of the analytical models by comparing them to sophisticated computer simulations based on stochastic particle modeling, also called Monte Carlo modeling, which simulated the motion of hundreds of thousands of ions and their interaction with the nanoparticle surfaces. Beyond the scientific

  1. Low energy, high power hydrogen neutral beam for plasma heating

    NASA Astrophysics Data System (ADS)

    Deichuli, P.; Davydenko, V.; Ivanov, A.; Korepanov, S.; Mishagin, V.; Smirnov, A.; Sorokin, A.; Stupishin, N.

    2015-11-01

    A high power, relatively low energy neutral beam injector was developed to upgrade of the neutral beam system of the gas dynamic trap device and C2-U experiment. The ion source of the injector produces a proton beam with the particle energy of 15 keV, current of up to 175 A, and pulse duration of a few milliseconds. The plasma emitter of the ion source is produced by superimposing highly ionized plasma jets from an array of four arc-discharge plasma generators. A multipole magnetic field produced with permanent magnets at the periphery of the plasma box is used to increase the efficiency and improve the uniformity of the plasma emitter. Multi-slit grids with 48% transparency are fabricated from bronze plates, which are spherically shaped to provide geometrical beam focusing. The focal length of the Ion Optical System (IOS) is 3.5 m and the initial beam diameter is 34 cm. The IOS geometry and grid potentials were optimized numerically to ensure accurate beam formation. The measured angular divergences of the beam are ±0.01 rad parallel to the slits and ±0.03 rad in the transverse direction.

  2. Low energy, high power hydrogen neutral beam for plasma heating.

    PubMed

    Deichuli, P; Davydenko, V; Ivanov, A; Korepanov, S; Mishagin, V; Smirnov, A; Sorokin, A; Stupishin, N

    2015-11-01

    A high power, relatively low energy neutral beam injector was developed to upgrade of the neutral beam system of the gas dynamic trap device and C2-U experiment. The ion source of the injector produces a proton beam with the particle energy of 15 keV, current of up to 175 A, and pulse duration of a few milliseconds. The plasma emitter of the ion source is produced by superimposing highly ionized plasma jets from an array of four arc-discharge plasma generators. A multipole magnetic field produced with permanent magnets at the periphery of the plasma box is used to increase the efficiency and improve the uniformity of the plasma emitter. Multi-slit grids with 48% transparency are fabricated from bronze plates, which are spherically shaped to provide geometrical beam focusing. The focal length of the Ion Optical System (IOS) is 3.5 m and the initial beam diameter is 34 cm. The IOS geometry and grid potentials were optimized numerically to ensure accurate beam formation. The measured angular divergences of the beam are ±0.01 rad parallel to the slits and ±0.03 rad in the transverse direction. PMID:26628137

  3. Confinement studies of ohmically heated plasmas in TFTR

    SciTech Connect

    Efthimion, P.C.; Bretz, N.L.; Bell, M.G.; Bitter, M.; Blanchard, W.R.; Boody, F.; Boyd, D.; Bush, C.E.; Cecchi, J.L.; Coonrod, J.

    1985-03-01

    Systematic scans of density in large deuterium plasmas (a = 0.83 m) at several values of plasma current and toroidal magnetic field strength indicate that the total energy confinement time, tau/sub E/, is proportional to the line-average density anti n/sub e/ and the limiter q. Confinement times of approx. 0.3 s have been observed for anti n/sub e/ = 2.8 x 10/sup 19/ m/sup -3/. Plasma size scaling experiments with plasmas of minor radii a = 0.83, 0.69, 0.55, and 0.41 m at constant limiter q reveal a confinement dependence on minor radius. The major-radius dependence of tau/sub E/, based on a comparison between TFTR and PLT results, is consistent with R/sup 2/ scaling. From the power balance, the thermal diffusivity chi/sub e/ is found to be significantly less than the INTOR value. In the a = 0.41 m plasmas, saturation of confinement is due to neoclassical ion conduction (chi/sub i/ neoclassical >> chi/sub e/).

  4. Low energy, high power hydrogen neutral beam for plasma heating

    SciTech Connect

    Deichuli, P.; Davydenko, V.; Ivanov, A. Mishagin, V.; Sorokin, A.; Stupishin, N.; Korepanov, S.; Smirnov, A.

    2015-11-15

    A high power, relatively low energy neutral beam injector was developed to upgrade of the neutral beam system of the gas dynamic trap device and C2-U experiment. The ion source of the injector produces a proton beam with the particle energy of 15 keV, current of up to 175 A, and pulse duration of a few milliseconds. The plasma emitter of the ion source is produced by superimposing highly ionized plasma jets from an array of four arc-discharge plasma generators. A multipole magnetic field produced with permanent magnets at the periphery of the plasma box is used to increase the efficiency and improve the uniformity of the plasma emitter. Multi-slit grids with 48% transparency are fabricated from bronze plates, which are spherically shaped to provide geometrical beam focusing. The focal length of the Ion Optical System (IOS) is 3.5 m and the initial beam diameter is 34 cm. The IOS geometry and grid potentials were optimized numerically to ensure accurate beam formation. The measured angular divergences of the beam are ±0.01 rad parallel to the slits and ±0.03 rad in the transverse direction.

  5. The evolution of interstellar clouds in a streaming hot plasma including heat conduction

    NASA Astrophysics Data System (ADS)

    Vieser, W.; Hensler, G.

    2007-09-01

    Context: The interstellar medium contains warm clouds that are embedded in a hot dilute gas produced by supernovae. Because both gas phases are in contact, an interface forms where mass and energy are exchanged. Whether heat conduction leads to evaporation of these clouds or whether condensation dominates has been analytically derived. Both phases behave differently dynamically so that their relative motion has to be taken into account. Aims: Real clouds in static conditions that experience saturated heat conduction are stabilized against evaporation if self-gravity and cooling play a role. Here, we investigte to what extent heat conduction can hamper the dynamical disruption of clouds embedded in a streaming hot plasma. Methods: To examine the evolution of giant molecular clouds in the stream of a hot plasma we performed two-dimensional hydrodynamical simulations that take full account of self-gravity, heating and cooling effects and heat conduction by electrons. We use the thermal conductivity of a fully ionized hydrogen plasma proposed by Spitzer and a saturated heat flux according to Cowie & McKee in regions where the mean free path of the electrons is large compared to the temperature scaleheight. Results: Significant structural and evolutionary differences occur between simulations with and without heat conduction. Dense clouds in pure dynamical models experience dynamical destruction by Kelvin-Helmholtz (KH) instability. In static models heat conduction leads to evaporation of such clouds. Heat conduction acting on clouds in a gas stream smooths out steep temperature and density gradients at the edge of the cloud because the conduction timescale is shorter than the cooling timescale. This diminishes the velocity gradient between the streaming plasma and the cloud, so that the timescale for the onset of KH instabilities increases, and the surface of the cloud becomes less susceptible to KH instabilities. The stabilisation effect of heat conduction against KH

  6. Daytime Solar Heating of Photovoltaic Arrays in Low Density Plasmas

    NASA Technical Reports Server (NTRS)

    Galofaro, J.; Vayner, B.; Ferguson, D.

    2003-01-01

    The purpose of the current work is to determine the out-gassing rate of H2O molecules for a solar array placed under daytime solar heating (full sunlight) conditions typically encountered in a Low Earth Orbital (LEO) environment. Arc rates are established for individual arrays held at 14 C and are used as a baseline for future comparisons. Radiated thermal solar flux incident to the array is simulated by mounting a stainless steel panel equipped with resistive heating elements several centimeters behind the array. A thermal plot of the heater plate temperature and the array temperature as a function of heating time is then obtained. A mass spectrometer is used to record the levels of partial pressure of water vapor in the test chamber after each of the 5 heating/cooling cycles. Each of the heating cycles was set to time duration of 40 minutes to simulate the daytime solar heat flux to the array over a single orbit. Finally the array is cooled back to ambient temperature after 5 complete cycles and the arc rates of the solar arrays is retested. A comparison of the various data is presented with rather some unexpected results.

  7. Energy distribution and heat transfer mechanisms in atmospheric pressure non-equilibrium plasmas

    NASA Astrophysics Data System (ADS)

    Nozaki, Tomohiro; Miyazaki, Yu; Unno, Yasuko; Okazaki, Ken

    2001-12-01

    Energy distribution and heat transfer mechanisms in atmospheric pressure non-equilibrium plasmas were investigated extensively through energy balance analysis, emission spectroscopy of the rotational band of CH (A2Δ→X2Π), and gas chromatographic analysis. Two plasma sources were examined: methane-fed dielectric barrier discharge (DBD) and atmospheric pressure glow-discharge (APG). The DBD features filamentary microdischarges accompanied by surface discharge along a dielectric barrier. As a result, 60% of the input power was measured as heat transfer to the dielectric electrode, whereas 20% was to the metallic electrode. Consequently, feed gas average temperature was increased only by 20-40 K. On the other hand, rotational temperature of the corresponding emission region exceeded average gas temperature by 100 K. In APG, heat transfer to electrodes was dominated by formation of negative glow regardless of whether the electrode was covered by a dielectric. However, negative glow tended to be thinner and more intense when it formed on a metallic electrode, leading to slightly higher metallic heating. Rotational temperature in APG was close to average gas temperature since APG does not show radial localization of plasma. Energy efficiency for methane decomposition process to produce ethane, ethylene, and hydrogen was about 1% regardless of the plasma source. Energy distribution and heat transfer mechanisms depend strongly on the plasma spatial structure rather than flow fields or feed gas physical properties.

  8. On RF heating of inhomogeneous collisional plasma under ion-cyclotron resonance conditions

    SciTech Connect

    Timofeev, A. V.

    2015-11-15

    During ion-cyclotron resonance (ICR) heating of plasma by the magnetic beach method, as well as in some other versions of ICR heating, it is necessary to excite Alfvén oscillations. In this case, it is difficult to avoid the phenomenon of the Alfvén resonance, in which Alfvén oscillations transform into lower hybrid oscillations. The latter efficiently interact with electrons, due to which most of the deposited RF energy is spent on electron (rather than ion) heating. The Alfvén resonance takes place due to plasma inhomogeneity across the external magnetic field. Therefore, it could be expected that variations in the plasma density profile would substantially affect the efficiency of the interaction of RF fields with charged particles. However, the results obtained for different plasma density profiles proved to be nearly the same. In the present work, a plasma is considered the parameters of which correspond to those planned in future ICR plasma heating experiments on the PS-1 facility at the Kurchatov Institute. When analyzing the interaction of RF fields with charged particles, both the collisionless resonance interaction and the interaction caused by Coulomb collisions are taken into account, because, in those experiments, the Coulomb collision frequency will be comparable with the frequency of the heating field. Antennas used for ICR heating excite RF oscillations with a wide spectrum of wavenumbers along the magnetic field. After averaging over the spectrum, the absorbed RF energy calculated with allowance for collisions turns out to be close to that absorbed in collisionless plasma, the energy fraction absorbed by electrons being substantially larger than that absorbed by ions.

  9. Predictions of Alpha Heating in ITER L-mode and H-mode Plasmas

    SciTech Connect

    R.V. Budny

    2011-01-06

    Predictions of alpha heating in L-mode and H-mode DT plasmas in ITER are generated using the PTRANSP code. The baseline toroidal field of 5.3 T, plasma current ramped to 15 MA and a flat electron density profile ramped to Greenwald fraction 0.85 are assumed. Various combinations of external heating by negative ion neutral beam injection, ion cyclotron resonance, and electron cyclotron resonance are assumed to start half-way up the density ramp. The time evolution of plasma temperatures and, for some cases, toroidal rotation are predicted assuming GLF23 and boundary parameters. Significant toroidal rotation and flow-shearing rates are predicted by GLF23 even in the L-mode phase with low boundary temperatures, and the alpha heating power is predicted to be significant if the power threshold for the transition to H-mode is higher than the planned total heating power. The alpha heating is predicted to be 8-76 MW in L-mode at full density. External heating mixes with higher beam injection power have higher alpha heating power. Alternatively if the toroidal rotation is predicted assuming that the ratio of the momentum to thermal ion energy conductivity is 0.5, the flow-shearing rate is predicted to have insignificant effects on the GLF23- predicted temperatures, and alpha heating is predicted to be 8-20 MW. In H-mode plasmas the alpha heating is predicted to depend sensitively on the assumed pedestal temperatures. Cases with fusion gain greater than 10 are predicted to have alpha heating greater than 80 MW.

  10. Spatiotemporal study of gas heating mechanisms in a radio-frequency electrothermal plasma micro-thruster

    NASA Astrophysics Data System (ADS)

    Greig, Amelia; Charles, Christine; Boswell, Roderick

    2015-10-01

    A spatiotemporal study of neutral gas temperature during the first 100 s of operation for a radio-frequency electrothermal plasma micro-thruster operating on nitrogen at 60 W and 1.5 Torr is performed to identify the heating mechanisms involved. Neutral gas temperature is estimated from rovibrational band fitting of the nitrogen second positive system. A set of baffles are used to restrict the optical image and separate the heating mechanisms occurring in the central bulk discharge region and near the thruster walls. For each spatial region there are three distinct gas heating mechanisms being fast heating from ion-neutral collisions with timescales of tens of milliseconds, intermediate heating with timescales of 10 s from ion bombardment on the inner thruster tube surface creating wall heating, and slow heating with timescales of 100 s from gradual warming of the entire thruster housing. The results are discussed in relation to optimising the thermal properties of future thruster designs.

  11. Reduction of trapped-ion anomalous heating by in situ surface plasma cleaning

    NASA Astrophysics Data System (ADS)

    McConnell, Robert; Bruzewicz, Colin; Chiaverini, John; Sage, Jeremy

    2015-08-01

    Anomalous motional heating is a major obstacle to scalable quantum information processing with trapped ions. Although the source of this heating is not yet understood, several previous studies suggest that noise due to surface contaminants is the limiting heating mechanism in some instances. We demonstrate an improvement by a factor of 4 in the room-temperature heating rate of a niobium surface electrode trap by in situ plasma cleaning of the trap surface. This surface treatment was performed with a simple homebuilt coil assembly and commercially available matching network and is considerably gentler than other treatments, such as ion milling or laser cleaning, that have previously been shown to improve ion heating rates. We do not see an improvement in the heating rate when the trap is operated at cryogenic temperatures, pointing to a role of thermally activated surface contaminants in motional heating whose activity may freeze out at low temperatures.

  12. Beam heated linear theta-pinch device for producing hot plasmas

    DOEpatents

    Bohachevsky, Ihor O.

    1981-01-01

    A device for producing hot plasmas comprising a single turn theta-pinch coil, a fast discharge capacitor bank connected to the coil, a fuel element disposed along the center axis of the coil, a predetermined gas disposed within the theta-pinch coil, and a high power photon, electron or ion beam generator concentrically aligned to the theta-pinch coil. Discharge of the capacitor bank generates a cylindrical plasma sheath within the theta-pinch coil which heats the outer layer of the fuel element to form a fuel element plasma layer. The beam deposits energy in either the cylindrical plasma sheath or the fuel element plasma layer to assist the implosion of the fuel element to produce a hot plasma.

  13. Complete anisotropic time-dependent heat equation in KTP crystal under repetitively pulsed Gaussian beams: a numerical approach.

    PubMed

    Rezaee, Mostafa Mohammad; Sabaeian, Mohammad; Motazedian, Alireza; Jalil-Abadi, Fatemeh Sedaghat; Khaldi-Nasab, Ali

    2015-02-20

    In this work, a thorough and detailed solution for the time-dependent heat equation for a cylindrical nonlinear potassium titanyl phosphate (KTP) crystal under a repetitively pulsed pumping source is developed. The convection and radiation boundary conditions, which are usually ignored in the literature, have been taken into account, and their importance on the temperature distribution has been discussed in detail. Moreover, the temperature dependence of thermal conductivity of KTP was considered in the calculations, and its impact is discussed. It is shown that the radiation term has a negligible effect and can be dropped safely, while the temperature dependence of thermal conductivity is more influential, such that ignorance of it brings some errors into the modeling. The time evolution of the temperature while the crystal is pumping with a train of successive Gaussian pulses until reaching equilibrium is shown. To accomplish numerical calculations, we developed a homemade code written with the finite difference time domain method in Intel Fortran (ifort) and ran it with the Linux operating system. PMID:25968183

  14. Rapid heating of a strongly coupled plasma at the solid-liquid phase transition

    NASA Astrophysics Data System (ADS)

    Jensen, M. J.; Hasegawa, T.; Bollinger, J. J.; Dubin, D. H. E.

    2004-11-01

    Between 10^4 and 10^6 ^9Be^+ ions are trapped in a 4.5 Tesla Penning trap and laser-cooled to ˜1 mK, where the ions form a crystalline plasma with an interparticle spacing of ˜20 μm. This system is a realization of a strongly coupled one-component plasma. Using Doppler laser spectroscopy on a single-photon transition, we measured the temperature and heating rate of this plasma when not being laser-cooled. We measured a slow heating rate of ≤ 100 mK/s due to residual gas collisions for the first 100-200 ms after turning off the cooling laser. This slow heating is followed by a rapid heating to 1-2 K in 100 ms as the plasma undergoes the solid-liquid phase transition at T=10 mK (Γ ˜ 170). We will present evidence that this rapid heating is due to a sudden release of energy from weakly cooled degrees of freedom involving the cyclotron motion of trapped impurity ions. We will also discuss the prospects for observing the latent heat associated with the phase transition.

  15. Characterization of Heat-Wave Propagation through Laser-Driven Ti-Doped Underdense Plasma

    SciTech Connect

    Tanabe, M; Nishimura, H; Ohnishi, N; Fournier, K B; Fujioka, S; Iwamae, A; Hansen, S B; Nagai, K; Girard, F; Primout, M; Villette, B; Brebion, D; Mima, K

    2009-02-23

    The propagation of a laser-driven heat-wave into a Ti-doped aerogel target was investigated. The temporal evolution of the electron temperature was derived by means of Ti K-shell x-ray spectroscopy, and compared with two-dimensional radiation hydrodynamic simulations. Reasonable agreement was obtained in the early stage of the heat-wave propagation. In the later phase, laser absorption, the propagation of the heat wave, and hydrodynamic motion interact in a complex manner, and the plasma is mostly re-heated by collision and stagnation at the target central axis.

  16. Fast-electron refluxing effects on anisotropic hard-x-ray emission from intense laser-plasma interactions.

    PubMed

    McKeever, K; Makita, M; Nersisyan, G; Dzelzainis, T; White, S; Kettle, B; Dromey, B; Zepf, M; Sarri, G; Doria, D; Ahmed, H; Lewis, C L S; Riley, D; Robinson, A P L

    2015-03-01

    Fast-electron generation and dynamics, including electron refluxing, is at the core of understanding high-intensity laser-plasma interactions. This field is itself of strong relevance to fast ignition fusion and the development of new short-pulse, intense, x-ray, γ-ray, and particle sources. In this paper, we describe experiments that explicitly link fast-electron refluxing and anisotropy in hard-x-ray emission. We find the anisotropy in x-ray emission to be strongly correlated to the suppression of refluxing. In contrast to some previous work, the peak of emission is directly along the rear normal to the target rather than along either the incident laser direction or the specular reflection direction. PMID:25871224

  17. Deposition of Hard Chrome Coating onto Heat Susceptible Substrates by Low Power Microwave Plasma Spray

    NASA Astrophysics Data System (ADS)

    Redza, Ahmad; Yasui, Toshiaki; Fukumoto, Masahiro

    2016-02-01

    Microwave plasma spray requires relatively low power, which is lower than 1 kW in comparison to other plasma spraying method. Until now, we are able to deposit Cu and Hydroxyapatite coating onto heat susceptible substrate, CFRP which are difficult for conventional plasma spray due to the excessive heat input. In this paper, a hard chromium coating was deposited onto SUS304 and CFRP by a low power microwave plasma spray technique. By controlling the working gas flow rate and spraying distance, a hard chrome coating with thickness of approximately 30 μm was successfully deposited onto CFRP substrate with hardness of 1110 Hv0.05. Furthermore, the coating produced here is higher than that produced by hard chrome plating.

  18. Fabrication of High-Temperature Heat Exchangers by Plasma Spraying Exterior Skins on Nickel Foams

    NASA Astrophysics Data System (ADS)

    Hafeez, P.; Yugeswaran, S.; Chandra, S.; Mostaghimi, J.; Coyle, T. W.

    2016-05-01

    Thermal-sprayed heat exchangers were tested at high temperatures (750 °C), and their performances were compared to the foam heat exchangers made by brazing Inconel sheets to their surface. Nickel foil was brazed to the exterior surface of 10-mm-thick layers of 10 and 40 PPI nickel foam. A plasma torch was used to spray an Inconel coating on the surface of the foil. A burner test rig was built to produce hot combustion gases that flowed over exposed face of the heat exchanger. Cooling air flowed through the foam heat exchanger at rates of up to 200 SLPM. Surface temperature and air inlet/exit temperature were measured. Heat transfer to air flowing through the foam was significantly higher for the thermally sprayed heat exchangers than for the brazed heat exchangers. On an average, thermally sprayed heat exchangers show 36% higher heat transfer than conventionally brazed foam heat exchangers. At low flow rates, the convective resistance is large (~4 × 10-2 m2 K/W), and the effect of thermal contact resistance is negligible. At higher flow rates, the convective resistance decreases (~2 × 10-3 m2 K/W), and the lower contact resistance of the thermally sprayed heat exchanger provides better performance than the brazed heat exchangers.

  19. Fabrication of High-Temperature Heat Exchangers by Plasma Spraying Exterior Skins on Nickel Foams

    NASA Astrophysics Data System (ADS)

    Hafeez, P.; Yugeswaran, S.; Chandra, S.; Mostaghimi, J.; Coyle, T. W.

    2016-06-01

    Thermal-sprayed heat exchangers were tested at high temperatures (750 °C), and their performances were compared to the foam heat exchangers made by brazing Inconel sheets to their surface. Nickel foil was brazed to the exterior surface of 10-mm-thick layers of 10 and 40 PPI nickel foam. A plasma torch was used to spray an Inconel coating on the surface of the foil. A burner test rig was built to produce hot combustion gases that flowed over exposed face of the heat exchanger. Cooling air flowed through the foam heat exchanger at rates of up to 200 SLPM. Surface temperature and air inlet/exit temperature were measured. Heat transfer to air flowing through the foam was significantly higher for the thermally sprayed heat exchangers than for the brazed heat exchangers. On an average, thermally sprayed heat exchangers show 36% higher heat transfer than conventionally brazed foam heat exchangers. At low flow rates, the convective resistance is large (~4 × 10-2 m2 K/W), and the effect of thermal contact resistance is negligible. At higher flow rates, the convective resistance decreases (~2 × 10-3 m2 K/W), and the lower contact resistance of the thermally sprayed heat exchanger provides better performance than the brazed heat exchangers.

  20. Production of a large diameter hot-electron plasma by electron cyclotron resonance heating

    SciTech Connect

    Kawai, Y.; Sakamoto, K.

    1982-05-01

    A large diameter hot-electron plasma is produced by electron cyclotron resonance heating, using a slotted Lisitano coil as a launcher. It is found from detailed measurements of the plasma parameters that n/sub e/< or approx. =3 x 10/sup 11/ cm/sup -3/ and T/sub e/< or approx. =40 eV, with a diameter roughly-equal14 cm. High-energy tails with temperatures of more than 100 eV are observed.

  1. Production of a large diameter hot-electron plasma by electron cyclotron resonance heating

    NASA Astrophysics Data System (ADS)

    Kawai, Y.; Sakamoto, K.

    1982-05-01

    A large diameter hot-electron plasma is produced by electron cyclotron resonance heating, using a slotted Lisitano coil as a launcher. It is found from detailed measurements of the plasma parameters that ne≲3×1011 cm-3 and Te≲40 eV, with a diameter ≊14 cm. High-energy tails with temperatures of more than 100 eV are observed.

  2. A quantitative model for heat pulse propagation across large helical device plasmas

    NASA Astrophysics Data System (ADS)

    Zhu, H.; Dendy, R. O.; Chapman, S. C.; Inagaki, S.

    2015-06-01

    It is known that rapid edge cooling of magnetically confined plasmas can trigger heat pulses that propagate rapidly inward. These can result in large excursion, either positive or negative, in the electron temperature at the core. A set of particularly detailed measurements was obtained in Large Helical Device (LHD) plasmas [S. Inagaki et al., Plasma Phys. Controlled Fusion 52, 075002 (2010)], which are considered here. By applying a travelling wave transformation, we extend the model of Dendy et al., Plasma Phys. Controlled Fusion 55, 115009 (2013), which successfully describes the local time-evolution of heat pulses in these plasmas, to include also spatial dependence. The new extended model comprises two coupled nonlinear first order differential equations for the (x, t) evolution of the deviation from steady state of two independent variables: the excess electron temperature gradient and the excess heat flux, both of which are measured in the LHD experiments. The mathematical structure of the model equations implies a formula for the pulse velocity, defined in terms of plasma quantities, which aligns with empirical expectations and is within a factor of two of the measured values. We thus model spatio-temporal pulse evolution, from first principles, in a way which yields as output the spatiotemporal evolution of the electron temperature, which is also measured in detail in the experiments. We compare the model results against LHD datasets using appropriate initial and boundary conditions. Sensitivity of this nonlinear model with respect to plasma parameters, initial conditions, and boundary conditions is also investigated. We conclude that this model is able to match experimental data for the spatio-temporal evolution of the temperature profiles of these pulses, and their propagation velocities, across a broad radial range from r /a ≃0.5 to the plasma core. The model further implies that the heat pulse may be related mathematically to soliton solutions of the

  3. Observation of Ion Acceleration and Heating during Collisionless Magnetic Reconnection in a Laboratory Plasma

    SciTech Connect

    Yoo, Jongsoo; Yamada, Masaaki; Ji, Hantao; Myers, Clayton E.

    2012-12-10

    The ion dynamics in a collisionless magnetic reconnection layer are studied in a laboratory plasma. The measured in-plane plasma potential profile, which is established by electrons accelerated around the electron diffusion region, shows a saddle-shaped structure that is wider and deeper towards the outflow direction. This potential structure ballistically accelerates ions near the separatrices toward the outflow direction. Ions are heated as they travel into the high pressure downstream region.

  4. Excitation of kinetic Alfven waves by resonant mode conversion and longitudinal heating of magnetized plasmas

    NASA Technical Reports Server (NTRS)

    Tanaka, Motohiko; Sato, Tetsuya; Hasegawa, A.

    1989-01-01

    The excitation of the kinetic Alfven wave by resonant mode conversion and longitudinal heating of the plasma by the kinetic Alfven wave were demonstrated on the basis of a macroscale particle simulation. The longitudinal electron current was shown to be cancelled by the ions. The kinetic Alfven wave produced an ordered motion of the plasma particles in the wave propagation direction. The electrons were pushed forward along the ambient magnetic field by absorbing the kinetic Alfven wave through the Landau resonance.

  5. A multi-dimensional Vlasov-Fokker-Planck code for arbitrarily anisotropic high-energy-density plasmas

    SciTech Connect

    Tzoufras, M.; Tableman, A.; Tsung, F. S.; Mori, W. B.; Bell, A. R.

    2013-05-15

    To study the kinetic physics of High-Energy-Density Laboratory Plasmas, we have developed the parallel relativistic 2D3P Vlasov-Fokker-Planck code Oshun. The numerical scheme uses a Cartesian mesh in configuration-space and incorporates a spherical harmonic expansion of the electron distribution function in momentum-space. The expansion is truncated such that the necessary angular resolution of the distribution function is retained for a given problem. Finite collisionality causes rapid decay of the high-order harmonics, thereby providing a natural truncation mechanism for the expansion. The code has both fully explicit and implicit field-solvers and employs a linearized Fokker-Planck collision operator. Oshun has been benchmarked against well-known problems, in the highly kinetic limit to model collisionless relativistic instabilities, and in the hydrodynamic limit to recover transport coefficients. The performance of the code, its applicability, and its limitations are discussed in the context of simple problems with relevance to inertial fusion energy.

  6. Collisionless electron heating in periodic arrays of inductively coupled plasmas

    SciTech Connect

    Czarnetzki, U.; Tarnev, Kh.

    2014-12-15

    A novel mechanism of collisionless heating in large planar arrays of small inductive coils operated at radio frequencies is presented. In contrast to the well-known case of non-local heating related to the transversal conductivity, when the electrons move perpendicular to the planar coil, we investigate the problem of electrons moving in a plane parallel to the coils. Two types of periodic structures are studied. Resonance velocities where heating is efficient are calculated analytically by solving the Vlasov equation. Certain scaling parameters are identified. The concept is further investigated by a single particle simulation based on the ergodic principle and combined with a Monte Carlo code allowing for collisions with Argon atoms. Resonances, energy exchange, and distribution functions are obtained. The analytical results are confirmed by the numerical simulation. Pressure and electric field dependences are studied. Stochastic heating is found to be most efficient when the electron mean free path exceeds the size of a single coil cell. Then the mean energy increases approximately exponentially with the electric field amplitude.

  7. Modeling of limiter heat loads and impurity transport in Wendelstein 7-X startup plasmas

    NASA Astrophysics Data System (ADS)

    Effenberg, Florian; Feng, Y.; Frerichs, H.; Schmitz, O.; Hoelbe, H.; Koenig, R.; Krychowiak, M.; Pedersen, T. S.; Bozhenkov, S.; Reiter, D.

    2015-11-01

    The quasi-isodynamic stellarator Wendelstein 7-X starts plasma operation in a limiter configuration. The field consists of closed magnetic flux surfaces avoiding magnetic islands in the plasma boundary. Because of the small size of the limiters and the absence of wall-protecting elements in this phase, limiter heat loads and impurity generation due to plasma surface interaction become a concern. These issues are studied with the 3D fluid plasma edge and kinetic neutral transport code EMC3-Eirene. It is shown that the 3D SOL consists of three separate helical magnetic flux bundles of different field line connection lengths. A density scan at input power of 4MW reveals a strong modulation of the plasma paramters with the connection length. The limiter peak heat fluxes drop from 14 MWm-2 down to 10 MWm-2 with raising the density from 1 ×1018m-3 to 1.9 ×1019m-3, accompanied by an increase of the heat flux channel widths λq. Radiative power losses can help to avoid thermal overloads of the limiters at the upper margin of the heating power. The power removal feasibility of the intrinsic carbon and other extrinsic light impurities via active gas injection is discussed as a preparation of this method for island divertor operation. Work supported in part by start up funds of the Department of Engineering Physics at the University of Wisconsin - Madison, USA and by the U.S. Department of Energy under grant DE-SC0013911.

  8. Development of a 100 kW plasma torch for plasma assisted combustion of low heating value fuels

    NASA Astrophysics Data System (ADS)

    Takali, S.; Fabry, F.; Rohani, V.; Cauneau, F.; Fulcheri, L.

    2014-11-01

    Most thermal power plants need an auxiliary power source to (i) heat-up the boiler during start up phases before reaching autonomy power and (ii) sustain combustion at low load. This supplementary power is commonly provided with high LHV fossil fuel burners which increases operational expenses and disables the use of anti-pollutant filters. A Promising alternative is under development and consists in high temperature plasma assisted AC electro-burners. In this paper, the development of a new 100 kW three phase plasma torch with graphite electrodes is detailed. This plasma torch is working at atmospheric pressure with air as plasma gas and has three-phase power supply and working at 680 Hz. The nominal air flow rate is 60 Nm3.h-1 and the outlet gas temperature is above 2 500 K. At the beginning, graphite electrodes erosion by oxidizing medium was studied and controlling parameters were identified through parametric set of experiments and tuned for optimal electrodes life time. Then, a new 3-phase plasma torch design was modelled and simulated on ANSYS platform. The characteristics of the plasma flow and its interaction with the environing elements of the torch are detailed hereafter.

  9. Development of fast steering mirror control system for plasma heating and diagnostics.

    PubMed

    Okada, K; Nishiura, M; Kubo, S; Shimozuma, T; Yoshimura, Y; Igami, H; Takahashi, H; Tanaka, K; Kobayashi, S; Ito, S; Mizuno, Y; Ogasawara, S

    2014-11-01

    A control system for a fast steering mirror has been newly developed for the electron cyclotron heating (ECH) launchers in the large helical device. This system enables two-dimensional scan during a plasma discharge and provides a simple feedback control function. A board mounted with a field programmable gate array chip has been designed to realize feedback control of the ECH beam position to maintain higher electron temperature by ECH. The heating position is determined by a plasma diagnostic signal related to the electron temperature such as electron cyclotron emission and Thomson scattering. PMID:25430376

  10. Induction-linac based free-electron laser amplifiers for plasma heating

    SciTech Connect

    Jong, R.A.

    1988-08-22

    We describe an induction-linac based free-electron laser amplifier that is presently under construction at the Lawrence Livermore National Laboratory. It is designed to produce up to 2 MW of average power at a frequency of 250 GHz for plasma heating experiments in the Microwave Tokamak Experiment. In addition, we shall describe a FEL amplifier design for plasma heating of advanced tokamak fusion devices. This system is designed to produce average power levels of about 10 MW at frequencies ranging form 280 to 560 GHz. 7 refs., 1 tab.

  11. Heat Transfer Between a Plasma Jet and a Metal Surface in a Cut Cavity

    NASA Astrophysics Data System (ADS)

    Veremeichik, A. N.; Sazonov, M. I.; Khvisevich, V. M.; Tsyganov, D. L.

    2015-11-01

    Investigations are presented of the formation of a plasma jet and of the current-density and heat-flux distributions in the process of metal cutting along the cut cavity with direct and reverse polarities of the plasmatron connection. The study of the specific features of heat transfer of the arc with the surface of the cut cavity was carried out on the basis of the developed plasma unit which makes it possible to model the technological process of separating metal cutting. A sectional cut model is proposed which can be used to work out and optimize the methods of determination of cutting parameters.

  12. Development of fast steering mirror control system for plasma heating and diagnostics

    SciTech Connect

    Okada, K. Kubo, S.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Takahashi, H.; Tanaka, K.; Kobayashi, S.; Ito, S.; Mizuno, Y.; Ogasawara, S.; Nishiura, M.

    2014-11-15

    A control system for a fast steering mirror has been newly developed for the electron cyclotron heating (ECH) launchers in the large helical device. This system enables two-dimensional scan during a plasma discharge and provides a simple feedback control function. A board mounted with a field programmable gate array chip has been designed to realize feedback control of the ECH beam position to maintain higher electron temperature by ECH. The heating position is determined by a plasma diagnostic signal related to the electron temperature such as electron cyclotron emission and Thomson scattering.

  13. Alpha Heating in ITER L-mode and H-mode Plasma

    SciTech Connect

    R.V. Budny

    2011-07-18

    There are many uses of predictions of ITER plasma performance. One is assessing requirements of different plasma regimes. For instance, what current drive and control are needed for steady state. The heating, current drive, and torque systems planned for initial DT operation are negative ion neutral beam injection (NB), ion cyclotron resonance (IC), and electron cyclotron resonance (EC). Which combinations of heating are optimal. What are benefits of the torques, current drive, and fueling using NB. What are the shine-through power and optimum voltage for the NB? What are optimal locations and aiming of the EC launchers? Another application is nuclear licensing (e.g. System integrity, how many neutrons).

  14. Ion cyclotron range of frequencies heating and current drive in deuterium-tritium plasmas

    NASA Astrophysics Data System (ADS)

    Phillips, C. K.; Bell, M. G.; Bell, R.; Bretz, N.; Budny, R. V.; Darrow, D. S.; Grek, B.; Hammett, G.; Hosea, J. C.; Hsuan, H.; Ignat, D.; Majeski, R.; Mazzucato, E.; Nazikian, R.; Park, H.; Rogers, J. H.; Schilling, G.; Stevens, J. E.; Synakowski, E.; Taylor, G.; Wilson, J. R.; Zarnstorff, M. C.; Zweben, S. J.; Bush, C. E.; Goldfinger, R.; Jaeger, E. F.; Murakami, M.; Rasmussen, D.; Bettenhausen, M.; Lam, N. T.; Scharer, J.; Sund, R.; Sauter, O.

    1995-06-01

    The first experiments utilizing high-power radio waves in the ion cyclotron range of frequencies to heat deuterium-tritium (D-T) plasmas have been completed on the Tokamak Fusion Test Reactor [Fusion Technol. 21, 13 (1992)]. Results from the initial series of experiments have demonstrated efficient core second harmonic tritium (2ΩT) heating in parameter regimes approaching those anticipated for the International Thermonuclear Experimental Reactor [D. E. Post, Plasma Physics and Controlled Nuclear Fusion Research, Proceedings of the 13th International Conference, Washington, DC, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 239]. Observations are consistent with modeling predictions for these plasmas. Efficient electron heating via mode conversion of fast waves to ion Bernstein waves has been observed in D-T, deuterium-deuterium (D-D), and deuterium-helium-4 (D-4He) plasmas with high concentrations of minority helium-3 (3He) (n3He/ne≳10%). Mode conversion current drive in D-T plasmas was simulated with experiments conducted in D-3He-4He plasmas. Results show a directed propagation of the mode converted ion Bernstein waves, in correlation with the antenna phasing.

  15. PLASMA HEATING IN THE VERY EARLY AND DECAY PHASES OF SOLAR FLARES

    SciTech Connect

    Falewicz, R.; Rudawy, P.; Siarkowski, M. E-mail: rudawy@astro.uni.wroc.pl

    2011-05-20

    In this paper, we analyze the energy budgets of two single-loop solar flares under the assumption that non-thermal electrons (NTEs) are the only source of plasma heating during all phases of both events. The flares were observed by RHESSI and GOES on 2002 September 20 and 2002 March 17, respectively. For both investigated flares we derived the energy fluxes contained in NTE beams from the RHESSI observational data constrained by observed GOES light curves. We showed that energy delivered by NTEs was fully sufficient to fulfill the energy budgets of the plasma during the pre-heating and impulsive phases of both flares as well as during the decay phase of one of them. We concluded that in the case of the investigated flares there was no need to use any additional ad hoc heating mechanisms other than heating by NTEs.

  16. Blood volume and plasma protein responses to heat acclimatization in humans

    SciTech Connect

    Harrison, M.H.; Edwards, R.J.; Graveney, M.J.; Cochrane, L.A.; Davies, J.A.

    1981-03-01

    The effects of heat acclimatization on intravascular volume and protein responses to acute heat stress and exercise were studied in six male subjects. Absolute values for hematocrit and hemoglobin concentration were lower after acclimatization, indicating hemodilution. Also, after acclimatization, the magnitude of the hemoconcentration response to exercise in the heat was significantly increased. There was no change in the concentration of plasma protein during or after acclimatization compared with before acclimatization, but there was a net increase in the total intravascular protein content. It is suggested that the hemodilution associated with heat acclimatization may be explained in terms of an increase in the intravascular oncotic pressure following an exercise-induced augmentation of protein, occurring at the expense of the interstitial compartment. It is concluded that this hemodilution is unlikely to be primarily responsible for the cardiovascular adjustment accompanying heat acclimatization and that it should be regarded as a secondary feature of adaptation to heat.

  17. Quasi-linear heating and acceleration in bi-Maxwellian plasmas

    SciTech Connect

    Hellinger, Petr; Trávníček, Pavel M.

    2013-12-15

    Quasi-linear acceleration and heating rates are derived for drifting bi-Maxwellian distribution functions in a general nonrelativistic case for arbitrary wave vectors, propagation angles, and growth/damping rates. The heating rates in a proton-electron plasma due to ion-cyclotron/kinetic Alfvén and mirror waves for a wide range of wavelengths, directions of propagation, and growth or damping rates are explicitly computed.

  18. Plasma measurements of the Pioneer Venus Orbiter in the Venus ionosheath - Evidence for plasma heating near the ionopause

    NASA Technical Reports Server (NTRS)

    Perez-De-tejada, H.; Intriligator, D. S.; Scarf, F. L.

    1985-01-01

    A study of the angular spread of plasma fluxes detected in the Venus ionosheath is presented. It is shown that in the inner regions of the ionosheath, where the flux intensity is severely decreased with respect to solar wind values, the width of the azimuthal distribution of the local plasma is comparable to, or even larger than, that of the stronger fluxes measured in the outer ionospheath. The observed variation of the angular width suggests the existence of a source of heating near the ionopause but is not consistent with the overall cooling that would be expected if mass loading and charge exchange collisions were solely responsible for the interaction process at that boundary. Dissipative phenomene associated with local plasma turbulence processes seem to be required to account for the broad angular distributions seen near the ionopause.

  19. Plasma measurements of the Pioneer Venus Orbiter in the Venus ionosheath - Evidence for plasma heating near the ionopause

    NASA Astrophysics Data System (ADS)

    Perez-de-Tejada, H.; Intriligator, D. S.; Scarf, F. L.

    1985-02-01

    A study of the angular spread of plasma fluxes detected in the Venus ionosheath is presented. It is shown that in the inner regions of the ionosheath, where the flux intensity is severely decreased with respect to solar wind values, the width of the azimuthal distribution of the local plasma is comparable to, or even larger than, that of the stronger fluxes measured in the outer ionosheath. The observed variation of the angular width suggests the existence of a source of heating near the ionopause but is not consistent with the overall cooling that would be expected if mass loading and charge exchange collisions were solely responsible for the interaction process at that boundary. Dissipative phenomena associated with local plasma turbulent processes seem to be required to account for the broad angular distributions seen near the ionopause.

  20. Observation of spontaneous toroidal rotation inversion in Ohmically heated Tokamak plasmas.

    PubMed

    Bortolon, A; Duval, B P; Pochelon, A; Scarabosio, A

    2006-12-01

    Bulk plasma toroidal rotation is observed to invert spontaneously from counter to cocurrent direction in TCV (Tokamak à Configuration Variable) Ohmically heated discharges, in low confinement mode, without momentum input. The inversion occurs in high current discharges, when the plasma electron density exceeds a well-defined threshold. The transition between the two rotational regimes has been studied by means of density ramps. The results provide evidence of a change of the balance of nondiffusive momentum fluxes in the core of a plasma without an external drive. PMID:17280210

  1. Generation of plasma rotation by ion cyclotron resonance heating in tokamaks

    SciTech Connect

    Chang, C.S.; Phillips, C.K.; White, R.; Zweben, S.; Bonoli, P.T.; Rice, J.E.; Greenwald, M.J.; deGrassie, J.

    1999-05-01

    A physical mechanism for generation of a plasma rotation and radial electric field by ion cyclotron resonance heating (ICRH) is presented in a tokamak geometry. By breaking the omnigenity of resonant ion orbits, ICRH can induce a nonambipolar minor-radial transport of resonant ions. This yields a radial charge separation, a modification to radial electric field E{sub r}, and the generation of plasma rotation. It is estimated that the ICRH fast-wave power available in the present-day tokamak experiments can be large enough to give a significant modification to plasma rotation. {copyright} {ital 1999 American Institute of Physics.}

  2. Grazing incidence technique to obtain spatially resolved spectra from laser heated plasmas

    NASA Technical Reports Server (NTRS)

    Behring, W. E.; Underwood, J. H.; Brown, C. M.; Feldman, U.; Seely, John F.

    1988-01-01

    An experimental method is described in which a grazing incidence spectrograph is used to obtain spatially resolved spectra of laser heated plasmas in the 6-370-A region. In the experiment, small target spheres were irradiated by tightly focused laser beams. A tilted grazing incidence elliptical mirror placed 1.3 m from the target focuses the plasma radiation on the spectrograph slit at a distance of 0.7 m producing a useful degree of spatial resolution in the recorded spectral lines. The spectrum from a copper target is presented together with an X-ray pinhole camera image of the plasma.

  3. Dissipative structures in a plasma with volume heat evolution

    SciTech Connect

    Pavlov, G.A.; Shiryaev, A.A.

    1983-11-01

    We analyzed the system of parabolic equations with a nonlinear and nondiagonal transport-coefficient matrix and with a linear vector-function source. This system of equations corresponds, for example, to an interaction of multicomponent diffusion processes with the volume heat evolution in the cavity of a gas-phase nuclear reactor, a topic which has not been studied previously. This reactor holds promise for the development of power plants. (AIP)

  4. Anomalous inverse bremsstrahlung heating of laser-driven plasmas

    NASA Astrophysics Data System (ADS)

    Kundu, Mrityunjay

    2016-05-01

    Absorption of laser light in plasma via electron-ion collision (inverse bremsstrahlung) is known to decrease with the laser intensity as I 0 -3/2 or with the electron temperature as T e -3/2 where Coulomb logarithm ln Λ = 0.5ln(1 + k 2 min/k 2 max) in the expression of electron-ion collision frequency v ei is assumed to be independent of ponderomotive velocity v 0 = E0/ω which is unjustified. Here k -1 min = v th/max(ω, ω p), and k -1 max = Z/v 2 th are maximum and minimum cut-off distances of the colliding electron from the ion, v th = √T e is its thermal velocity, ω, ω p are laser and plasma frequency. Earlier with a total velocity v = (v 2 0 + v 2 th)1/2 dependent ln Λ(v) it was reported that v ei and corresponding fractional laser absorption (α) initially increases with increasing intensity, reaches a maximum value, and then fall according to the conventional I 0 -3/2 scaling. This anomalous increase in v ei and α may be objected due to an artifact introduced in ln Λ(v) through k-1 min ∝ v. Here we show similar anomalous increase of v ei and α versus I 0 (in the low temperature and under-dense density regime) with quantum and classical kinetic models of v ei without using ln Λ, but a proper choice of the total velocity dependent inverse cut-off length kmax -1 ∝ v 2 (in classical case) or kmax ∝ v (in quantum case). For a given I 0 < 5 × 1014Wcm-2, v ei versus T e also exhibits so far unnoticed identical anomalous increase as v ei versus Io, even if the conventional k max ∝ v2 th, or k max ∝ v th is chosen. However, for higher T e > 15 eV, anomalous growth of vei and a disappear. The total velocity dependent k max in kinetic models, as proposed here, may explain anomalous increase of a with I 0 measured in some earlier laser-plasma experiments. This work may be important to understand collisional absorption in the under-dense pre-plasma region due to low intensity pre-pulses and amplified spontaneous emission (ASE) pedestal in the

  5. Solar wind heavy ions from flare-heated coronal plasma

    NASA Technical Reports Server (NTRS)

    Bame, S. J.; Asbridge, J. R.; Feldman, W. C.; Fenimore, E. E.; Gosling, J. T.

    1979-01-01

    Information concerning the coronal expansion is carried by solar-wind heavy ions. Distinctly different energy-per-charge ion spectra are found in two classes of solar wind having the low kinetic temperatures necessary for E/q resolution of the ion species. Heavy-ion spectra which can be resolved are most frequently observed in the low-speed interstream (IS) plasma found between high speed streams; the streams are thought to originate from coronal holes. Although the sources of the IS plasma are uncertain, the heavy-ion spectra found there contain identifiable peaks of O, Si, and Fe ions. Such spectra indicate that the IS ionization state of O is established in coronal gas at a temperature of approximately 1.6 million K, while that of Fe is frozen in farther out at about 1.5 million K. On occasion anomalous spectra are found outside IS flows in solar wind with abnormally depressed local kinetic temperatures. The anomalous spectra contain Fe(16+) ions, not usually found in IS flows, and the derived coronal freezing-in temperatures are significantly higher. The coronal sources of some of these ionizationally hot flows are identified as solar flares.

  6. Plasma heating, electric fields and plasma flow by electron beam ionospheric injection

    NASA Technical Reports Server (NTRS)

    Winckler, J. R.; Erickson, K. N.

    1990-01-01

    The electric fields and the floating potentials of a Plasma Diagnostics Payload (PDP) located near a powerful electron beam injected from a large sounding rocket into the auroral zone ionosphere have been studied. As the PDP drifted away from the beam laterally, it surveyed a region of hot plasma extending nearly to 60 m radius. Large polarization electric fields transverse to B were imbedded in this hot plasma, which displayed large ELF wave variations and also an average pattern which has led to a model of the plasma flow about the negative line potential of the beam resembling a hydrodynamic vortex in a uniform flow field. Most of the present results are derived from the ECHO 6 sounding rocket mission.

  7. Plasma heating, plasma flow and wave production around an electron beam injected into the ionosphere

    NASA Technical Reports Server (NTRS)

    Winckler, J. R.; Erickson, K. N.

    1986-01-01

    A brief historical summary of the Minnesota ECHO series and other relevant electron beam experiments is given. The primary purpose of the ECHO experiments is the use of conjugate echoes as probes of the magnetosphere, but beam-plasma and wave studies were also made. The measurement of quasi-dc electric fields and ion streaming during the ECHO 6 experiment has given a pattern for the plasma flow in the hot plasma region extending to 60m radius about the ECHO 6 electron beam. The sheath and potential well caused by ion orbits is discussed with the aid of a model which fits the observations. ELF wave production in the plasma sheath around the beam is briefly discussed. The new ECHO 7 mission to be launched from the Poker Flat range in November 1987 is described.

  8. ECE diagnostic of high temperature ECRH heated plasmas on FTU

    SciTech Connect

    Zerbini, M; Buratti, P; Tudisco, O; Giruzzi, G; Bruschi, A; Cirant, S; Granucci, G; Simonetto, A; Sozzi, C; Gandini, F; Pacella, D; Fournier, K B; Finkenthal, M

    2000-01-31

    The Electron Cyclotron Emission (ECE) diagnostic on FTU tokamak is routinely performed with a Michelson interferometer with spectral range extending up to 1300 GHz. The diagnostic allowed accurate electron temperature measurements during the recent 140 Ghz Electron Cyclotron Resonance Heating (ECRH) experiments on FTU. Very accurate measurements have been performed on a wide range of electron temperatures and profile peaking. The ECE measurements have been compared with Thomson Scattering and with observations of X-ray spectra from highly stripped molybdenum ions. The suprathermal emission in these conditions has been studied.

  9. Heat treatment for endocrinological investigations on plasma positive for human immunodeficiency virus (HIV).

    PubMed Central

    Hancock, M R; Knapp, M L; Ghany, H C; Mayne, P D

    1987-01-01

    The effects of heat treatment of serum samples on the hormone analyses used in this laboratory were studied. Total T4, testosterone, progesterone, and growth hormone were not systematically affected by heat treatment over the whole range of analyte concentrations studied; for thyroid stimulating hormone, no effect was noted on serum samples with concentrations of less than 10 mU/l. Significant changes occurred in total T3, cortisol, follicle stimulating hormone, luteinizing hormone, and prolactin. It is suggested that with appropriate preliminary study, heat treated plasma samples may be used in endocrinological investigations without adversely affecting the diagnostic validity of the results. PMID:3108328

  10. Absolute stability in a collisionless electron-heat-conducting plasma in strong magnetic fields

    NASA Astrophysics Data System (ADS)

    de la Torre, A.; Duhau, S.

    1989-02-01

    The dispersion relation obtained from a linear analysis of the hydrodynamic system of equations of Duhau is used to study the behaviour of the fast and slow magnetosonic and entropy modes in an electron-heat-flux-conducting plasma. The evolution of the hydrodynamic modes different from the Alfvén mode are studied as the electron heat flux is increased from zero as well as around the borders of overstable regions, for any anisotropy condition of the ions. The development of the domains of mirror and electron-heat-flux overstabilities are established and the regions of absolute stability are shown

  11. Literature review of arc/plasma, combustion, and joule-heated melter vitrification systems

    SciTech Connect

    Freeman, C.J.; Abrigo, G.P.; Shafer, P.J.; Merrill, R.A.

    1995-07-01

    This report provides reviews of papers and reports for three basic categories of melters: arc/plasma-heated melters, combustion-heated melters, and joule-heated melters. The literature reviewed here represents those publications which may lend insight to phase I testing of low-level waste vitrification being performed at the Hanford Site in FY 1995. For each melter category, information from those papers and reports containing enough information to determine steady-state mass balance data is tabulated at the end of each section. The tables show the composition of the feed processed, the off-gas measured via decontamination factors, gross energy consumptions, and processing rates, among other data.

  12. Fast frequency-step-tunable gyrotrons for plasma heating and fusion diagnostics

    SciTech Connect

    Dumbrajs, O.; Heikkinen, J.

    1994-11-01

    Usefulness of frequency tunable sources for plasma heating and fusion diagnostics is studied. Applicability of fast frequency-step-tunable gyrotrons for these purposes is examined. A gyrotron based on a coaxial cavity with impedance rod is considered as an example.

  13. Extreme degree of ionization in homogenous micro-capillary plasma columns heated by ultrafast current pulses.

    PubMed

    Avaria, G; Grisham, M; Li, J; Tomasel, F G; Shlyaptsev, V N; Busquet, M; Woolston, M; Rocca, J J

    2015-03-01

    Homogeneous plasma columns with ionization levels typical of megaampere discharges are created by rapidly heating gas-filled 520-μm-diameter channels with nanosecond rise time current pulses of 40 kA. Current densities of up to 0.3  GA cm^{-2} greatly increase Joule heating with respect to conventional capillary discharge Z pinches, reaching unprecedented degrees of ionization for a high-Z plasma column heated by a current pulse of remarkably low amplitude. Dense xenon plasmas are ionized to Xe^{28+}, while xenon impurities in hydrogen discharges reach Xe^{30+}. The unique characteristics of these hot, ∼300:1 length-to-diameter aspect ratio plasmas allow the observation of unexpected spectroscopic phenomena. Axial spectra show the unusual dominance of the intercombination line over the resonance line of He-like Al by nearly an order of magnitude, caused by differences in opacities in the axial and radial directions. These plasma columns could enable the development of sub-10-nm x-ray lasers. PMID:25793819

  14. Gyrokinetic simulations of momentum transport and fluctuation spectra for ICRF-heated L-Mode plasmas

    NASA Astrophysics Data System (ADS)

    Sierchio, J. M.; White, A. E.; Howard, N. T.; Sung, C.; Ennever, P.; Porkolab, M.; Candy, J.

    2014-10-01

    We examine ICRF-heated L-mode plasmas in Alcator C-Mod, with differing momentum transport (hollow vs. peaked radial profiles of intrinsic toroidal rotation) but similar heat and particle transport. Nonlinear gyrokinetic simulations of heat and particle transport with GYRO [Candy and Waltz, J. Comp. Phys. 186, 545 (2003)] have previously been compared with these experiments [White et al., Phys. Plasmas 20, 056106 (2013); Howard et al. PPCF submitted (2014)] as part of an effort to validate the gyrokinetic model for core turbulent transport in C-Mod plasmas. To further test the model for these plasmas, predicted core turbulence characteristics such as fluctuation spectra will be compared with experiment. Using synthetic diagnostics for the CECE, reflectometry, and PCI systems at C-Mod, synthetic spectra and, when applicable, fluctuation amplitudes, are generated. We compare these generated results with fluctuation measurements from the experiment. We also report the momentum transport results from simulations of these plasmas and compare them to experiment. Supported by USDoE award DE-FC02-99ER54512.

  15. Extreme Degree of Ionization in Homogenous Micro-Capillary Plasma Columns Heated by Ultrafast Current Pulses

    NASA Astrophysics Data System (ADS)

    Avaria, G.; Grisham, M.; Li, J.; Tomasel, F. G.; Shlyaptsev, V. N.; Busquet, M.; Woolston, M.; Rocca, J. J.

    2015-03-01

    Homogeneous plasma columns with ionization levels typical of megaampere discharges are created by rapidly heating gas-filled 520 -μ m -diameter channels with nanosecond rise time current pulses of 40 kA. Current densities of up to 0.3 GA cm-2 greatly increase Joule heating with respect to conventional capillary discharge Z pinches, reaching unprecedented degrees of ionization for a high-Z plasma column heated by a current pulse of remarkably low amplitude. Dense xenon plasmas are ionized to Xe28 + , while xenon impurities in hydrogen discharges reach Xe30 + . The unique characteristics of these hot, ˜300 :1 length-to-diameter aspect ratio plasmas allow the observation of unexpected spectroscopic phenomena. Axial spectra show the unusual dominance of the intercombination line over the resonance line of He-like Al by nearly an order of magnitude, caused by differences in opacities in the axial and radial directions. These plasma columns could enable the development of sub-10-nm x-ray lasers.

  16. Development of High Power Vacuum Tubes for Accelerators and Plasma Heating

    NASA Astrophysics Data System (ADS)

    Srivastava, Vishnu

    2012-11-01

    High pulsed power magnetrons and klystrons for medical and industrial accelerators, and high CW power klystrons and gyrotrons for plasma heating in tokamak, are being developed at CEERI. S-band 2.0MW pulsed tunable magnetrons of centre frequency 2856MHz and 2998 MHz were developed, and S-band 2.6MW pulsed tunable magnetron is being developed for medical LINAC, and 3MW pulsed tunable magnetron is being developed for industrial accelerator. S-band (2856MHz), 5MW pulsed klystron was developed for particle accelerator, and S-band 6MW pulsed klystron is under development for 10MeV industrial accelerator. 350MHz, 100kW (CW) klystron is being developed for proton accelerator, and C-band 250kW (CW) klystron is being developed for plasma heating. 42GHz, 200kW (CW/Long pulse) gyrotron is under development for plasma heating. Plasma filled tubes are also being developed for switching. 25kV/1kA and 40kV/3kA thyratrons were developed for high voltage high current switching in pulse modulators for magnetrons and klystrons. 25kV/3kA Pseudospark switch of current rise time of 1kA/|a-sec and pulse repetition rate of 500Hz is being developed. Plasma assisted high power microwave device is also being investigated.

  17. Simulation of High Power ICRF Wave Heating in the ITER Burning Plasma

    NASA Astrophysics Data System (ADS)

    Jaeger, E. F.; Berry, L. A.; Barrett, R. F.; D'Azevedo, E. F.

    2007-11-01

    ITER relies on Ion-cyclotron Radio Frequency (ICRF) power to heat the plasma to fusion temperatures. To heat effectively, the waves must couple efficiently to the core plasma. Recent simulations using AORSA [1] on the 120 TF Cray XT-4 (Jaguar) at ORNL show that the waves propagate radially inward and are rapidly absorbed with little heating of the plasma edge. AORSA has achieved 87.5 trillion calculations per second (87.5 teraflops) on Jaguar, which is 73 percent of the system's theoretical peak. Three dimensional visualizations show ``hot spots'' near the antenna surface where the wave amplitude is high. AORSA simulations are also being used to study how to best use ICRF to drive plasma currents for optimizing ITER performance and pulse length. Results for Scenario 4 show a maximum current of 0.54 MA for 20 MW of power at 57 MHz. [1] E.F. Jaeger, L.A. Berry, E. D'Azevedo, et al., Phys. Plasmas. 8, 1573 (2001).

  18. HHFW Heating and Current Drive Studies of NSTX H-Mode Plasmas

    SciTech Connect

    Taylor, G.; Hosea, J. C.; LeBlanc, B. P.; Phillips, C. K.; Valeo, E. J.; Wilson, J. R.; Bonoli, P. T.; Wright, J. C.; Green, D. L.; Jaeger, E. F.; Maingi, R.; Ryan, P. M.; Harvey, R. W.

    2011-12-23

    30 MHz high-harmonic fast wave (HHFW) heating and current drive are being developed to assist fully non-inductive plasma current (I{sub p}) ramp-up in NSTX. The initial approach to achieving this goal has been to heat I{sub p} = 300 kA inductive plasmas with current drive antenna phasing in order to generate an HHFW H-mode with significant bootstrap and RF-driven current. Recent experiments, using only 1.4 MW of RF power (P{sub RF}), achieved a non-inductive current fraction, f{sub NI}{approx}0.65. Improved antenna conditioning resulted in the generation of I{sub p} = 650 kA HHFW H-mode plasmas, with f{sub NI}{approx}0.35, when P{sub RF}{>=}2.5 MW. These plasmas have little or no edge localized mode (ELM) activity during HHFW heating, a substantial increase in stored energy and a sustained central electron temperature of 5-6 keV. Another focus of NSTX HHFW research is to heat an H-mode generated by 90 keV neutral beam injection (NBI). Improved HHFW coupling to NBI-generated H-modes has resulted in a broad increase in electron temperature profile when HHFW heating is applied. Analysis of a closely matched pair of NBI and HHFW+NBI H-mode plasmas revealed that about half of the antenna power is deposited inside the last closed flux surface (LCFS). Of the power damped inside the LCFS about two-thirds is absorbed directly by electrons and one-third accelerates fast-ions that are mostly promptly lost from the plasma. At longer toroidal launch wavelengths, HHFW+NBI H-mode plasmas can have an RF power flow to the divertor outside the LCFS that significantly reduces RF power deposition to the core. ELMs can also reduce RF power deposition to the core and increase power deposition to the edge. Recent full wave modeling of NSTX HHFW+NBI H-mode plasmas, with the model extended to the vessel wall, predicts a coaxial standing mode between the LCFS and the wall that can have large amplitudes at longer launch wavelengths. These simulation results qualitatively agree with HHFW

  19. HHFW Heating and Current Drive Studies of NSTX H-Mode Plasmas

    SciTech Connect

    G. Taylor, P.T. Bonoli, D.L. Green, R.W. Harvey, J.C. Hosea, E.F. Jaeger, B.P. LeBlanc, R. Maingi, C.K. Phillips, P.M. Ryan, E.J. Valeo, J.R. Wilson, J.C. Wright, and the NSTX Team

    2011-06-08

    30 MHz high-harmonic fast wave (HHFW) heating and current drive are being developed to assist fully non-inductive plasma current (I{sub p}) ramp-up in NSTX. The initial approach to achieving this goal has been to heat I{sub p} = 300 kA inductive plasmas with current drive antenna phasing in order to generate an HHFW H-mode with significant bootstrap and RF-driven current. Recent experiments, using only 1.4 MW of RF power (P{sub RF}), achieved a noninductive current fraction, f{sub NI} {approx} 0.65. Improved antenna conditioning resulted in the generation of I{sub p} = 650 kA HHFW H-mode plasmas, with f{sub NI} {approx} 0.35, when P{sub RF} {ge} 2.5 MW. These plasmas have little or no edge localized mode (ELM) activity during HHFW heating, a substantial increase in stored energy and a sustained central electron temperature of 5-6 keV. Another focus of NSTX HHFW research is to heat an H-mode generated by 90 keV neutral beam injection (NBI). Improved HHFW coupling to NBI-generated H-modes has resulted in a broad increase in electron temperature profile when HHFW heating is applied. Analysis of a closely matched pair of NBI and HHFW+NBI H-mode plasmas revealed that about half of the antenna power is deposited inside the last closed flux surface (LCFS). Of the power damped inside the LCFS about two-thirds is absorbed directly by electrons and one-third accelerates fast-ions that are mostly promptly lost from the plasma. At longer toroidal launch wavelengths, HHFW+NBI H-mode plasmas can have an RF power flow to the divertor outside the LCFS that significantly reduces RF power deposition to the core. ELMs can also reduce RF power deposition to the core and increase power deposition to the edge. Recent full wave modeling of NSTX HHFW+NBI H-mode plasmas, with the model extended to the vessel wall, predicts a coaxial standing mode between the LCFS and the wall that can have large amplitudes at longer launch wavelengths. These simulation results qualitatively agree with HHFW

  20. Heating efficiency evaluation with mimicking plasma conditions of integrated fast-ignition experiment.

    PubMed

    Fujioka, Shinsuke; Johzaki, Tomoyuki; Arikawa, Yasunobu; Zhang, Zhe; Morace, Alessio; Ikenouchi, Takahito; Ozaki, Tetsuo; Nagai, Takahiro; Abe, Yuki; Kojima, Sadaoki; Sakata, Shohei; Inoue, Hiroaki; Utsugi, Masaru; Hattori, Shoji; Hosoda, Tatsuya; Lee, Seung Ho; Shigemori, Keisuke; Hironaka, Youichiro; Sunahara, Atsushi; Sakagami, Hitoshi; Mima, Kunioki; Fujimoto, Yasushi; Yamanoi, Kohei; Norimatsu, Takayoshi; Tokita, Shigeki; Nakata, Yoshiki; Kawanaka, Junji; Jitsuno, Takahisa; Miyanaga, Noriaki; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Nagatomo, Hideo; Azechi, Hiroshi

    2015-06-01

    A series of experiments were carried out to evaluate the energy-coupling efficiency from heating laser to a fuel core in the fast-ignition scheme of laser-driven inertial confinement fusion. Although the efficiency is determined by a wide variety of complex physics, from intense laser plasma interactions to the properties of high-energy density plasmas and the transport of relativistic electron beams (REB), here we simplify the physics by breaking down the efficiency into three measurable parameters: (i) energy conversion ratio from laser to REB, (ii) probability of collision between the REB and the fusion fuel core, and (iii) fraction of energy deposited in the fuel core from the REB. These three parameters were measured with the newly developed experimental platform designed for mimicking the plasma conditions of a realistic integrated fast-ignition experiment. The experimental results indicate that the high-energy tail of REB must be suppressed to heat the fuel core efficiently. PMID:26172803

  1. The effect of quantum correction on plasma electron heating in ultraviolet laser interaction

    SciTech Connect

    Zare, S.; Sadighi-Bonabi, R. Anvari, A.; Yazdani, E.; Hora, H.

    2015-04-14

    The interaction of the sub-picosecond UV laser in sub-relativistic intensities with deuterium is investigated. At high plasma temperatures, based on the quantum correction in the collision frequency, the electron heating and the ion block generation in plasma are studied. It is found that due to the quantum correction, the electron heating increases considerably and the electron temperature uniformly reaches up to the maximum value of 4.91 × 10{sup 7 }K. Considering the quantum correction, the electron temperature at the laser initial coupling stage is improved more than 66.55% of the amount achieved in the classical model. As a consequence, by the modified collision frequency, the ion block is accelerated quicker with higher maximum velocity in comparison with the one by the classical collision frequency. This study proves the necessity of considering a quantum mechanical correction in the collision frequency at high plasma temperatures.

  2. Generation of high charge state platinum ions on vacuum arc plasma heated by gyrotron radiation.

    PubMed

    Yushkov, G Yu; Vodopyanov, A V; Nikolaev, A G; Izotov, I V; Savkin, K P; Golubev, S V; Oks, E M

    2014-02-01

    The hybrid high charge metal ion source based on vacuum arc plasma heated by gyrotron radiation into simple magnetic trap has been developed. Two types of magnetic traps were used: a mirror configuration and a cusp one with inherent "minimum-B" structure. Pulsed high power (>100 kW) gyrotrons with frequency 37.5 GHz and 75 GHz were used for heating the vacuum arc plasma injected into the traps. Two different ways were used for injecting the metal plasma-axial injection by a miniature arc source located on-axis near the microwave window, and simultaneous radial injection by a number of sources mounted radially at the midplane of the traps. This article represents all data gathered for platinum ions, thus making comparison of the experimental results obtained with different traps and injections convenient and accurate. PMID:24593607

  3. Plasma Heating in Highly Excited GaN/AlGaN Multiple Quantum Wells

    SciTech Connect

    Botchkarev, A; Chow, W W; Jiang, H X; Lin, J Y; Mair, R; Morkoc, H; Zeng, K C

    1998-10-09

    Plasma Heating in Highly Excited GaN/AIGaN Multiple Quantum @@lvEu Wells w f + 1998 %p, K. C. Zeng, R. Mair, J. Y. Liz and H. X. Jiang a) ` fabrication and understanding of MQW lasers [2-5]. For the design of these lasers, one on RT optical studies. Our results revealed that in the GaN/AIGaN MQWS, plasma heating strongly effects the carrier distribution between the confined and unconfined band-to-band and fke excitonic transitions [7]. In the MQW sample under low the unconfined states as determined from the band structure. sample under high Lxc, we varied the excitation intensity by one order of magnitude from 0.110 to IO. The carrier density is estimated to be about N=1012/cm2 (at UC= 0.1 Io) to 1013/cm2 (at 1=== l.). We plotted the PL spectra for four representative excitation fimction of injected carrier density N (open squares). The ratio starts at a value of about 18% for N=1012/cm2 (& = O. lb), and reaches a value over 64 `XO for N=1013/cm2 (& = regions is a loss to optical gain. The carrier density is ve~ high in our experiment and an electron-hole plasma (EHP) state is expected. Because the carrier transfer process plasma temperature. The laser pump energy is about 4.3 eV, which is far above the energy band gap of the sample studied here. This may result in a hot carrier population carrier densities and plasma temperatures. Using a phenomenological expression based The calculated ratio of carriers in the unconfked to the confined states (Ima~ kf) as a finction of carrier density at different temperatures are plotted in Fig. 3 (solid lines). The figure shows that the experiment results can only be explained by plasma heating of the injected carriers at high & ( TP > TJ. The transparency carrier densities for GaN/AIXGal.XN MQW structures with well thickness from 2 to 4 nm were calculated to be around 1x 1012/cm2 [10]. It is thus obvious from Fig. 3 that under high carrier injection density above the transparency density, the plasma temperature, TP, is no

  4. Ballooning Instability: A Possible Mechanism for Impulsive Heating of Plasma Trapped in a Loop

    NASA Astrophysics Data System (ADS)

    Shibasaki, K.

    2015-12-01

    Plasma confined in curved magnetic field are unstable when the plasma beta (= gas pressure / magnetic pressure) exceeds a critical value determined mainly by the loop geometry (~ loop thickness / curvature radius). In TOKAMAK (one type of fusion experiment device), sudden disruption of confined plasma are observed when plasma beta is high and is called high-beta disruption. The main cause of the disruption is ballooning instability (or localized interchange instability). This instability can happen also in the solar atmosphere when conditions are satisfied. Not only high gas pressure but also plasma flow along curved magnetic field triggers ballooning instability. The most probable location of the instability is around the loop top where the magnetic field is the weakest. Impulsive heating of confined plasma and particle acceleration can be expected by discharge process of the space charge which is created by drift motion of plasma particles perpendicular to the magnetic field. Associated with disruption, shock waves and turbulences will be generated due to sudden expansion of plasma. Recent high-resolution, high-cadence and multiple wavelength (visible-UV-EUV) observations by SDO show many of these events.

  5. Heat loads to divertor nearby components from secondary radiation evolved during plasma instabilities

    NASA Astrophysics Data System (ADS)

    Sizyuk, V.; Hassanein, A.

    2015-01-01

    A fundamental issue in tokamak operation related to power exhaust during plasma instabilities is the understanding of heat and particle transport from the core plasma into the scrape-off layer and to plasma-facing materials. During abnormal and disruptive operation in tokamaks, radiation transport processes play a critical role in divertor/edge-generated plasma dynamics and are very important in determining overall lifetimes of the divertor and nearby components. This is equivalent to or greater than the effect of the direct impact of escaped core plasma on the divertor plate. We have developed and implemented comprehensive enhanced physical and numerical models in the upgraded HEIGHTS package for simulating detailed photon and particle transport in the evolved edge plasma during various instabilities. The paper describes details of a newly developed 3D Monte Carlo radiation transport model, including optimization methods of generated plasma opacities in the full range of expected photon spectra. Response of the ITER divertor's nearby surfaces due to radiation from the divertor-developed plasma was simulated by using actual full 3D reactor design and magnetic configurations. We analyzed in detail the radiation emission spectra and compared the emission of both carbon and tungsten as divertor plate materials. The integrated 3D simulation predicted unexpectedly high damage risk to the open stainless steel legs of the dome structure in the current ITER design from the intense radiation during a disruption on the tungsten divertor plate.

  6. Heating and acceleration of solar wind ions by turbulent wave spectrum in inhomogeneous expanding plasma

    NASA Astrophysics Data System (ADS)

    Ofman, Leon; Ozak, Nataly; Viñas, Adolfo F.

    2016-03-01

    Near the Sun (< 10Rs) the acceleration, heating, and propagation of the solar wind are likely affected by the background inhomogeneities of the magnetized plasma. The heating and the acceleration of the solar wind ions by turbulent wave spectrum in inhomogeneous plasma is studied using a 2.5D hybrid model. The hybrid model describes the kinetics of the ions, while the electrons are modeled as massless neutralizing fluid in an expanding box approach. Turbulent magnetic fluctuations dominated by power-law frequency spectra, which are evident from in-situ as well as remote sensing measurements, are used in our models. The effects of background density inhomogeneity across the magnetic field on the resonant ion heating are studied. The effect of super-Alfvénic ion drift on the ion heating is investigated. It is found that the turbulent wave spectrum of initially parallel propagating waves cascades to oblique modes, and leads to enhanced resonant ion heating due to the inhomogeneity. The acceleration of the solar wind ions is achieved by the parametric instability of large amplitude waves in the spectrum, and is also affected by the inhomogeneity. The results of the study provide the ion temperature anisotropy and drift velocity temporal evolution due to relaxation of the instability. The non-Maxwellian velocity distribution functions (VDFs) of the ions are modeled in the inhomogeneous solar wind plasma in the acceleration region close to the Sun.

  7. Initial Operation of the Miniaturized Inductively Heated Plasma Generator IPG6

    NASA Astrophysics Data System (ADS)

    Dropmann, Michael; Herdrich, Georg; Laufer, Rene; Koch, Helmut; Gomringer, Chris; Cook, Mike; Schmoke, Jimmy; Matthews, Lorin; Hyde, Truell

    2012-10-01

    In close collaboration between the Center for Astrophysics, Space Physics and Engineering Research (CASPER) at Baylor University, Texas, and the Institute of Space Systems (IRS) at the University of Stuttgart, Germany, two plasma wind tunnel facilities of similar type have been established using the inductively heated plasma source IPG6 which is based on proven IRS designs. The facility at Baylor University (IPG6-B) works at a frequency of 13.56 MHz and a maximum power of 15 kW. A vacuum pump of 160m^3/h in combination with a butterfly valve allows pressure control in a wide range. First experiments have been conducted with Air, O2 and N2 as working gases and volumetric flow rates of up to 14 L/min at pressures of a few 100 Pa, although pressures below 1 Pa are achievable at lower flow rates. The maximum tested electric power so far was 8 kW. Plasma powers and total pressures in the plasma jet have been obtained. In the near future the set up of additional diagnostics, the use of other gases (i.e. H2, He), and the integration of a dust particle accelerator are planned. The intended fields of research are basic investigation in thermo-chemistry and plasma radiation, space plasma environments and high heat fluxes e.g. in fusion devices or during atmospheric entry of spacecraft.

  8. High current multicharged metal ion source using high power gyrotron heating of vacuum arc plasma.

    PubMed

    Vodopyanov, A V; Golubev, S V; Khizhnyak, V I; Mansfeld, D A; Nikolaev, A G; Oks, E M; Savkin, K P; Vizir, A V; Yushkov, G Yu

    2008-02-01

    A high current, multi charged, metal ion source using electron heating of vacuum arc plasma by high power gyrotron radiation has been developed. The plasma is confined in a simple mirror trap with peak magnetic field in the plug up to 2.5 T, mirror ratio of 3-5, and length variable from 15 to 20 cm. Plasma formed by a cathodic vacuum arc is injected into the trap either (i) axially using a compact vacuum arc plasma gun located on axis outside the mirror trap region or (ii) radially using four plasma guns surrounding the trap at midplane. Microwave heating of the mirror-confined, vacuum arc plasma is accomplished by gyrotron microwave radiation of frequency 75 GHz, power up to 200 kW, and pulse duration up to 150 micros, leading to additional stripping of metal ions by electron impact. Pulsed beams of platinum ions with charge state up to 10+, a mean charge state over 6+, and total (all charge states) beam current of a few hundred milliamperes have been formed. PMID:18315170

  9. High current multicharged metal ion source using high power gyrotron heating of vacuum arc plasma

    SciTech Connect

    Vodopyanov, A. V.; Golubev, S. V.; Khizhnyak, V. I.; Mansfeld, D. A.; Nikolaev, A. G.; Oks, E. M.; Savkin, K. P.; Vizir, A. V.; Yushkov, G. Yu.

    2008-02-15

    A high current, multi charged, metal ion source using electron heating of vacuum arc plasma by high power gyrotron radiation has been developed. The plasma is confined in a simple mirror trap with peak magnetic field in the plug up to 2.5 T, mirror ratio of 3-5, and length variable from 15 to 20 cm. Plasma formed by a cathodic vacuum arc is injected into the trap either (i) axially using a compact vacuum arc plasma gun located on axis outside the mirror trap region or (ii) radially using four plasma guns surrounding the trap at midplane. Microwave heating of the mirror-confined, vacuum arc plasma is accomplished by gyrotron microwave radiation of frequency 75 GHz, power up to 200 kW, and pulse duration up to 150 {mu}s, leading to additional stripping of metal ions by electron impact. Pulsed beams of platinum ions with charge state up to 10+, a mean charge state over 6+, and total (all charge states) beam current of a few hundred milliamperes have been formed.

  10. Modeling the heating and atomic kinetics of a photoionized neon plasma experiment

    NASA Astrophysics Data System (ADS)

    Lockard, Tom E.

    Motivated by gas cell photoionized plasma experiments performed by our group at the Z facility of Sandia National Laboratories, we discuss in this dissertation a modeling study of the heating and ionization of the plasma for conditions characteristic of these experiments. Photoionized plasmas are non-equilibrium systems driven by a broadband x-ray radiation flux. They are commonly found in astrophysics but rarely seen in the laboratory. Several modeling tools have been employed: (1) a view-factor computer code constrained with side x-ray power and gated monochromatic image measurements of the z-pinch radiation, to model the time-history of the photon-energy resolved x-ray flux driving the photoionized plasma, (2) a Boltzmann self-consistent electron and atomic kinetics model to simulate the electron distribution function and configuration-averaged atomic kinetics, (3) a radiation-hydrodynamics code with inline non-equilibrium atomic kinetics to perform a comprehensive numerical simulation of the experiment and plasma heating, and (4) steady-state and time-dependent collisional-radiative atomic kinetics calculations with fine-structure energy level description to assess transient effects in the ionization and charge state distribution of the plasma. The results indicate that the photon-energy resolved x-ray flux impinging on the front window of the gas cell is very well approximated by a linear combination of three geometrically-diluted Planckian distributions. Knowledge of the spectral details of the x-ray drive turned out to be important for the heating and ionization of the plasma. The free electrons in the plasma thermalize quickly relative to the timescales associated with the time-history of the x-ray drive and the plasma atomic kinetics. Hence, electrons are well described by a Maxwellian energy distribution of a single temperature. This finding is important to support the application of a radiation-hydrodynamic model to simulate the experiment. It is found

  11. MM-wave cyclotron auto-resonance maser for plasma heating

    SciTech Connect

    Ceccuzzi, S.; Ravera, G. L.; Tuccillo, A. A.; Dattoli, G.; Di Palma, E.; Doria, A.; Gallerano, G. P.; Giovenale, E.; Spassovsky, I.; Surrenti, V.; Mirizzi, F.

    2014-02-12

    Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. Heating systems based on the electron cyclotron resonance (ECRH) have been extensively exploited on past and present machines DEMO, and the future reactor will require high frequencies. Therefore, high power (≥1MW) RF sources with output frequency in the 200 - 300 GHz range would be necessary. A promising source is the so called Cyclotron Auto-Resonance Maser (CARM). Preliminary results of the conceptual design of a CARM device for plasma heating, carried out at ENEA-Frascati will be presented together with the planned R and D development.

  12. Fast ion generation and bulk plasma heating with three-ion ICRF scenarios

    SciTech Connect

    Kazakov, Ye. O. Van Eester, D.; Ongena, J.; Lerche, E.; Messiaen, A.

    2015-12-10

    Launching electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is an efficient method of plasma heating, actively employed in most of fusion machines. ICRF has a number of important supplementary applications, including the generation of high-energy ions. In this paper, we discuss a new set of three-ion ICRF scenarios and the prospect of their use as a dedicated tool for fast ion generation in tokamaks and stellarators. A distinct feature of these scenarios is a strong absorption efficiency possible at very low concentrations of resonant minority ions (∼ 1% or even below). Such concentration levels are typical for impurities contaminating fusion plasmas. An alternative ICRF scenario for maximizing the efficiency of bulk D-T ion heating is suggested for JET and ITER tokamaks, which is based on three-ion ICRF heating of intrinsic Beryllium impurities.

  13. MM-wave cyclotron auto-resonance maser for plasma heating

    NASA Astrophysics Data System (ADS)

    Ceccuzzi, S.; Dattoli, G.; Di Palma, E.; Doria, A.; Gallerano, G. P.; Giovenale, E.; Mirizzi, F.; Spassovsky, I.; Ravera, G. L.; Surrenti, V.; Tuccillo, A. A.

    2014-02-01

    Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. Heating systems based on the electron cyclotron resonance (ECRH) have been extensively exploited on past and present machines DEMO, and the future reactor will require high frequencies. Therefore, high power (≥1MW) RF sources with output frequency in the 200 - 300 GHz range would be necessary. A promising source is the so called Cyclotron Auto-Resonance Maser (CARM). Preliminary results of the conceptual design of a CARM device for plasma heating, carried out at ENEA-Frascati will be presented together with the planned R&D development.

  14. Fast ion generation and bulk plasma heating with three-ion ICRF scenarios

    NASA Astrophysics Data System (ADS)

    Kazakov, Ye. O.; Van Eester, D.; Dumont, R.; Ongena, J.; Lerche, E.; Messiaen, A.

    2015-12-01

    Launching electromagnetic waves in the ion cyclotron range of frequencies (ICRF) is an efficient method of plasma heating, actively employed in most of fusion machines. ICRF has a number of important supplementary applications, including the generation of high-energy ions. In this paper, we discuss a new set of three-ion ICRF scenarios and the prospect of their use as a dedicated tool for fast ion generation in tokamaks and stellarators. A distinct feature of these scenarios is a strong absorption efficiency possible at very low concentrations of resonant minority ions (˜ 1% or even below). Such concentration levels are typical for impurities contaminating fusion plasmas. An alternative ICRF scenario for maximizing the efficiency of bulk D-T ion heating is suggested for JET and ITER tokamaks, which is based on three-ion ICRF heating of intrinsic Beryllium impurities.

  15. Comparison of transient electron heat transport in LHD helical and JT-60U tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Inagaki, S.; Takenaga, H.; Ida, K.; Isayama, A.; Tamura, N.; Takizuka, T.; Shimozuma, T.; Kamada, Y.; Kubo, S.; Miura, Y.; Nagayama, Y.; Kawahata, K.; Sudo, S.; Ohkubo, K.; LHD Experimental Group; JT-60 Team

    2006-01-01

    Transient transport experiments are performed in plasmas with and without internal transport barriers (ITB) on LHD and JT-60U. The dependence of χe on the electron temperature, Te, and on the electron temperature gradient, ∇Te, is analysed with an empirical non-linear heat transport model. In plasmas without an ITB, two different types of non-linearity of the electron heat transport are observed from cold/heat pulse propagation: the χe depends on Te and ∇Te in JT-60U, while the ∇Te dependence is weak in LHD. Inside the ITB region, there is none or weak ∇Te dependence both in LHD and JT-60U. Growth of the cold pulse driven by the negative Te dependence of χe is observed inside the ITB region (LHD) and near the boundary of the ITB region (JT-60U).

  16. Observation of heat flux and plasma flow in scrape off layer in QUEST

    NASA Astrophysics Data System (ADS)

    Onchi, T.; Mahira, Y.; Nagaoka, K.; Tashima, S.; Banerjee, S.; Mishra, K.; Idei, H.; Hanada, K.; Nakamura, K.; Fujisawa, A.; Nagashima, Y.; Hasegawa, M.; Matsuoka, K.; Kuzmin, A.; Watanabe, O.; Kawasaki, S.; Nakashima, H.; Higashijima, A.

    2015-08-01

    Thermal probe with double function of thermocouples and Langmuir probe has been developed, and the initial data observed in far-SOL in QUEST is obtained. Heat flux of megawatt per square meters related to energetic electrons and sonic plasma flow in far-SOL have been observed in the current rump-up phase although no high power inductive force like ohmic winding is applied. The heat flux and the flow are suppressed after the current is built up. In the quasi-steady state, plasma current starts and keeps sawtooth-like oscillation with 20 Hz frequency. The heat flux and the flow in far-SOL have clear responses to the oscillation.

  17. Heat transport in a two-dimensional complex (dusty) plasma at melting conditions

    NASA Astrophysics Data System (ADS)

    Nosenko, V.; Ivlev, A. V.; Zhdanov, S.; Morfill, G.; Goree, J.; Piel, A.

    2007-11-01

    The heat transport in a two-dimensional complex (dusty) plasma undergoing a phase transition was studied experimentally. A single layer of highly charged polymer microspheres was suspended in a plasma sheath. In the absence of manipulation, the suspension forms a 2D triangular lattice. To melt this lattice and form a liquid, we used a laser-heating method. Two focused laser beams were moved rapidly around in the monolayer. The kinetic temperature of the particles increased with the laser power applied, and above a threshold a melting transition occurred. We used video microscopy for direct imaging and particle tracking. The spatial profiles of the particle kinetic temperature were calculated. Using the heat transport equation with an additional term to account for the energy dissipation due to the gas drag, we analyzed the temperature profiles to find a thermal conductivity, which did not depend on temperature.

  18. Heating of solar chromosphere by electromagnetic wave absorption in a plasma slab model

    SciTech Connect

    Tsiklauri, D.; Pechhacker, R.

    2011-04-15

    The heating of solar chromospheric internetwork regions by means of the absorption of electromagnetic (EM) waves that originate from the photospheric blackbody radiation is studied in the framework of a plasma slab model. The absorption is provided by the electron-neutral collisions in which electrons oscillate in the EM wave field and electron-neutral collisions damp the EM wave. Given the uncertain nature of the collision cross-section due to the plasma microturbulence, it is shown that for plausible physical parameters, the heating flux produced by the absorption of EM waves in the chromosphere is between 20% and 45% of the chromospheric radiative loss flux requirement. It is also established that there is an optimal value for the collision cross-section, 5x10{sup -18} m{sup 2}, which produces the maximal heating flux of 1990 W m{sup -2}.

  19. Influence of surface conditions on plasma dynamics and electron heating in a radio-frequency driven capacitively coupled oxygen plasma

    NASA Astrophysics Data System (ADS)

    Greb, Arthur; Gibson, Andrew Robert; Niemi, Kari; O'Connell, Deborah; Gans, Timo

    2015-08-01

    The impact of changing surface condition on plasma dynamics and electron heating is investigated by means of numerical simulations, based on a semi-kinetic fluid model approach, and compared with measurements of the nanosecond electron dynamics in the plasma-surface interface region using phase resolved optical emission spectroscopy (PROES). The simulations are conducted in a one-dimensional domain and account for a geometrical asymmetry comparable to the experimental setup of a radio-frequency driven capacitively coupled plasma in a gaseous electronics conference reference cell. A simple reaction scheme is considered, including electrons, \\text{O}2+ positive ions, {{\\text{O}}-} negative ions and {{\\text{O}}2}{≤ft(1Δ\\right)} metastable singlet delta oxygen (SDO) as individual species. The role of surface loss and effective lifetime of SDO is discussed. To simulate different surface conditions, the SDO surface loss probability and the secondary electron emission coefficient were varied in the model. It is found that a change in surface condition significantly influences the metastable concentration, electronegativity, spatial particle distributions and densities as well as the ionization and electron heating dynamics. The excitation dynamics obtained from simulations are compared with PROES measurements. This allows to determine experimentally relevant SDO surface loss probabilities and secondary electron emission coefficient values in-situ and is demonstrated for two different surface materials, namely aluminum and Teflon.

  20. Disorder-induced heating of ultracold neutral plasmas created from atoms in partially filled optical lattices.

    PubMed

    Murphy, D; Sparkes, B M

    2016-08-01

    We quantify the disorder-induced heating (DIH) of ultracold neutral plasmas (UCNPs) created from cold atoms in optical lattices with partial filling fractions, using a conservation of energy model involving the spatial correlations of the initial state and the equation of state in thermal equilibrium for a one-component plasma. We show, for experimentally achievable filling fractions, that the ionic Coulomb coupling parameter could be increased to a degree comparable to other proposed DIH-mitigation schemes. Molecular dynamics simulations were performed with compensation for finite-size and periodic boundary effects, which agree with calculations using the model. Reduction of DIH using optical lattices will allow for the study of strongly coupled plasma physics using low-density, low-temperature, laboratory-based plasmas, and lead to improved brightness in UCNP-based cold electron and ion beams, where DIH is otherwise a fundamental limitation to beam focal sizes and diffraction imaging capability. PMID:27627236

  1. Inter-conversion of Work and Heat With Plasma Electric Fields

    SciTech Connect

    Avinash, K.

    2010-11-23

    Thermodynamics of a model system where a group of cold charged particles locally confined in a volume V{sub P} within a warm plasma of temperature T and fixed volume V (V{sub P}<plasma. Finally, the direct conversion of plasma heat into mechanical work is demonstrated via a Striling like engine cycle involving ES isothermal compression of plasma electric fields.

  2. Evolution of the electron temperature profile of ohmically heated plasmas in TFTR

    SciTech Connect

    Taylor, G.; Efthimion, P.C.; Arunasalam, V.; Goldston, R.J.; Grek, B.; Hill, K.W.; Johnson, D.W.; McGuire, K.; Ramsey, A.T.; Stauffer, F.J.

    1985-08-01

    Blackbody electron cyclotron emission was used to ascertain and study the evolution and behavior of the electron temperature profile in ohmically heated plasmas in the Tokamak Fusion Test Reactor (TFTR). The emission was measured with absolutely calibrated millimeter wavelength radiometers. The temperature profile normalized to the central temperature and minor radius is observed to broaden substantially with decreasing limiter safety factor q/sub a/, and is insensitive to the plasma minor radius. Sawtooth activity was seen in the core of most TFTR discharges and appeared to be associated with a flattening of the electron temperature profile within the plasma core where q less than or equal to 1. Two types of sawtooth behavior were identified in large TFTR plasmas (minor radius, a less than or equal to 0.8 m) : a typically 35 to 40 msec period ''normal'' sawtooth, and a ''compound'' sawtooth with 70 to 80 msec period.

  3. Disorder-induced heating of ultracold neutral plasmas created from atoms in partially filled optical lattices

    NASA Astrophysics Data System (ADS)

    Murphy, D.; Sparkes, B. M.

    2016-08-01

    We quantify the disorder-induced heating (DIH) of ultracold neutral plasmas (UCNPs) created from cold atoms in optical lattices with partial filling fractions, using a conservation of energy model involving the spatial correlations of the initial state and the equation of state in thermal equilibrium for a one-component plasma. We show, for experimentally achievable filling fractions, that the ionic Coulomb coupling parameter could be increased to a degree comparable to other proposed DIH-mitigation schemes. Molecular dynamics simulations were performed with compensation for finite-size and periodic boundary effects, which agree with calculations using the model. Reduction of DIH using optical lattices will allow for the study of strongly coupled plasma physics using low-density, low-temperature, laboratory-based plasmas, and lead to improved brightness in UCNP-based cold electron and ion beams, where DIH is otherwise a fundamental limitation to beam focal sizes and diffraction imaging capability.

  4. Bulk ion acceleration and particle heating during magnetic reconnection in a laboratory plasma

    SciTech Connect

    Yoo, Jongsoo; Yamada, Masaaki; Ji, Hantao; Jara-Almonte, Jonathan; Myers, Clayton E.

    2014-05-15

    Bulk ion acceleration and particle heating during magnetic reconnection are studied in the collisionless plasma of the Magnetic Reconnection Experiment (MRX). The plasma is in the two-fluid regime, where the motion of the ions is decoupled from that of the electrons within the ion diffusion region. The reconnection process studied here is quasi-symmetric since plasma parameters such as the magnitude of the reconnecting magnetic field, the plasma density, and temperature are compatible on each side of the current sheet. Our experimental data show that the in-plane (Hall) electric field plays a key role in ion heating and acceleration. The electrostatic potential that produces the in-plane electric field is established by electrons that are accelerated near the electron diffusion region. The in-plane profile of this electrostatic potential shows a “well” structure along the direction normal to the reconnection current sheet. This well becomes deeper and wider downstream as its boundary expands along the separatrices where the in-plane electric field is strongest. Since the in-plane electric field is 3–4 times larger than the out-of-plane reconnection electric field, it is the primary source of energy for the unmagnetized ions. With regard to ion acceleration, the Hall electric field causes ions near separatrices to be ballistically accelerated toward the outflow direction. Ion heating occurs as the accelerated ions travel into the high pressure downstream region. This downstream ion heating cannot be explained by classical, unmagnetized transport theory; instead, we conclude that ions are heated by re-magnetization of ions in the reconnection exhaust and collisions. Two-dimensional (2-D) simulations with the global geometry similar to MRX demonstrate downstream ion thermalization by the above mechanisms. Electrons are also significantly heated during reconnection. The electron temperature sharply increases across the separatrices and peaks just outside of the

  5. Localized electron heating and downstream density rise in expanding helicon plasma

    NASA Astrophysics Data System (ADS)

    Ghosh, Soumen; Barada, Kshitish; Chattopadhyay, Prabal; Ghosh, Joydeep; Bora, Dhiraj

    2015-11-01

    Localized electron heating and downstream density rise have been observed in presence of diverging magnetic fields in a linear expanding helicon plasma system. Axial wave field measurement shows the presence of damped helicon waves with standing wave character folded into it even at low densities (1016 m-3) . Helicon wavelength is just about twice the antenna length and the phase velocity (vp) is almost equal to the speed required for electron impact ionization. Observations advocate the Landau damping heating by the helicon waves, particularly in our low density plasma. Electron heating, confined away from the antenna centre, strongly indicates a source of local power absorption, occurring due to damped helicon waves. Further downstream from the location of electron heating, a density peak is observed. Location of both electron heating and density peaking can be varied by changing the axial magnetic field topology. A comprehensive discussion regarding the cause behind both the localized electron heating and downstream density rise will be discussed in this presentation.

  6. Growth enhancement effects of radish sprouts: atmospheric pressure plasma irradiation vs. heat shock

    NASA Astrophysics Data System (ADS)

    Sarinont, T.; Amano, T.; Kitazaki, S.; Koga, K.; Uchida, G.; Shiratani, M.; Hayashi, N.

    2014-06-01

    We compare growth enhancement effects due to atmospheric air dielectric barrier discharge plasma irradiation and heat shock to seeds of radish sprouts (Raphanus sativus L.). Interactions between radicals and seeds in a short duration of 3 min. lead to the growth enhancement of radish sprouts in a long term of 7 days and the maximum average length is 3.7 times as long as that of control. The growth enhancement effects become gradually weak with time, and hence the ratio of the average length for plasma irradiation to that for control decreases from 3.7 for the first day to 1.3 for 7 day. The average length for heat shock of 60°C for 10 min. and 100°C for 3 min. is longer than that for control, and the maximum average length is 1.3 times as long as that of control. Heat shock has little contribution to the growth enhancement due to plasma irradiation, because the maximum temperature due to plasma irradiation is less than 60°C.

  7. Analyses of core heat transport in plasmas with different toroidal rotation profiles in JT-60U

    NASA Astrophysics Data System (ADS)

    Narita, Emi; Honda, Mitsuru; Hayashi, Nobuhiko; Urano, Hajime; Ide, Shunsuke; Fukuda, Takeshi

    2013-10-01

    It has been reported that in H-mode plasmas, toroidal rotation in the co direction with respect to the plasma current is more favorable for energy confinement than that in the counter direction. Effects of toroidal rotation on core temperature profiles have been pointed out, whereas the improved confinement has been found to be due to an increase in the pedestal temperature with co-toroidal rotation and profile resilience. In JT-60U, roles of toroidal rotation have been studied using neutral beam injection changes. In this study, core heat transport of these plasmas with different toroidal rotation profiles is investigated with several transport models implemented in the transport code TOPICS. These transport models give the anomalous heat diffusivity and are tested against conventional H-mode plasmas in JT-60U. The calculations are performed with the E × B shear effect. The relationship between heat transport and toroidal rotation is examined with a flux-tube gyrokinetic code, which we will present in the paper. Work supported by JSPS Research Fellowships for Young Scientists.

  8. Radiative heat transfer in plasma of pulsed high pressure caesium discharge

    NASA Astrophysics Data System (ADS)

    Lapshin, V. F.

    2016-01-01

    Two-temperature many component gas dynamic model is used for the analysis of features of radiative heat transfer in pulsed high pressure caesium discharge plasma. It is shown that at a sufficiently high pressure the radial optical thickness of arc column is close to unit (τR (λ) ∼ 1) in most part of spectrum. In this case radiative heat transfer has not local character. In these conditions the photons which are emitted in any point of plasma volume are absorbed in other point remote from an emission point on considerable distance. As a result, the most part of the electric energy put in the discharge mainly near its axis is almost instantly redistributed on all volume of discharge column. In such discharge radial profiles of temperature are smooth. In case of low pressure, when discharge plasma is optically transparent for own radiation in the most part of a spectrum (τR(λ) << 1), the emission of radiation without reabsorption takes place. Radiative heat transfer in plasma has local character and profiles of temperature have considerable gradient.

  9. Overview of anisotropic flow measurements from ALICE

    NASA Astrophysics Data System (ADS)

    Zhou, You

    2016-05-01

    Anisotropic flow is an important observable to study the properties of the hot and dense matter, the Quark Gluon Plasma (QGP), created in heavy-ion collisions. Measurements of anisotropic flow for inclusive and identified charged hadrons are reported in Pb-Pb, p-Pb and pp collisions with the ALICE detector. The comparison of experimental measurements to various theoretical calculations are also presented in these proceedings.

  10. Design of TFTR movable limiter blades for ohmic and neutral-beam-heated plasmas

    SciTech Connect

    Doll, D.W.; Ulrickson, M.A.; Cecchi, J.L.; Citrolo, J.C.; Weissenburger, D.; Bialek, J.

    1981-10-01

    A new set of movable limiter blades has been designed for TFTR that will meet both the requirements of the 4 MW ohmic heated and the 33 MW neutral beam heated plasmas. This is accomplished with three limiter blades each having and elliptical shape along the toroidal direction. Heat flux levels are acceptable for both ohmic heated and pre-strong compression plasmas. The construction consists of graphite tiles attached to cooled backing plates. The tiles have an average thickness of approx. 4.7 cm and are drawn against the backing plate with spring loaded fasteners that are keyed into the graphite. The cooled backing plate provides the structure for resisting disruption and fault induced loads. A set of rollers attached to the top and bottom blades allow them to be expanded and closed in order to vary the plasma surface for scaling experiments. Water cooling lines penetrate only the mid-plane port cover/support plate in such a way as to avoid bolted water connections inside the vacuum boundary and at the same time allow blade movement. Both the upper and lower blades are attached to the mid-plane limiter blade through pivots. Pivot connections are protected against arcing with an alumina coating and a shunt bar strap. Remote handling is considered throughout the design.

  11. EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: X-ray spectral diagnostics of plasmas heated by picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Bryunetkin, B. A.; Skobelev, I. Yu; Faenov, A. Ya; Khakhalin, S. Ya; Kalashnikov, M. P.; Nickles, P. V.; Schnürer, M.

    1993-06-01

    The properties of a magnesium plasma heated by picosecond laser pulses have been determined by x-ray spectral methods. Experiments were carried out at a laser power density ~ 1.5 · 1018 W/cm2. The x-ray spectra were detected by spectrographs with a plane CsAP crystal and a mica crystal bent into part of a spherical surface 10 cm in radius. The experimental data are compared with predictions of a calculation on the time-varying kinetics of multiply charged magnesium ions.

  12. Electron residual energy due to stochastic heating in field-ionized plasma

    NASA Astrophysics Data System (ADS)

    Khalilzadeh, Elnaz; Yazdanpanah, Jam; Jahanpanah, Jafar; Chakhmachi, Amir; Yazdani, Elnaz

    2015-11-01

    The electron residual energy originated from the stochastic heating in under-dense field-ionized plasma is investigated here. Initially, the optical response of plasma is modeled by using two counter-propagating electromagnetic waves. In this case, the solution of motion equation of a single electron indicates that by including the ionization, the electron with higher residual energy compared with that without ionization could be obtained. In agreement with chaotic nature of the motion, it is found that the electron residual energy will be significantly changed by applying a minor change in the initial conditions. Extensive kinetic 1D-3V particle-in-cell simulations have been performed in order to resolve full plasma reactions. In this way, two different regimes of plasma behavior are observed by varying the pulse length. The results indicate that the amplitude of scattered fields in a proper long pulse length is high enough to act as a second counter-propagating wave and trigger the stochastic electron motion. On the contrary, the analyses of intensity spectrum reveal the fact that the dominant scattering mechanism tends to Thomson rather than Raman scattering by increasing the pulse length. A covariant formalism is used to describe the plasma heating so that it enables us to measure electron temperature inside and outside of the pulse region.

  13. Core Fueling and Edge Particle Flux Analysis in Ohmically and Auxiliary Heated NSTX Plasmas

    SciTech Connect

    V.A. Soukhanovskii; R. Maingi; R. Raman; H.W. Kugel; B.P. LeBlanc; L. Roquemore; C.H. Skinner; NSTX Research Team

    2002-06-12

    The Boundary Physics program of the National Spherical Torus Experiment (NSTX) is focusing on optimization of the edge power and particle flows in b * 25% L- and H-mode plasmas of t {approx} 0.8 s duration heated by up to 6 MW of high harmonic fast wave and up to 5 MW of neutral beam injection. Particle balance and core fueling efficiencies of low and high field side gas fueling of L-mode homic and NBI heated plasmas have been compared using an analytical zero dimensional particle balance model and measured ion and neutral fluxes. Gas fueling efficiencies are in the range of 0.05-0.20 and do not depend on discharge magnetic configuration, density or poloidal location of the injector. The particle balance modeling indicates that the addition of HFS fueling results in a reversal of the wall loading rate and higher wall inventories. Initial particle source estimates obtained from neutral pressure and spectroscopic measurements indicate that ion flux into the divertor greatly exceeds midplane ion flux from the main plasma, suggesting that the scrape-off cross-field transport plays a minor role in diverted plasmas. Present analysis provides the basis for detailed fluid modeling of core and edge particle flows and particle confinement properties of NSTX plasmas. This research was supported by the U.S. Department of Energy under contracts No. DE-AC02-76CH03073, DE-AC05-00OR22725, and W-7405-ENG-36.

  14. Electron residual energy due to stochastic heating in field-ionized plasma

    SciTech Connect

    Khalilzadeh, Elnaz; Yazdanpanah, Jam Chakhmachi, Amir; Jahanpanah, Jafar; Yazdani, Elnaz

    2015-11-15

    The electron residual energy originated from the stochastic heating in under-dense field-ionized plasma is investigated here. Initially, the optical response of plasma is modeled by using two counter-propagating electromagnetic waves. In this case, the solution of motion equation of a single electron indicates that by including the ionization, the electron with higher residual energy compared with that without ionization could be obtained. In agreement with chaotic nature of the motion, it is found that the electron residual energy will be significantly changed by applying a minor change in the initial conditions. Extensive kinetic 1D-3V particle-in-cell simulations have been performed in order to resolve full plasma reactions. In this way, two different regimes of plasma behavior are observed by varying the pulse length. The results indicate that the amplitude of scattered fields in a proper long pulse length is high enough to act as a second counter-propagating wave and trigger the stochastic electron motion. On the contrary, the analyses of intensity spectrum reveal the fact that the dominant scattering mechanism tends to Thomson rather than Raman scattering by increasing the pulse length. A covariant formalism is used to describe the plasma heating so that it enables us to measure electron temperature inside and outside of the pulse region.

  15. Plasma Sloshing in Pulse-heated Solar and Stellar Coronal Loops

    NASA Astrophysics Data System (ADS)

    Reale, F.

    2016-08-01

    There is evidence that coronal heating is highly intermittent, and flares are the high energy extreme. The properties of the heat pulses are difficult to constrain. Here, hydrodynamic loop modeling shows that several large amplitude oscillations (˜20% in density) are triggered in flare light curves if the duration of the heat pulse is shorter than the sound crossing time of the flaring loop. The reason for this is that the plasma does not have enough time to reach pressure equilibrium during heating, and traveling pressure fronts develop. The period is a few minutes for typical solar coronal loops, dictated by the sound crossing time in the decay phase. The long period and large amplitude make these oscillations different from typical magnetohydrodynamic (MHD) waves. This diagnostic can be applied both to observations of solar and stellar flares and to future observations of non-flaring loops at high resolution.

  16. Plasma Sloshing in Pulse-heated Solar and Stellar Coronal Loops

    NASA Astrophysics Data System (ADS)

    Reale, F.

    2016-08-01

    There is evidence that coronal heating is highly intermittent, and flares are the high energy extreme. The properties of the heat pulses are difficult to constrain. Here, hydrodynamic loop modeling shows that several large amplitude oscillations (∼20% in density) are triggered in flare light curves if the duration of the heat pulse is shorter than the sound crossing time of the flaring loop. The reason for this is that the plasma does not have enough time to reach pressure equilibrium during heating, and traveling pressure fronts develop. The period is a few minutes for typical solar coronal loops, dictated by the sound crossing time in the decay phase. The long period and large amplitude make these oscillations different from typical magnetohydrodynamic (MHD) waves. This diagnostic can be applied both to observations of solar and stellar flares and to future observations of non-flaring loops at high resolution.

  17. Halo plasma heating by neutral beam injection in TMX-U

    SciTech Connect

    Hsu, W.L.; Bauer, W.; Kerst, R.A.; Wilson, K.L.; Simonen, T.C.; Foote, J.H.; Pickles, W.L.

    1985-05-01

    The electron temperature and density of the halo in TMX-U have been measured by Langmuir probes to study the heating of the halo plasma by neutral beam injection. This study is motivated by the recent interest in using a pair of halo recyclers to enhance the halo density and thereby increase halo shielding. In present TMX-U operation, without halo recyclers, a halo density of 2 x 10/sup 12/ cm/sup -3/ with electron temperature of 20 eV has been measured during the heating phase with neutral beam injection only. A halo power balance model incorporating several heating mechanisms resulting from neutral beam injection is described. The model accurately predicts the measured temperatures. At the halo density range that one expects to achieve with halo recyclers, the model predicts the existing TMX-U neutral beam sources to heat the halo to at least 30 eV.

  18. The role of electron equation of state in heating partition of protons in a collisionless plasma

    SciTech Connect

    Parashar, Tulasi N.; Vasquez, Bernard J.; Markovskii, Sergei A.

    2014-02-15

    One of the outstanding questions related to the solar wind is the heating of solar wind plasma. Addressing this question requires a self consistent treatment of the kinetic physics of a collisionless plasma. A hybrid code (with particle ions and fluid electrons) is one of the most convenient computational tools, which allows us to explore self consistent ion kinetics, while saving us computational time as compared to the full particle in cell codes. A common assumption used in hybrid codes is that of isothermal electrons. In this paper, we discuss the role that the equation of state for electrons could potentially play in determining the ion kinetics.

  19. Device and method for electron beam heating of a high density plasma

    DOEpatents

    Thode, L.E.

    A device and method for relativistic electron beam heating of a high density plasma in a small localized region are described. A relativistic electron beam generator produces a high voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high density target plasma which typically comprises DT, DD, hydrogen boron or similar thermonuclear gas at a density of 10/sup 17/ to 10/sup 20/.

  20. Generalized parallel heat transport equations in collisional to weakly collisional plasmas

    SciTech Connect

    Zawaideh, E.; Kim, N.S.; Najmabadi, F.

    1988-11-01

    A new set of two-fluid heat transport equations that is valid from collisional to weakly collisional limits is derived. Starting from gyrokinetic equations in flux coordinates, a set of moment equations describing plasma energy transport along the field lines of a space- and time-dependent magnetic field is derived. No restrictions on the anisotropy of the ion distribution function or collisionality are imposed. In the highly collisional limit, these equations reduce to the classical heat conduction equation (e.g., Spitzer and Haerm or Braginskii), while in the weakly collisional limit, they describe a saturated heat flux (flux limited). Numerical examples comparing these equations with conventional heat transport equations show that in the limit where the ratio of the mean free path lambda to the scale length of the temperature gradient L/sub T/ approaches zero, there is no significant difference between the solutions of the new and conventional heat transport equations. As lambda/L/sub T/..-->..1, the conventional heat conduction equation contains a significantly larger error than (lambda/L/sub T/)/sup 2/. The error is found to be O(lambda/L)/sup 2/, where L is the smallest of the scale lengths of the gradient in the magnetic field, or the macroscopic plasma parameters (e.g., velocity scale length, temperature scale length, and density scale length). The accuracy of the flux-limited model depends significantly on the value of the flux limit parameter which, in general, is not known. The new set of equations shows that the flux-limited parameter is a function of the magnetic field and plasma parameter profiles.

  1. Ion Heating During Local Helicity Injection Plasma Startup in the Pegasus ST

    NASA Astrophysics Data System (ADS)

    Burke, M. G.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Perry, J. M.; Reusch, J. A.

    2015-11-01

    Plasmas in the Pegasus ST are initiated either through standard, MHD stable, inductive current drive or non-solenoidal local helicity injection (LHI) current drive with strong reconnection activity, providing a rich environment to study ion dynamics. During LHI discharges, a large amount of impurity ion heating has been observed, with the passively measured impurity Ti as high as 800 eV compared to Ti ~ 60 eV and Te ~ 175 eV during standard inductive current drive discharges. In addition, non-thermal ion velocity distributions are observed and appear to be strongest near the helicity injectors. The ion heating is hypothesized to be a result of large-scale magnetic reconnection activity, as the amount of heating scales with increasing fluctuation amplitude of the dominant, edge localized, n =1 MHD mode. An approximate temporal scaling of the heating with the amplitude of higher frequency magnetic fluctuations has also been observed, with large amounts of power spectral density present at several impurity ion cyclotron frequencies. Recent experiments have focused on investigating the impurity ion heating scaling with the ion charge to mass ratio as well as the reconnecting field strength. The ion charge to mass ratio was modified by observing different impurity charge states in similar LHI plasmas while the reconnecting field strength was modified by changing the amount of injected edge current. Work supported by US DOE grant DE-FG02-96ER54375.

  2. SiC/C nanocable structure produced in silicon carbide by arc plasma heating

    NASA Astrophysics Data System (ADS)

    Nayak, B. B.

    2012-01-01

    Defect-free and long SiC/C nanocables have been produced by heating SiC powder at 3000°C by employing dc arc plasma (Ar) in a specially designed configuration of graphite arc. Microstructural characterizations of the heat-treated powder carried out by TEM, HRTEM, SAED, EDS, and micro Raman spectroscopy showed the nanocables to consist of a SiC shell/sheath stuffed with wire type solid C core. A possible mechanism is discussed to explain the cable-type growth.

  3. On the role of stochastic heating in experiments with complex plasmas

    SciTech Connect

    Marmolino, C.; De Angelis, U.; Ivlev, A. V.; Morfill, G. E.

    2009-03-15

    Stochastic heating of dust particles resulting from dust charge fluctuations is considered in some laboratory situations, where high kinetic temperatures of dust particles have been suggested or could be observed. A particular case, in the conditions of the scrape-off layer in tokamak plasmas, is also considered and it is shown that kinetic energies corresponding to velocities of {approx_equal}km/s can be reached in times of order {approx_equal}1 ms by micron-size particles interacting with a background of stochastically heated nanosize particles.

  4. Statistical comparison of ICRF and NBI heating performance in JET-ILW L-mode plasmas

    SciTech Connect

    Lerche, E.; Van Eester, D.; Jacquet, Ph.; Mayoral, M.-L.; Graham, M.; Matthews, G.; Monakhov, I.; Rimini, F.; Colas, L.; Czarnecka, A.; Vries, P. de; Collaboration: JET-EFDA Contributors

    2014-02-12

    After the change over from the C-wall to the ITER-like Be/W wall (ILW) in JET, the radiation losses during ICRF heating have increased and are now substantially larger than those observed with NBI at the same power levels, in spite of the similar global plasma energies reached with the two heating systems. A comparison of the NBI and ICRF performances in the JET-ILW experiments, based on a statistical analysis of ∼3000 L-mode discharges, will be presented.

  5. ELM behaviour and linear MHD stability of edge ECRH heated ASDEX Upgrade plasmas

    NASA Astrophysics Data System (ADS)

    Burckhart, A.; Dunne, M.; Wolfrum, E.; Fischer, R.; McDermott, R.; Viezzer, E.; Willensdorfer, M.; the ASDEX Upgrade Team

    2016-05-01

    In order to test the peeling–ballooning ELM model, ECRH heating was applied to the edge of ASDEX Upgrade type-I ELMy H-mode plasmas to alter the pedestal pressure and current density profiles. The discharges were analysed with respect to ideal MHD stability. While the ELM frequency increased and the pedestal gradients relaxed with edge ECRH, the MHD stability boundary did not change. The results indicate that the peeling–ballooning model is insufficient to fully explain the triggering of ELM instabilities in the presence of edge ECRH heating.

  6. Plasma Heating to Super-Hot Temperatures (>30 MK) in the August 9, 2011 Solar Flare

    NASA Astrophysics Data System (ADS)

    Sharykin, Ivan; Struminsky, Alexei; Zimovets, Ivan

    2015-08-01

    We investigate the August 9, 2011 solar flare of X-ray class X6.9, the "hottest" flare from 2000 to 2012, with a peak plasma temperature according to GOES data of 33 MK. Our goal is to determine the cause of such an anomalously high plasma temperature and to investigate the energy balance in the flare region with allowance made for the presence of a super-hot plasma (>30 MK). We analyze the RHESSI, GOES, AIA/SDO, and EVE/SDO data and discuss the spatial structure of the flare region and the results of our spectral analysis of its X-ray emission. Our analysis of the RHESSI X-ray spectra is performed in the one-temperature and two-temperature approximations by taking into account the emission of hot (20 MK) and super-hot (45 MK) plasmas. The hard X-ray spectrum in both models is fitted by power laws. The observed peculiarities of the flare are shown to be better explained in terms of the two-temperature model, in which the super-hot plasma is located at the flare loop tops (or in the magnetic cusp region). The formation of the super-hot plasma can be associated with its heating through primary energy release and with the suppression of thermal conduction.

  7. Research on heating, instabilities, turbulence and RF emission from electric field dominated plasmas

    NASA Astrophysics Data System (ADS)

    Roth, J. R.; Alexeff, Igor

    1989-07-01

    This contract has supported four research programs: (1) a program of research on plasma turbulence; (2) a program of research on plasma heating by collisional magnetic pumping; (3) a research program on the Orbitron submillimeter maser; and (4) the initial phase of a program on plasma cloaking of military targets for protection against radar and directed microwave energy weapons. Progress in these areas is documented in the text of this final report and in the twenty archival publications included in the appendices to this report. In addition to the above four research areas, work was continued on plasma diagnostic development, and the development of new state-of-the-art data analysis and reduction methods, including software development for online reduction of Langmuir probe, capacitive probe, and other diagnostic information. Also being developed is the capability to analyze electrostatic potential fluctuations by the methods of nonlinear dynamics. An important part of the research program was the training of graduate and undergraduate research assistants in state-of-the-art methods in the fields of high temperature plasma physics, plasma diagnostics, communications, and related areas.

  8. Unique X-ray emission characteristics from volumetrically heated nanowire array plasmas

    NASA Astrophysics Data System (ADS)

    Rocca, J. J.; Bargsten, C.; Hollinger, R.; Shlyaptsev, V.; Pukhov, A.; Kaymak, V.; Capeluto, G.; Keiss, D.; Townsend, A.; Rockwood, A.; Wang, Y.; Wang, S.

    2015-11-01

    Highly anisotropic emission of hard X-ray radiation (h ν >10 keV) is observed when arrays of ordered nanowires (50 nm diameter wires of Au or Ni) are volumetrically heated by normal incidence irradiation with high contrast 50-60 fs laser pulses of relativistic intensity. The annular emission is in contrast with angular distribution of softer X-rays (h ν >1 KeV) from these targets and with the X-ray radiation emitted by polished flat targets, both of which are nearly isotropic. Model computations that make use the electron energy distribution computed by particle-in-cell simulations show that the unexpected annular distribution of the hard x-rays is the result of bremsstrahlung from fast electrons. Volumetric heating of Au nanowire arrays irradiated with an intensity of 2 x 10 19 W cm-2 is measured to convert laser energy into h ν>1KeV photons with a record efficiency of >8 percent into 2 π, creating a bright picosecond X-ray source for applications. Work supported by the Office of Fusion Energy Science of the U.S Department of Energy, and the Defense Threat Reduction Agency. A.P was supported by DFG project TR18.

  9. Preferential electron-cyclotron heating of hot electrons and formation of overdense plasmas

    NASA Astrophysics Data System (ADS)

    Quon, B. H.; Dandl, R. A.

    1989-10-01

    Three electron-cyclotron-heating techniques, which preferentially couple microwave power to different energy segments of the electron distribution function, have been experimentally investigated in the AMPHED facility [C. Bodeldijk, Special Supplement, Nucl. Fusion 26, 184 (1986)]. Whistler waves launched from the high-field mirror throat are strongly absorbed in a single pass across the resonant interaction layer, producing highly overdense cold background plasma but no relativistic hot particles. On the other hand, ordinary waves launched from the system side wall are only weakly damped, giving rise to local cylindrical cavity modes and preferential coupling to hot electrons in the 100 keV region. Low levels (≤5%) of upper-off-resonance heating power were shown to be most effective for preferential hot-electron plasma formation, with ˜100% of the injected power being absorbed by the energetic electrons.

  10. Current Drive and Plasma Heating by Electron Bernstein Waves in MAST

    SciTech Connect

    Shevchenko, V.

    2009-11-26

    Electron Bernstein waves (EBW) have the potential to provide highly localized heating and current drive (CD). EBWs are predominantly electrostatic and they damp on electrons near electron cyclotron harmonics without momentum injection into the plasma. These features represent a powerful tool for understanding transport and stability phenomena by locally perturbing the plasma and providing complementary CD methods in addition to neutral beams. The Mega-Ampere Spherical Tokamak (MAST) has a large cylindrical vacuum vessel and we have taken advantage of this to consider a number of launcher positions for RF power injection. The feasibility of EBW in the extended parameter space of MAST has been explored. Modelling was conducted with the EBW and BANDIT code package using a 'steady state' reference scenario with near zero loop voltage. Clear heating and CD effects have been identified for different launch configurations and frequencies.

  11. Effect of heat wave at the initial stage in spark plasma sintering.

    PubMed

    Zhang, Long; Zhang, Xiaomin; Chu, Zhongxiang; Peng, Song; Yan, Zimin; Liang, Yuan

    2016-01-01

    Thermal effects are important considerations at the initial stage in spark plasma sintering of non-conductive Al2O3 powders. The generalized thermo-elastic theory is introduced to describe the influence of the heat transport and thermal focusing caused by thermal wave propagation within a constrained space and transient time. Simulations show that low sintering temperature can realize high local temperature because of the superposition effect of heat waves. Thus, vacancy concentration differences between the sink and the cross section of the particles increase relative to that observed during pressure-less and hot-pressure sintering. Results show that vacancy concentration differences are significantly improved during spark plasma sintering, thereby decreasing the time required for sintering. PMID:27386287

  12. Ion internal transport barrier in neutral beam heated plasmas on HL-2A

    NASA Astrophysics Data System (ADS)

    Yu, D. L.; Wei, Y. L.; Liu, L.; Dong, J. Q.; Ida, K.; Itoh, K.; Sun, A. P.; Cao, J. Y.; Shi, Z. B.; Wang, Z. X.; Xiao, Y.; Yuan, B. S.; Du, H. R.; He, X. X.; Chen, W. J.; Ma, Q.; Itoh, S.-I.; Zhao, K. J.; Zhou, Y.; Wang, J.; Ji, X. Q.; Zhong, W. L.; Li, Y. G.; Gao, J. M.; Deng, W.; Liu, Yi; Xu, Y.; Yan, L. W.; Yang, Q. W.; Ding, X. T.; Duan, X. R.; Liu, Yong; HL-2A Team

    2016-05-01

    Ion internal transport barriers (iITBs) are first observed in neutral beam injection (NBI) heated plasmas at the HL-2A tokamak. The position of the barrier foot, in the stationary state, coincides with the q  =  1 surface within its uncertainty of measurement. iITBs can develop more easily at the beginning of NBI heating. Also, iITBs are unstable for the sawtooth plasma. Simulations reveal that the thermal diffusivity of ions (χ i) inside the barrier can be as low as the neoclassical level. It is observed that the flow shear in the stationary iITB state reaches the level required for suppressing the ion temperature gradient mode instability, which indicates the important role of flow shear in sustaining the iITB.

  13. Advances in High Harmonic Fast Wave Heating of NSTX H-mode Plasmas

    SciTech Connect

    Ryan, Philip Michael; Ahn, Joonwook; Bell, R. E.; Bonoli, P.; Chen, Guangye; Green, David L; Harvey, R. W.; Hosea, J.; Jaeger, Erwin Frederick; Kaye, S.; LeBlanc, B; Maingi, Rajesh; Phillips, Cynthia; Podesta, M.; Taylor, G.; Wilgen, John B; Wilson, J. R.

    2010-01-01

    High-harmonic fast wave (HHFW) heating and current drive is being developed in NSTX to provide bulk electron heating and q(0) control during non-inductively sustained Hmode plasmas fuelled by deuterium neutral-beam injection (NBI). In addition, it is used to assist the plasma current ramp-up. A major modification to increase the RF power limit was made in 2009; the original end-grounded, single end-powered current straps of the 12- element array were replaced with center-grounded, double end-powered straps. Greater than 3 MW have been coupled into NBI-driven, ELMy H-mode plasmas with this upgraded antenna. Improved core HHFW heating, particularly at longer wavelengths and during low-density start-up and plasma current ramp-up, has been obtained by lowering the edge density with lithium wall conditioning, thereby moving the critical density for fast-wave propagation away from the vessel wall [1]. Significant core electron heating of NBI-fuelled H-modes has been observed for the first time over a range of launched wavelengths and H-modes can be accessed by HHFW alone. Visible and IR camera images of the antenna and divertor indicate that fast wave interactions can deposit considerable RF energy on the outboard divertor plate, especially at longer wavelengths that begin to propagate closer to the vessel walls. Edge power loss can also arise from HHFWgenerated parametric decay instabilities; edge ion heating is observed that is wavelength dependent. During plasmas where HHFW is combined with NBI, there is a significant enhancement in neutron rate, and fast-ion D-alpha (FIDA) emission measurements clearly show broadening of the fast-ion profile in the plasma core. Large edge localized modes (ELMs) have been observed immediately following the termination of RF power, whether the power turn off is programmed or due to antenna arcing. Causality has not been established but new experiments are planned and will be reported. Fast digitization of the reflected power signal

  14. Long-term heat stress induces the inflammatory response in dairy cows revealed by plasma proteome analysis.

    PubMed

    Min, Li; Zheng, Nan; Zhao, Shengguo; Cheng, Jianbo; Yang, Yongxin; Zhang, Yangdong; Yang, Hongjian; Wang, Jiaqi

    2016-03-01

    In this work we employed a comparative proteomic approach to evaluate seasonal heat stress and investigate proteomic alterations in plasma of dairy cows. Twelve lactating Holstein dairy cows were used and the treatments were: heat stress (n = 6) in hot summer (at the beginning of the moderate heat stress) and no heat stress (n = 6) in spring natural ambient environment, respectively. Subsequently, heat stress treatment lasted 23 days (at the end of the moderate heat stress) to investigate the alterations of plasma proteins, which might be employed as long-term moderate heat stress response in dairy cows. Changes in plasma proteins were analyzed by two-dimensional electrophoresis (2-DE) combined with mass spectrometry. Analysis of the properties of the identified proteins revealed that the alterations of plasma proteins were related to inflammation in long-term moderate heat stress. Furthermore, the increase in plasma tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) directly demonstrated that long-term moderate heat stress caused an inflammatory response in dairy cows. PMID:26851364

  15. Numerical study of plasma generation process and internal antenna heat loadings in J-PARC RF negative ion source.

    PubMed

    Shibata, T; Nishida, K; Mochizuki, S; Mattei, S; Lettry, J; Hatayama, A; Ueno, A; Oguri, H; Ohkoshi, K; Ikegami, K; Takagi, A; Asano, H; Naito, F

    2016-02-01

    A numerical model of plasma transport and electromagnetic field in the J-PARC (Japan Proton Accelerator Research Complex) radio frequency ion source has been developed to understand the relation between antenna coil heat loadings and plasma production/transport processes. From the calculation, the local plasma density increase is observed in the region close to the antenna coil. Electrons are magnetized by the magnetic field line with absolute magnetic flux density 30-120 Gauss which leads to high local ionization rate. The results suggest that modification of magnetic configuration can be made to reduce plasma heat flux onto the antenna. PMID:26932010

  16. Accurately simulating anisotropic thermal conduction on a moving mesh

    NASA Astrophysics Data System (ADS)

    Kannan, Rahul; Springel, Volker; Pakmor, Rüdiger; Marinacci, Federico; Vogelsberger, Mark

    2016-05-01

    We present a novel implementation of an extremum preserving anisotropic diffusion solver for thermal conduction on the unstructured moving Voronoi mesh of the AREPO code. The method relies on splitting the one-sided facet fluxes into normal and oblique components, with the oblique fluxes being limited such that the total flux is both locally conservative and extremum preserving. The approach makes use of harmonic averaging points and a simple, robust interpolation scheme that works well for strong heterogeneous and anisotropic diffusion problems. Moreover, the required discretization stencil is small. Efficient fully implicit and semi-implicit time integration schemes are also implemented. We perform several numerical tests that evaluate the stability and accuracy of the scheme, including applications such as point explosions with heat conduction and calculations of convective instabilities in conducting plasmas. The new implementation is suitable for studying important astrophysical phenomena, such as the conductive heat transport in galaxy clusters, the evolution of supernova remnants, or the distribution of heat from black hole-driven jets into the intracluster medium.

  17. On heat conduction in multicomponent, non-Maxwellian spherically symmetric solar wind plasmas

    NASA Technical Reports Server (NTRS)

    Cuperman, S.; Dryer, M.

    1985-01-01

    A generalized expression for the steady-state heat flux in multicomponent, moderately non-Maxwellian spherically symmetric plasmas is presented and discussed. The work was motivated by the inability of the simple, Fourier-type formula for the thermal conductivity to explain the observed correlations in the solar wind. The results hold for situations not far from local thermodynamic equilibrium. The generalized expression includes not only correlations that have been observed but also correlations not sought for previously.

  18. Ion heating in a dusty plasma due to the dust/ion acoustic instability

    SciTech Connect

    Winske, D.; Gary, S.P.; Jones, M.E.

    1995-08-01

    The drift of plasma ions relative to charged grains in a dusty plasma can give rise to a dust/ion acoustic instability. The authors investigate the linear properties of the instability by numerically solving an appropriate linear dispersion equation and examine the nonlinear behavior through one-dimensional electrostatic particle simulations, in which the plasma and dust ions are treated as discrete particles and the electrons are modeled as a Boltzmann fluid. The instability is slightly weaker when the dust particles have a range of sizes, and corresponding range of charges and masses. It is argued that due to dust particles that comprise planetary rings, this process can contribute to ion heating and diffusion observed in the linear magnetosphere of Saturn. 14 refs., 4 figs.

  19. Analysis of High-Te Plasmas Heated by HHFW in NSTX

    SciTech Connect

    LeBlanc, P.; Bell, R. E.; Bonoli, P.; Hosea, J. C.; Mazzucato, E.; Phillips, C. K.; Roquemore, A. L.; Ryan, P. M.; Taylor, G.; Wilson, J. R.; Yuh, H.

    2009-06-26

    The implementation in TRANSP of a recent version of TORIC capable of calculating power deposition for HHFW conditions is used to analyze NSTX plasma under different operating conditions. The power deposition profile into the electrons is obtained for high-Te conditions - Te ≤ 5keV - obtained in He and D plasmas with ITB. HHFW heating of NBI-induced H-mode plasmas is discussed. At the RF onset the RF power is divided evenly between the electrons and the fast particles, but as the latter thermalize and the electron density increases, the HHFW power repartition shifts progressively toward the electrons. Power deposition profiles for the electrons and for the fast particles are shown.

  20. Analysis of High-T{sub e} Plasmas Heated by HHFW in NSTX

    SciTech Connect

    LeBlanc, B. P.; Bell, R. E.; Hosea, J. C.; Mazzucato, E.; Phillips, C. K.; Roquemore, A. L.; Taylor, G.; Wilson, J. R.; Bonoli, P.; Ryan, P. M.; Yuh, H.

    2009-11-26

    The implementation in TRANSP of a recent version of TORIC capable of calculating power deposition for HHFW conditions is used to analyze NSTX plasma under different operating conditions. The power deposition profile into the electrons is obtained for high-T{sub e} conditions - T{sub e}{<=}5 keV - obtained in He and D plasmas with ITB. HHFW heating of NBI-induced H-mode plasmas is discussed. At the RF onset the RF power is divided evenly between the electrons and the fast particles, but as the latter thermalize and the electron density increases, the HHFW power repartition shifts progressively toward the electrons. Power deposition profiles for the electrons and for the fast particles are shown.

  1. Secondary electron emission and the bifurcation of the heat flux to the targets in fusion plasmas

    SciTech Connect

    Lee, Wonjae; Krasheninnikov, Sergei I.

    2013-12-15

    The presence of secondary electron emission (SEE) from plasma facing components in fusion devices can result in a strong localization of the heat flux from plasma to the wall and subsequent wall erosion. Usually, the impact of the SEE is considered assuming the Maxwellian distribution of the electrons coming to the surface. As a result, the SEE coefficient only depends on the temperature of primary electrons. However, the tail of primary electron distribution function in the scrape off layer (SOL) of fusion devices can be far from Maxwellian due to preferential loss of fast electrons. Consequently, it is shown that the SEE coefficient will depend on the wall potential and multiple solutions can be possible corresponding to different regimes of plasma flow to the wall: with and without SEE effects. This effect can cause two-slope electron temperature profiles in the SOL, which are often seen in experiments.

  2. A self-consistent view on plasma-neutral interaction near a wall: plasma acceleration by momentum removal and heating by cold walls

    NASA Astrophysics Data System (ADS)

    van Rooij, Gerard; den Harder, Niek; Minea, Teofil; Shumack, Amy; de Blank, H.; Plasma Physics Team

    2014-10-01

    In plasma physics, material walls are generally regarded as perfect sinks for charged particles and their energy. A special case arises when the wall efficiently reflects the neutralized plasma particles (with a significant portion of their kinetic energy) and at the same time the upstream plasma is of sufficiently high density to yield strong neutral-ion coupling (i.e. reflected energy and momentum will not escape from the plasma). Under these conditions, plasma-surface interaction will feedback to the upstream plasma and a self-consistent view on the coupling between plasma and neutrals is required for correct prediction of plasma conditions and plasma-surface interaction. Here, an analytical and numerical study of the fluid equations is combined with experiments (in hydrogen and argon) to construct such a self-consistent view. It shows how plasma momentum removal builds up upstream pressure and causes plasma acceleration towards the wall. It also shows how energy reflection causes plasma heating, which recycles part of the reflected power to the wall and induces additional flow acceleration due to local sound speed increase. The findings are relevant as generic textbook example and are at play in the boundary plasma of fusion devices.

  3. Observations of Plasma Turbulence and Heating from the Solar Wind and Simulations

    NASA Astrophysics Data System (ADS)

    Wicks, R. T.

    2015-12-01

    The cascade of energy by plasma turbulence has been shown to occur in, and heat, the solar wind. Recent work in the study of solar wind turbulence has focussed, in the most part, on advanced data analysis techniques, such as third moment structure functions, wavelets, conditional data sampling, multi-spacecraft observations and reconstruction of 2D k-spectra with tomography, and statistical studies from long time series of spacecraft observations. These techniques are complex and contain different assumptions about the qualities of the data underpinning the measurements. Here, we will review recent advances and discoveries in the study of plasma turbulence from solar wind data analysis and discuss how benchmarking of techniques against one another could be pursued and how simulations can be used to aid in the understanding of the results of solar wind data analysis, in particular in the framework of the "Turbulence Dissipation Challenge" (Parashar et al., Journal of Plasma Physics, Volume 81, Issue 05, 905810513, 2015). We will pay particular attention to observing two different heating mechanisms: stochastic heating and resonant wave-particle interactions. The magnetic helicity of the solar wind is shown to separate into two distinct components, one originating from pseudo-Alfvenic (k may have a component parallel to the magnetic field) and one from the Alfvenic fluctuations (k is strictly perpendicular). The solar wind results are compared with "pseudo-spacecraft" data from large 3D PIC simulations.

  4. Recent results from the electron cyclotron heated plasmas in Tokamak à Configuration Variable (TCV)

    NASA Astrophysics Data System (ADS)

    Henderson, M. A.; Alberti, S.; Angioni, C.; Arnoux, G.; Behn, R.; Blanchard, P.; Bosshard, P.; Camenen, Y.; Coda, S.; Condrea, I.; Goodman, T. P.; Hofmann, F.; Hogge, J.-Ph.; Karpushov, A.; Manini, A.; Martynov, An.; Moret, J.-M.; Nikkola, P.; Nelson-Melby, E.; Pochelon, A.; Porte, L.; Sauter, O.; Ahmed, S. M.; Andrèbe, Y.; Appert, K.; Chavan, R.; Degeling, A.; Duval, B. P.; Etienne, P.; Fasel, D.; Fasoli, A.; Favez, J.-Y.; Furno, I.; Horacek, J.; Isoz, P.; Joye, B.; Klimanov, I.; Lavanchy, P.; Lister, J. B.; Llobet, X.; Magnin, J.-C.; Marlétaz, B.; Marmillod, P.; Martin, Y.; Mayor, J.-M.; Mylnar, J.; Paris, P. J.; Perez, A.; Peysson, Y.; Pitts, R. A.; Raju, D.; Reimerdes, H.; Scarabosio, A.; Scavino, E.; Seo, S. H.; Siravo, U.; Sushkov, A.; Tonetti, G.; Tran, M. Q.; Weisen, H.; Wischmeier, M.; Zabolotsky, A.; Yhuang, G.

    2003-05-01

    In noninductively driven discharges, 0.9 MW second harmonic (X2) off-axis co-electron cyclotron current drive deposition is combined with 0.45 MW X2 central heating to create an electron internal transport barrier (eITB) in steady plasma conditions resulting in a 1.6-fold increase of the confinement time (τEe) over ITER-98L-mode scaling. The eITB is associated with a reversed shear current profile enhanced by a large bootstrap current fraction (up to 80%) and is sustained for up to 10 current redistribution times. A linear dependence of the confinement improvement on the product of the global shear reversal factor (q0/qmin) and the reversed shear volume (ρq-min2) is shown. In other discharges heated with X2 the sawteeth are destabilized (respectively stabilized) when heating just inside (respectively outside) the q=1 surface. Control of the sawteeth may allow the avoidance of neoclassical tearing modes that can be seeded by the sawtooth instability. Results on H-mode and highly elongated plasmas using the newly completed third harmonic (X3) system and achieving up to 100% absorption are also discussed, along with comparison of experimental results with the TORAY-GA ray tracing code [K. Matsuda, IEEE Trans. Plasma Sci. PS-17, 6 (1989); R. H. Cohen, Phys. Fluids 30, 2442 (1987)].

  5. Kinetic Energy Oscillations during Disorder Induced Heating in an Ultracold Plasma

    NASA Astrophysics Data System (ADS)

    Langin, Thomas; McQuillen, Patrick; Strickler, Trevor; Pohl, Thomas; Killian, Thomas

    2015-05-01

    Ultracold neutral plasmas of strontium are generated by photoionizing laser-cooled atoms at temperature TMOT ~ 10 mK and density n ~1016 m-3 in a magneto-optical trap (MOT). After photoionization, the ions heat to ~ 1 K by a mechanism known as Disorder Induced Heating (DIH). During DIH kinetic energy oscillations (KEO) occur at a frequency ~ 2ωpi , where ωpi is the plasma frequency, indicating coupling to collective modes of the plasma. Electron screening also comes into play by changing the interaction from a Coulomb to a Yukawa interaction. Although DIH has been previously studied, improved measurements combined with molecular dynamics (MD) simulations allow us to probe new aspects. We demonstrate a measurement of the damping of the KEO due to electron screening which agrees with the MD simulations. We show that the MD simulations can be used to fit experimental DIH curves for plasma density n, resulting in very accurate density measurements. Finally, we discuss how ion temperature measurements are affected by the non-thermal distribution of the ions during the early stages of DIH. This work was supported by the United States National Science Foundation and the Department of Energy (PHY-0714603), the Air Force Office of Scientific Research (FA9550- 12-1-0267), the Shell Foundation, and the Department of Defense (NDSEG Fellowship)

  6. The effect of plasma heating on sublimation-driven flow in Io's atmosphere

    NASA Technical Reports Server (NTRS)

    Wong, Mau C.; Johnson, Robert E.

    1995-01-01

    The atmospheric flow on Io is numerically computed in a flat 2-D axisymmetric geometry for a sublimation atmosphere on the trailing hemisphere subjected to plasma bombardment, UV heating, and IR cooling. Calculations are performed for subsolar vapor pressures of approximately 6.5 x 10(exp -3) Pa (approximately 3 x 10(exp 18) SO2/sq cm) and 6.8 x 10(exp -4) Pa (approximately 4 x 10(exp 17) SO2/sq cm); the latter approximates the vapor pressure of F. P. Fanale et al. (1982). The amount of plasma energy deposited in the atmosphere is 20% of the plasma flow energy due to corotation (J. A. Linker et al., 1988). It is found that plasma heating significantly inflates the upper atmosphere, increasing both the exobase altitude and the amount of surface covered by more than an exospheric column of gas. This in turn controls the supply of the Io plasma torus (M. A. McGrath and R. E. Johnson, 1987). The horizontal flow of mass and energy is also important in determining the exobase altitude; and it is shown that IR cooling can be important, although our use of the equilibrium, cool-to-space approximation for a pure SO2 gas (E. Lellouch et al., 1992) may overestimate this effect. The calculated exobase altitudes are somewhat lower than those suggested by McGrath and Johnson (1987) for supplying the torus, indicating the details of the plasma energy deposition and sputter ejection rate near the exobase, as well as the IR emission from this region need to be examined. In addition, the molecules sublimed (or sputtered) from the surface are transported to the exobase in times short compared to the molecular photodissociation time. Therefore, the exobase is dominated by molecular species and the exobase is supplied by a small region of the surface.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

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

    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.

  9. Ion Dynamics and ICRH Heating in the Exhaust Plasma of The VASIMR Engine

    NASA Astrophysics Data System (ADS)

    Bering, E. A., III; Chang-Díaz, F. R.; Squire, J. P.; Jacobson, V.; Ilin, A.; Winter, D. S.; Bengtson, R. D.; Gibson, J. N.; Glober, T. W.; Brukardt, M.; Rodriguez, W.

    2002-01-01

    The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is a high power, radio frequency-driven magnetoplasma rocket, capable of Isp/thrust modulation at constant power. The plasma is produced by an integrated helicon discharge. However, the bulk of the plasma energy is added in a separate downstream stage by ion cyclotron resonance heating (ICRH.) Axial momentum is obtained by the adiabatic expansion of the plasma in a magnetic nozzle. Exhaust variation in the VASIMR is primarily achieved by the selective partitioning of the RF power to the helicon and ICRH systems, with the proper adjustment of the propellant flow. A laboratory simulation of the 25 kW proof of concept VASIMIR engine has been under development and test at NASA-JSC for several years. Experimentally, high density, stable plasma discharges have been generated in Helium, Hydrogen, Deuterium, Argon and Xenon. This paper will review the plasma diagnostic results obtained in 2000-2002 in a continuing series of performance optimization and design development studies. Available plasma diagnostics include a triple probe, a Mach probe, a bolometer, a television monitor, an H- photometer, a spectrometer, neutral gas pressure and flow measurements, several gridded energy analyzers (retarding potential analyzer or RPA), a surface recombination probe system, an emission probe, a directional, steerable RPA and other diagnostics. Reciprocating Langmuir and Mach probes are the primary plasma diagnostics. The Langmuir probe measures electron density and temperature profiles while the Mach probe measures flow profiles. Together this gives total plasma particle flux. An array of thermocouples provides a temperature map of the system. Ion flow velocities are estimated through three techniques: Mach probes, retarding potential analyzer, and spectroscopic measurements. During 2000-2002, we have performed a series of experiments on the VASIMR apparatus with several objectives, to explore the parameter space that

  10. Bifurcation physics of magnetic islands and stochasticity explored by heat pulse propagation studies in toroidal plasmas

    NASA Astrophysics Data System (ADS)

    Ida, K.; Kobayashi, T.; Yoshinuma, M.; Suzuki, Y.; Narushima, Y.; Evans, T. E.; Ohdachi, S.; Tsuchiya, H.; Inagaki, S.; Itoh, K.

    2016-09-01

    Bifurcation physics of a magnetic island was investigated using the heat pulse propagation technique produced by the modulation of electron cyclotron heating. There are two types of bifurcation phenomena observed in a large helical device (LHD) and DIII-D. One is a bifurcation of the magnetic topology between nested and stochastic fields. The nested state is characterized by the bi-directional (inward and outward) propagation of the heat pulse with slow propagation speed. The stochastic state is characterized by the fast propagation of the heat pulse with electron temperature flattening. The other bifurcation is between the magnetic island with larger thermal diffusivity and that with smaller thermal diffusivity. The damping of toroidal flow is observed at the O-point of the magnetic island both in helical plasmas and in tokamak plasmas during a mode locking phase with strong flow shears at the boundary of the magnetic island. Associated with the stochastization of the magnetic field, the abrupt damping of toroidal flow is observed in LHD. The toroidal flow shear shows a linear decay, while the ion temperature gradient shows an exponential decay. This observation suggests that this flow damping is due to the change in the non-diffusive term of momentum transport.

  11. Thermodynamic Structure of Collision-Dominated Expanding Plasma: Heating of Interplanetary Coronal Mass Injections

    NASA Technical Reports Server (NTRS)

    Liu, Y.; Richardson, J. D.; Belcher, J. W.; Kasper, J. C.; Elliott, H. A.

    2006-01-01

    We investigate the thermodynamic structure of interplanetary coronal mass ejections (ICMEs) using combined surveys of the ejecta between 0.3 and 20 AU. ICMEs are shown to have a moderate expansion in the solar wind compared with theoretical predictions. The expansion seems to be governed by a polytrope with gamma approx. 1.3 in this distance range. We find that Coulomb collisions are important contributors to the ion-ion equilibration process in the ICME plasma. The alpha-proton differential speed quickly drops to below 10 km/s due to strong Coulomb collisions. However, the two species of particles are far from thermal equilibrium with a temperature ratio T(sub alpha/T(sub p) = 4-6, suggestive of a preferential heating of alpha particles. The plasma heating rate as a function of heliocentric &stance required for the temperature profile is deduced by taking into account the expansion and energy transfer between protons and alphas via Coulomb collisions. The turbulence dissipation rate is also inferred from the inertial range power spectrum of magnetic fluctuations within ICMEs. Comparison of the turbulence dissipation rate with the required heating rate shows that turbulence dissipation seems sufficient to explain the ICME heating. Sources powering the turbulence are also investigated by examining the instabilities induced by temperature anisotropies and energy deposition by pickup ions.

  12. Heat flux in a non-Maxwellian plasma. [in realistic solar coronal loop

    NASA Technical Reports Server (NTRS)

    Ljepojevic, N. N.; Macneice, P.

    1989-01-01

    A hybrid numerical scheme is applied to solve the Landau equation for the electron distribution function over all velocity space. Evidence is presented for the first time of the degree and character of the failure of the classical Spitzer-Haerm heat flux approximation in a realistic solar coronal loop structure. In the loop model used, the failure is so severe at some points that the role of the heat flux in the plasma's energy balance is completely misinterpreted. In the lower corona the Spitzer-Haerm approximation predicts that the heat flux should act as an energy source, whereas the more accurate distribution functions calculated here show this to be an energy sink.

  13. A Radiative Transport Model for Heating Paints using High Density Plasma Arc Lamps

    SciTech Connect

    Sabau, Adrian S; Duty, Chad E; Dinwiddie, Ralph Barton; Nichols, Mark; Blue, Craig A; Ott, Ronald D

    2009-01-01

    The energy distribution and ensuing temperature evolution within paint-like systems under the influence of infrared radiation was studied. Thermal radiation effects as well as those due to heat conduction were considered. A complete set of material properties was derived and discussed. Infrared measurements were conducted to obtain experimental data for the temperature in the paint film. The heat flux of the incident radiation from the plasma arc lamp was measured using a heat flux sensor with a very short response time. The comparison between the computed and experimental results for temperature show that the models that are based on spectral four-flux RTE and accurate optical properties yield accurate results for the black paint systems.

  14. Interphase Momentum and Heat Exchange in Turbulent Dust-Laden Plasma Jet under Continuous Radial Powder Injection

    SciTech Connect

    Solonenko, Oleg P.; Smirnov, Audrey V.

    2006-05-05

    Potential possibilities of an advanced approach based on the usage of DC cascade torch providing an axially symmetric plasma jet outflow, and continuous radial injection of powder into a plasma flow are discussed. Comparison is made of the results, obtained using two models of interphase heat and momentum exchange between polydisperse alumina particles and air plasma jet, other factors being the same. The widely used model of gradientless particles' heating was applied for computing the two-phase plasma jets' temperature and velocity fields. The model is compared with corresponding model of gradient particle heating computed by using an efficient numerical method developed. Calculations were conducted under different scales of dense loading conditions to estimate the maximum productivity of plasma spray process.

  15. Evidence of weak plasma series resonance heating in the H-mode of neon and neon/argon inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Boffard, John B.; Jung, R. O.; Lin, Chun C.; Aneskavich, L. E.; Wendt, A. E.

    2012-09-01

    Phase-resolved optical emission spectroscopy measurements in argon and neon inductively coupled plasmas (ICPs) have revealed a surplus of high-energy electrons in neon-containing plasmas. Differences between results of emission model analyses using neon and argon lines (as well as probe measurements) also indicate a high-energy enhancement in neon-containing plasmas. The abundance of these extra high-energy electrons is correlated with the sheath thickness near the rf antenna and can be reduced by either adding a Faraday shield (external shielding) or increasing the plasma density. A comparison of modelled and experimental values of the 13.56 MHz time modulation of select neon emission lines strongly suggests plasma series resonance heating adjacent to the ICP antenna as the source of the extra heating.

  16. Device and method for electron beam heating of a high density plasma

    DOEpatents

    Thode, Lester E.

    1981-01-01

    A device and method for relativistic electron beam heating of a high density plasma in a small localized region. A relativistic electron beam generator produces a high voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high density target plasma which typically comprises DT, DD, hydrogen boron or similar thermonuclear gas at a density of 10.sup.17 to 10.sup.20 electrons per cubic centimeter. The target plasma is ionized prior to application of the electron beam by means of a laser or other preionization source. Utilizing a relativistic electron beam with an individual particle energy exceeding 3 MeV, classical scattering by relativistic electrons passing through isolation foils is negligible. As a result, relativistic streaming instabilities are initiated within the high density target plasma causing the relativistic electron beam to efficiently deposit its energy into a small localized region within the high density plasma target.

  17. High-power microwave transmission and launching systems for fusion plasma heating systems

    SciTech Connect

    Bigelow, T.S.

    1989-01-01

    Microwave power in the 30- to 300-GHz frequency range is becoming widely used for heating of plasma in present-day fusion energy magnetic confinement experiments. Microwave power is effective in ionizing plasma and heating electrons through the electron cyclotron heating (ECH) process. Since the power is absorbed in regions of the magnetic field where resonance occurs and launching antennas with narrow beam widths are possible, power deposition location can be highly controlled. This is important for maximizing the power utilization efficiency and improving plasma parameters. Development of the gyrotron oscillator tube has advanced in recent years so that a 1-MW continuous-wave, 140-GHz power source will soon be available. Gyrotron output power is typically in a circular waveguide propagating a circular electric mode (such as TE/sub 0,2/) or a whispering-gallery mode (such as TE/sub 15,2/), depending on frequency and power level. An alternative high-power microwave source currently under development is the free-electron laser (FEL), which may be capable of generating 2-10 MW of average power at frequencies of up to 500 GHz. The FEL has a rectangular output waveguide carrying the TE/sub 0,1/ mode. Because of its higher complexity and cost, the high-average-power FEL is not yet as extensively developed as the gyrotron. In this paper, several types of operating ECH transmission systems are discussed, as well systems currently being developed. The trend in this area is toward higher power and frequency due to the improvements in plasma density and temperature possible. Every system requires a variety of components, such as mode converters, waveguide bends, launchers, and directional couplers. Some of these components are discussed here, along with ongoing work to improve their performance. 8 refs.

  18. Plasma hyperosmolality and arterial pressure regulation during heating in dehydrated and awake rats.

    PubMed

    Nakajima, Y; Nose, H; Takamata, A

    1998-11-01

    To gain better insights into the effect of dehydration on thermal and cardiovascular regulation during hyperthermia, we examined these regulatory responses during body heating in rats under isosmotic hypovolemia and hyperosmotic hypovolemia. Rats were divided into four groups: normovolemic and isosmotic (C), hypovolemic and isosmotic [L, plasma volume loss (DeltaPV) = -20% of control], hypovolemic and less hyperosmotic [HL1, increase in plasma osmolality (DeltaPosm) = 23 mosmol/kgH2O, DeltaPV = -16%], and hypovolemic and more hyperosmotic (HL2, DeltaPosm = 52 mosmol/kgH2O, DeltaPV = -17%). Hyperosmolality was attained by subcutaneous injection of hypertonic saline and hypovolemia by intra-arterial injection of furosemide before heating. Then rats were placed in a thermocontrolled box (35 degreesC air temperature, approximately 20% relative humidity) for 1-2 h until rectal temperatures (Tre) reached 40.0 degreesC. Mean arterial pressure in L decreased with rise in Tre (P < 0.001), whereas mean arterial pressure remained constant in the other groups. Maximal tail skin blood flow in L, HL1, and HL2 was decreased to approximately 30% of that in C (P < 0. 001). Tre threshold for tail skin vasodilation (TVD) was not changed in L, whereas the threshold shifted higher in the HL groups. Tre threshold for TVD was highly correlated with Posm (r = 0.94, P < 0. 001). Heart rate in the HL groups increased with rise in Tre (P < 0. 001), whereas it remained unchanged in C and L. Cardiovascular responses to heating were not influenced by V1 antagonist in C, L, and HL2. Thus isotonic hypovolemia attenuates maximal tail skin blood flow, whereas hypertonic hypovolemia causes an upward shift of Tre threshold for TVD and an increase in heart rate during hyperthermia. These results suggest that plasma hyperosmolality stimulates pressor responses in the hypovolemic condition that subsequently contribute to arterial pressure regulation during heat stress. PMID:9791093

  19. Ultrahigh heat flux plasma-facing components for magnetic fusion energy

    SciTech Connect

    Youchison, D. L.

    2012-03-01

    Sandia and Ultramet partnered to design and test refractory metal plasma-facing components and heat exchangers for advanced, high-temperature power conversion systems. These devices consisted of high-temperature helium-to-helium and lithium-to-helium heat exchangers that operate with high efficiency due to the porous foam inserts used in the gas stream, which promote turbulence and provide extended surface area for enhanced convection. Single- and multi-channel helium panels and the Li-He heat exchanger were fabricated from either pure molybdenum, TZM, or tungsten. The design was carried out through an Ultramet subcontractor. The flow path was carefully tailored to minimize the pressure drop while maximizing the heat transfer. The single- and multi-channel helium panels were tested at Sandia's PMTF using an electron beam system and the closed helium flow loop. In 2006, a single-channel tungsten tube was successfully tested to an average heat flux of 14 MW/m{sup 2} with a localized peak of 22 MW/m{sup 2} along the axial centerline at the outer radius. Under this CRADA, multiple square-channel molybdenum components were successfully tested to heat flux levels approaching 8.5 MW/m{sup 2}. The three multi-channel prototypes experienced mechanical failure due to issues related to the design of the large unsupported span of the heated faceplates in combination with prototype material and braze selection. The Li-He heat exchanger was both designed and partially tested at the PMTF for helium and lithium flow.

  20. 21nm x-ray laser Thomson scattering of laser-heated exploding foil plasmas

    SciTech Connect

    Dunn, J; Rus, B; Mocek, T; Nelson, A J; Foord, M E; Rozmus, W; Baldis, H A; Shepherd, R L; Kozlova, M; Polan, J; Homer, P; Stupka, M

    2007-09-26

    Recent experiments were carried out on the Prague Asterix Laser System (PALS) towards the demonstration of a soft x-ray laser Thomson scattering diagnostic for a laser-produced exploding foil. The Thomson probe utilized the Ne-like zinc x-ray laser which was double-passed to deliver {approx}1 mJ of focused energy at 21.2 nm wavelength and lasting {approx}100 ps. The plasma under study was heated single-sided using a Gaussian 300-ps pulse of 438-nm light (3{omega} of the PALS iodine laser) at laser irradiances of 10{sup 13}-10{sup 14} W cm{sup -2}. Electron densities of 10{sup 20}-10{sup 22} cm{sup -3} and electron temperatures from 200 to 500 eV were probed at 0.5 or 1 ns after the peak of the heating pulse during the foil plasma expansion. A flat-field 1200 line mm{sup -1} variable-spaced grating spectrometer with a cooled charge-coupled device readout viewed the plasma in the forward direction at 30{sup o} with respect to the x-ray laser probe. We show results from plasmas generated from {approx}1 {micro}m thick targets of Al and polypropylene (C{sub 3}H{sub 6}). Numerical simulations of the Thomson scattering cross-sections will be presented. These simulations show electron peaks in addition to a narrow ion feature due to collective (incoherent) Thomson scattering. The electron features are shifted from the frequency of the scattered radiation approximately by the electron plasma frequency {+-}{omega}{sub pe} and scale as n{sub e}{sup 1/2}.

  1. ELM simulation experiments using transient heat and particle load produced by a magnetized coaxial plasma gun

    NASA Astrophysics Data System (ADS)

    Shoda, K.; Sakuma, I.; Iwamoto, D.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2011-10-01

    It is considered that thermal transient events such as type I edge-localized modes (ELMs) and disruptions will limit the lifetime of plasma-facing components (PFCs) in ITER. It is predicted that the heat load onto the PFCs during type I ELMs in ITER is 0.2-2MJ/m2 with pulse length of ~0.1-1ms. We have investigated interaction between transient heat and particle load and the PFCs by using a magnetized coaxial plasma gun (MCPG) at University of Hyogo. In the experiment, a pulsed plasma with duration of ~0.5ms, incident ion energy of ~30eV, and surface absorbed energy density of ~0.3-0.7MJ/m2 was produced by the MCPG. However, no melting occurred on a tungsten surface exposed to a single plasma pulse of ~0.7MJ/m2, while cracks clearly appeared at the edge part of the W surface. Thus, we have recently started to improve the performance of the MCPG in order to investigate melt layer dynamics of a tungsten surface such as vapor cloud formation. In the modified MCPG, the capacitor bank energy for the plasma discharge is increased from 24.5 kJ to 144 kJ. In the preliminary experiments, the plasmoid with duration of ~0.6 ms, incident ion energy of ~ 40 eV, and the surface absorbed energy density of ~2 MJ/m2 was successfully produced at the gun voltage of 6 kV.

  2. Collisionless Reconnection with Weak Slow Shocks Under Anisotropic MHD Approximation

    NASA Astrophysics Data System (ADS)

    Hirabayashi, K.; Hoshino, M.

    2014-12-01

    Magnetic reconnection accompanied by a pair of slow-mode shock waves, known as Petschek's theory, has been widely studied as an efficient mechanism to convert magnetically stored energy to thermal and/or kinetic energy in plasmas. Satellite observations in the Earth's magnetotail, on the other hand, report that the detection of slow shocks is rare compared with the theory. As an important step to bridge the gap between the observational fact and the Petschek-type reconnection, we performed one- and two- dimensional collisionless magnetohydrodynamic (MHD) simulations of magnetic reconnection paying special attention to the effect of temperature anisotropy. In high-beta plasmas such as a plasma sheet in the magnetotail, it is expected that even weak temperature anisotropy can greatly modify the dynamics. We demonstrate that the slow shocks do exist in the reconnection layer even under the anisotropic temperature. The resultant shocks, however, are weaker than those in isotropic MHD in terms of plasma compression. In addition, the amount of magnetic energy released across the shock is extremely small, that is, the shock is no longer switch-off type. In spite of the weakness of the shocks, the reconnection rates measured by the inflow velocities are kept at the same level as the isotropic cases. Once the slow shock forms, the downstream plasma is heated in highly anisotropic manner, and the firehose-sense anisotropy affects the wave structure in the system. In particular, it is remarkable that the sequential order of propagation of slow shocks and rotational discontinuities reverses depending upon the magnitude of a superposed guide field. Our result is consistent with the rareness of the slow shock detection in the magnetotail, and implies that shocks do not necessarily play an important role. Furthermore, a variety of wave structure of a reconnection layer shown here will help interpretation of observational data in collisionless reconnection.

  3. Dynamics of bulk electron heating and ionization in solid density plasmas driven by ultra-short relativistic laser pulses

    NASA Astrophysics Data System (ADS)

    Huang, L. G.; Kluge, T.; Cowan, T. E.

    2016-06-01

    The dynamics of bulk heating and ionization is investigated both in simulations and theory, which determines the crucial plasma parameters such as plasma temperature and density in ultra-short relativistic laser-solid target interactions. During laser-plasma interactions, the solid density plasma absorbs a fraction of laser energy and converts it into kinetic energy of electrons. A portion of the electrons with relativistic kinetic energy goes through the solid density plasma and transfers energy into the bulk electrons, which results in bulk electron heating. The bulk electron heating is finally translated into the processes of bulk collisional ionization inside the solid target. A simple model based on the Ohmic heating mechanism indicates that the local and temporal profile of bulk return current is essential to determine the temporal evolution of bulk electron temperature. A series of particle-in-cell simulations showing the local heating model is robust in the cases of target with a preplasma and without a preplasma. Predicting the bulk electron heating is then benefit for understanding the collisional ionization dynamics inside the solid targets. The connection of the heating and ionization inside the solid target is further studied using Thomas-Fermi model.

  4. Fusion reactivity, confinement, and stability of neutral-beam heated plasmas in TFTR and other tokamaks

    SciTech Connect

    Park, Hyeon, K.; Sabbagh, S.A.

    1996-05-01

    The hypothesis that the heating beam fueling profile shape connects the edge condition and improved core confinement and fusion reactivity is extensively studied on TFTR and applied to other tokamaks. The derived absolute scalings based on beam fueling profile shape for the stored energy and neutron yield can be applied to the deuterium discharges at different major radii in TFTR. These include Supershot, High poloidal beta, L-mode, and discharges with a reversed shear (RS) magnetic configuration. These scalings are also applied to deuterium-tritium discharges. The role of plasma parameters, such as plasma current, Isdo2(p), edge safety factor, qsdo5(a), and toroidal field, Bsdo2(T), in the performance and stability of the discharges is explicitly studied. Based on practical and externally controllable plasma parameters, the limitation and optimization of fusion power production of the present TFTR is investigated and a path for a discharge condition with fusion power gain, Q > 1 is suggested based on this study. Similar physics interpretation is provided for beam heated discharges on other major tokamaks.

  5. High Heat Flux Interactions and Tritium Removal from Plasma Facing Components by a Scanning Laser

    SciTech Connect

    C.H. Skinner; C.A. Gentile; A. Hassanein

    2002-01-28

    A new technique for studying high heat flux interactions with plasma facing components is presented. The beam from a continuous wave 300 W neodymium laser was focused to 80 W/mm2 and scanned at high speed over the surface of carbon tiles. These tiles were previously used in the TFTR [Tokamak Fusion Test Reactor] inner limiter and have a surface layer of amorphous hydrogenated carbon that was codeposited during plasma operations. Laser scanning released up to 84% of the codeposited tritium. The temperature rise of the codeposit on the tiles was significantly higher than that of the manufactured material. In one experiment, the codeposit surface temperature rose to 1,770 C while for the same conditions, the manufactured surface increased to only 1,080 C. The peak temperature did not follow the usual square-root dependence on heat pulse duration. Durations of order 100 ms resulted in brittle destruction and material loss from the surface, while a duration of approximately 10 ms showed minimal change. A digital microscope imaged the codeposit before, during, and after the interaction with the laser and revealed hot spots on a 100-micron scale. These results will be compared to analytic modeling and are relevant to the response of plasma facing components to disruptions and vertical displacement events (VDEs) in next-step magnetic fusion devices.

  6. RF Heating and Current Drive in Magnetically Confined Plasma: a Historical Perspective

    SciTech Connect

    Porkolab, Miklos

    2007-09-28

    The history of high power RF waves injected into magnetically confined plasma for the purposes of heating to fusion relevant temperatures spans nearly five decades. The road to success demanded the development of the theory of wave propagation in high temperature plasma in complex magnetic field geometries, development of antenna structures and transmission lines capable of handling high RF powers, and the development of high power RF (microwave) sources. In the early days, progress was hindered by the lack of good confinement of energetic particles formed by high power RF wave-plasma interactions. For example, in the ion cyclotron resonance frequency regime (ICRF) ions with energies in the multi-100keV, or even MeV range may be formed due to the presence of efficient 'minority species' absorption. Electrons with similar energies can be formed upon the injection of RF waves in the electron cyclotron resonance (ECRH) or lower hybrid range of frequencies (LHRF) because of quasi-linear Landau (cyclotron) interactions between waves and particles. In this paper a summary of four decades of historical evolution of wave heating and current drive results will be given.

  7. Propagation of a laser beam in a time-varying waveguide. [plasma heating for controlled fusion

    NASA Technical Reports Server (NTRS)

    Chapman, J. M.; Kevorkian, J.

    1978-01-01

    The propagation of an axisymmetric laser beam in a plasma column having a radially parabolic electron density distribution is reported. For the case of an axially uniform waveguide it is found that the basic characteristics of alternating focusing and defocusing beams are maintained. However, the intensity distribution is changed at the foci and outer-beam regions. The features of paraxial beam propagation are discussed with reference to axially varying waveguides. Laser plasma coupling is considered noting the case where laser heating produces a density distribution radially parabolic near the axis and the energy absorbed over the focal length of the plasma is small. It is found that: (1) beam-propagation stability is governed by the relative magnitude of the density fluctuations existing in the axial variation of the waveguides due to laser heating, and (2) for beam propagation in a time-varying waveguide, the global instability of the propagation is a function of the initial fluctuation growth rate as compared to the initial time rate of change in the radial curvature of the waveguide.

  8. Gas and heat dynamics of a micro-scaled atmospheric pressure plasma reference jet

    NASA Astrophysics Data System (ADS)

    Kelly, Seán; Golda, Judith; Turner, Miles M.; Schulz-von der Gathen, Volker

    2015-11-01

    Gas and heat dynamics of the ‘Cooperation on Science and Technology (COST) Reference Microplasma Jet’ (COST-jet), a European lead reference device for low temperature atmospheric pressure plasma application, are investigated. Of particular interest to many biomedical application scenarios, the temperature characteristics of a surface impacted by the jet are revealed. Schlieren imaging, thermocouple measurements, infrared thermal imaging and numerical modelling are employed. Temperature spatial profiles in the gas domain reveal heating primarily of the helium fraction of the gas mixture. Thermocouple and model temporal data show a bounded exponential temperature growth described by a single characteristic time parameter to reach  ∼63% or (1-1/e) fraction of the temperature increase. Peak temperatures occurred in the gas domain where the carrier jet exits the COST-jet, with values ranging from ambient temperatures to in excess of 100 °C in ‘α-mode’ operation. In a horizontal orientation of the COST-jet a curved trajectory of the helium effluent at low gas flows results from buoyant forces. Gas mixture profiles reveal significant containment of the helium concentrations for a surface placed in close proximity to the COST-jet. Surface heating of a quartz plate follows a similar bounded exponential temporal temperature growth as device heating. Spatial profiles of surface heating are found to correlate strongly to the impacting effluent where peak temperatures occur in regions of maximum surface helium concentration.

  9. Streaked optical pyrometer for measuring surface temperature of ion heated plasma

    NASA Astrophysics Data System (ADS)

    Roycroft, R.; Dyer, G. M.; Wagner, C.; Bernstein, A.; Ditmire, T.; Hegelich, B. M.; Albright, B. J.; Fernandez, J. C.; Bang, W.; Bradley, P. A.; Gautier, D. C.; Hamilton, C. E.; Palaniyappan, S.; Santiago Cordoba, M. A.; Vold, E. L.; Yin, L.

    2015-11-01

    The evolution of the interface between a light and heavy material isochorically heated to warm dense matter conditions is important to the understanding of electrostatic effects on the usual hydrodynamic understanding of fluid mixing. In recent experiments at the Trident laser facility in Los Alamos National Laboratory, the target, containing a high Z and a low Z material, is heated to several eV by laser accelerated aluminum ions. We fielded a streaked optical pyrometer to measure surface temperature. The pyrometer images the back surface of a heated target on a sub-nanosecond timescale with 400nm light from the plasma. This poster presents the details of the experimental setup and pyrometer design, as well as initial results of ion heating of aluminum targets. The interface between heated diamond and gold is also observed. Work supported by NNSA cooperative agreement DE-NA0002008 and the Los Alamos National Laboratory Directed Research and Development Program under the auspices of the U.S. DOE NNSAS, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396.

  10. Local electron heating in the Io plasma torus associated with Io: the HISAKI observation

    NASA Astrophysics Data System (ADS)

    Tsuchiya, F.; Yoshioka, K.; Kimura, T.; Murakami, G.; Kagitani, M.; Yamazaki, A.; Kasaba, Y.; Sakanoi, T.; Yoshikawa, I.; Nozawa, H.

    2014-12-01

    Io-correlated brightness change in Io plasma torus (IPT) has been discovered by Voyager and show an evidence of local electron heating around Io. However, the amount of observation data is still limited to investigate its detail properties. In addition, the clear Io-correlated change has not been detected by EUVE and Cassini observations. Cause of the Io-correlated effect is still open issue. The HISAKI satellite was launched on Sep. 14, 2013 and started observation of IPT and Jovian aurora for more than two months since the end of Dec. 2013. EUV spectrograph onboard the HISAKI satellite covers wavelength range from 55 to 145 nm, a wide slit which had a field of view of 400 x 140 arc-second was chosen to measure radial distribution and time variation of IPT. Observation of IPT with HISAKI showed clear Io-correlated brightness change since the Voyager observation. The amplitude of the periodic variation associated with Io's orbital period was found. It also showed long-term variation during the HISAKI's observation period. Through the observation period, the amplitude was larger in the short wavelength than in long wavelength. The wavelength dependence suggests significant electron heating and/or hot electron production. The Io phase dependence shows that bright region is located just downstream of Io. These are evidence of local electron heating around/downstream of Io and consistent with the Voyager result. The brightness also depends on system-III longitude and has local maximum around 120 and 300 degrees. Based on an empirical model of IPT, electron density at Io also shows maxima around the same longitudes. This suggests that the electron heating process is related with plasma density at Io. Candidate mechanisms which are responsible for the electron heating will be discussed.

  11. Prediction of critical heat flux in water-cooled plasma facing components using computational fluid dynamics.

    SciTech Connect

    Bullock, James H.; Youchison, Dennis Lee; Ulrickson, Michael Andrew

    2010-11-01

    Several commercial computational fluid dynamics (CFD) codes now have the capability to analyze Eulerian two-phase flow using the Rohsenow nucleate boiling model. Analysis of boiling due to one-sided heating in plasma facing components (pfcs) is now receiving attention during the design of water-cooled first wall panels for ITER that may encounter heat fluxes as high as 5 MW/m2. Empirical thermalhydraulic design correlations developed for long fission reactor channels are not reliable when applied to pfcs because fully developed flow conditions seldom exist. Star-CCM+ is one of the commercial CFD codes that can model two-phase flows. Like others, it implements the RPI model for nucleate boiling, but it also seamlessly transitions to a volume-of-fluid model for film boiling. By benchmarking the results of our 3d models against recent experiments on critical heat flux for both smooth rectangular channels and hypervapotrons, we determined the six unique input parameters that accurately characterize the boiling physics for ITER flow conditions under a wide range of absorbed heat flux. We can now exploit this capability to predict the onset of critical heat flux in these components. In addition, the results clearly illustrate the production and transport of vapor and its effect on heat transfer in pfcs from nucleate boiling through transition to film boiling. This article describes the boiling physics implemented in CCM+ and compares the computational results to the benchmark experiments carried out independently in the United States and Russia. Temperature distributions agreed to within 10 C for a wide range of heat fluxes from 3 MW/m2 to 10 MW/m2 and flow velocities from 1 m/s to 10 m/s in these devices. Although the analysis is incapable of capturing the stochastic nature of critical heat flux (i.e., time and location may depend on a local materials defect or turbulence phenomenon), it is highly reliable in determining the heat flux where boiling instabilities begin

  12. Impact of the background toroidal rotation on particle and heat turbulent transport in tokamak plasmas

    SciTech Connect

    Camenen, Y.; Peeters, A. G.; Casson, F. J.; Hornsby, W. A.; Snodin, A. P.; Angioni, C.; Strintzi, D.

    2009-01-15

    Recent developments in the gyrokinetic theory have shown that, in a toroidal device, the Coriolis drift associated with the background plasma rotation significantly affects the small scale instabilities [A. G. Peeters et al., Phys. Rev. Lett. 98, 265003 (2007)]. The later study, which focuses on the effect of the Coriolis drift on toroidal momentum transport is extended in the present paper to heat and particle transport. It is shown numerically using the gyrokinetic flux-tube code GKW[A. G. Peeters and D. Strintzi, Phys. Plasmas 11, 3748 (2004)], and supported analytically, that the Coriolis drift and the parallel dynamics play a similar role in the coupling of density, temperature, and velocity perturbations. The effect on particle and heat fluxes increases with the toroidal rotation (directly) and with the toroidal rotation gradient (through the parallel mode structure), depends on the direction of propagation of the perturbation, increases with the impurity charge number and with the impurity mass to charge number ratio. The case of very high toroidal rotation, relevant to spherical tokamaks, is investigated by including the effect of the centrifugal force in a fluid model. The main effect of the centrifugal force is to decrease the local density gradient at the low field side midplane and to add an extra contribution to the fluxes. The conditions for which the inertial terms significantly affect the heat and particle fluxes are evidenced.

  13. Coronal heating driven by a magnetic gradient pumping mechanism in solar plasmas

    SciTech Connect

    Tan, Baolin

    2014-11-10

    The heating of the solar corona is a longstanding mystery in astrophysics. Considering that the solar magnetic field is spatially inhomogeneous with a considerable magnetic gradient from the solar surface to the corona, this work proposes a magnetic gradient pumping (MGP) mechanism to try to explain the formation of hot plasma upflows, such as hot type II spicules and hot plasma ejections. In the MGP mechanism, the magnetic gradient may drive the energetic particles to move upward from the underlying solar atmosphere and form hot upflows. These upflow energetic particles are deposited in the corona, causing it to become very hot. Rough estimations indicate that the solar corona can be heated to above 1 million degrees, and the upflow velocity is about 40 km s{sup –1} in the chromosphere and about 130 km s{sup –1} in the corona. The solar magnetic flux tubes act as pumpers to extract energetic particles from the underlying thermal photosphere, convey them, and deposit them in the corona. The deposit of these energetic particles causes the corona to become hot, and the escape of such particles from the photosphere leaves it a bit cold. This mechanism can present a natural explanation to the mystery of solar coronal heating.

  14. Plasma catecholamines and hyperglycaemia influence thermoregulation in man during prolonged exercise in the heat.

    PubMed

    Mora-Rodríguez, R; González-Alonso, J; Below, P R; Coyle, E F

    1996-03-01

    1. We manipulated plasma catecholamines (combined adrenaline and noradrenaline concentrations) to three levels during prolonged exercise to determine their effect on cutaneous and forearm vascular conductance (CVC and FVC), oesophageal temperature (T(oes)) and cardiovascular responses. 2. On three occasions, seven endurance-trained men cycled at 65% VO2, max in the heat (33.1 +/- 0.7 degrees C) for 120-150 min. During the control trial (150 min duration), 0.45% saline was intravenously infused (SI) starting at 30 min, at a rate that replaced a third of the fluid losses. The infusion start time and rate were identical in all three trials. During SI, plasma catecholamine levels increased progressively and were 18.2 +/- 2.7 pmol ml-1 at 150 min. In another trial (120 min duration), adrenaline was infused (AI) at 0.1 microgram kg-1 min-1 and plasma catecholamine levels were elevated 6 pmol ml-1 above SI during the 60-120 min period. In a third trial (150 min duration), an 18% glucose solution was infused (GI) at a rate that maintained plasma glucose levels above 11 mM and plasma catecholamine levels were 5.0-5.5 pmol ml-1 lower (P < 0.05) than SI from 120-150 min. 3. Heat production and sweat rate were not different during the three trials and neither was the decline in stroke volume, cardiac output and mean arterial pressure. 4. Soon after beginning AI, CVC decreased 15%, T(oes) increased by 0.4 +/- 0.1 degree C and heart rate increased by 6 +/- 1 beats min-1; these significant (P < 0.05) differences from SI were maintained throughout the bout. As a result of GI, FVC was 15% higher than SI and T(oes) and heart rate were attenuated by 0.3 +/- 0.1 degree C and 7 +/- 1 beats min-1 at 150 min compared with SI (P < 0.05). 5. In conclusion, large increases in plasma catecholamine levels cause hyperthermia during exercise by vasoconstricting the skin. The mechanisms by which hyperglycaemia (i.e. 11 mM) attenuates hyperthermia are less clear and may be due to others factors

  15. Behavior of graphite under heat load and in contact with a hydrogen plasma

    NASA Astrophysics Data System (ADS)

    Bohdansky, J.; Croessmann, C. D.; Linke, J.; McDonald, J. M.; Morse, D. H.; Pontau, A. E.; Watson, R. D.; Whitley, J. B.; Goebel, D. M.; Hirooka, Y.; Leung, K.; Conn, R. W.; Roth, J.; Ottenberger, W.; Kotzlowski, H. E.

    1987-05-01

    Graphite is extensively used in large tokamaks today. In these machines the material is exposed to vacuum, to intense heat loads, and to the edge plasma. The use of graphite in such machines, therefore, depends on the outgassing behavior, the heat shock resistance, and thermochemical properties in a hydrogen plasma. Investigations of these properties made at different laboratories are described here. Experiments conducted at Sandia National Laboratories (SNL), Livermore, and the Max-Planck-Institut für Plasmaphysik (IPP) in Garching showed that the outgassing behavior of fine-grain reactor-grade graphite and carbon fiber composites depends on the pretreatment (manufacturing and/or storage). However, after proper outgassing the samples tested behave similarly in the case of fine-grain graphite, but the outgassing remains high for the carbon fiber composites. Heat shock tests have been made with the Electron Beam Test System (EBTS) at SNL, Albuquerque. Directly cooled graphite samples (FE 159 graphite brazed onto Mo tubes) showed no failure at a heat load of 700 W/cm 2, 20 s; or 10 kW, 1 s. Thermal erosion due to sublimination and particle emission from the graphite surface was observed. This effect is related to the surface temperature and becomes significant at temperatures above 2500°K. Fourteen different types of graphite were tested; the main differences among these samples were the different surface temperatures obtained under the same heating conditions. Cracking due to heat shocks was observed in some of the samples, but none of the carbon fiber composites failed. Thermochemical properties have been tested in the PISCES plasma generator at UCLA for ion energies of around 100 eV. The formation of C-H compounds was observed spectroscopically at sample temperatures of around 600°C. However, this chemical reaction did not lead to erosion as observed in beam experiments but to a drastic change of the surface structure due to redeposition. Carbon-hydrogen lines

  16. An overview of the VASIMR engine: High power space propulsion with RF plasma generation and heating

    NASA Astrophysics Data System (ADS)

    Díaz, F. R. Chang

    2001-10-01

    The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) is a high power, radio frequency-driven magnetoplasma rocket, capable of exhaust modulation at constant power. While the plasma is produced by a helicon discharge, the bulk of the energy is added in a separate downstream stage by ion cyclotron resonance heating (ICRH). Axial momentum is obtained by the adiabatic expansion of the plasma in a magnetic nozzle. Exhaust variation in the VASIMR is primarily achieved by the selective partitioning of the RF power to the helicon and ICRH systems, with the proper adjustment of the propellant flow. However, other complementary techniques are also being studied. Operational and performance considerations favor the light gases. The physics and engineering of this device have been under study since the late 1970s. A NASA-led, research effort, involving several terms in the United States, continues to explore the scientific and technological foundations of this concept. The research involves theory, experiment, engineering design, mission analysis, and technology development. Experimentally, high density, stable plasma discharges have been generated in Helium, Hydrogen and Deuterium, as well as mixtures of these gases. Key issues involve the optimization of the helicon discharge for high-density operation and the efficient coupling of ICRH to the plasma, prior to acceleration by the magnetic nozzle. Theoretically, the dynamics of the magnetized plasma are being studied from kinetic and fluid perspectives. Plasma acceleration by the magnetic nozzle and subsequent detachment has been demonstrated in numerical simulations. These results are presently undergoing experimental verification. A brisk technology development effort for space-qualified, compact, solid-state RF equipment, and high temperature superconducting magnets is under way in support of this project. A conceptual point design for an early space demonstrator on the International Space Station has been defined

  17. Documentation and verification of VST2D; a model for simulating transient, Variably Saturated, coupled water-heat-solute Transport in heterogeneous, anisotropic 2-Dimensional, ground-water systems with variable fluid density

    USGS Publications Warehouse

    Friedel, Michael J.

    2001-01-01

    This report describes a model for simulating transient, Variably Saturated, coupled water-heatsolute Transport in heterogeneous, anisotropic, 2-Dimensional, ground-water systems with variable fluid density (VST2D). VST2D was developed to help understand the effects of natural and anthropogenic factors on quantity and quality of variably saturated ground-water systems. The model solves simultaneously for one or more dependent variables (pressure, temperature, and concentration) at nodes in a horizontal or vertical mesh using a quasi-linearized general minimum residual method. This approach enhances computational speed beyond the speed of a sequential approach. Heterogeneous and anisotropic conditions are implemented locally using individual element property descriptions. This implementation allows local principal directions to differ among elements and from the global solution domain coordinates. Boundary conditions can include time-varying pressure head (or moisture content), heat, and/or concentration; fluxes distributed along domain boundaries and/or at internal node points; and/or convective moisture, heat, and solute fluxes along the domain boundaries; and/or unit hydraulic gradient along domain boundaries. Other model features include temperature and concentration dependent density (liquid and vapor) and viscosity, sorption and/or decay of a solute, and capability to determine moisture content beyond residual to zero. These features are described in the documentation together with development of the governing equations, application of the finite-element formulation (using the Galerkin approach), solution procedure, mass and energy balance considerations, input requirements, and output options. The VST2D model was verified, and results included solutions for problems of water transport under isohaline and isothermal conditions, heat transport under isobaric and isohaline conditions, solute transport under isobaric and isothermal conditions, and coupled water-heat

  18. Heating of thermal helium in the equatorial magnetosphere - A simulation study

    NASA Technical Reports Server (NTRS)

    Omura, Y.; Ashour-Abdalla, M.; Gendrin, R.; Quest, K.

    1985-01-01

    The heating of He(+) ions observed by the GEOS satellite at L of about seven starting from an initial anisotropic proton distribution is studied. A simulation of electromagnetic ion cyclotron waves in a plasma consisting of hot anisotropic protons, a dominant thermal hydrogen plasma, and a minority species of helium ions is utilized. It is shown that the thermal ions are heated to 100 times their initial temperature due to the growth of large-amplitude ion cyclotron waves. He(+) ions are heated mainly in the perpendicular direction, and they are heated more than cold H(+) ions. The He(+) ions are heated in a two-step process. First, they are set into oscillations by the growing wave until some of the ions reach a parallel velocity on the order of the resonant velocity; then, strong heating occurs.

  19. Application of Laser-Generated Ion Beams for Isochoric Heating to Study Plasma Mix at Interfaces

    NASA Astrophysics Data System (ADS)

    Albright, B. J.; Fernández, J. C.; Bang, W.; Bradley, P. A.; Gautier, D. C.; Hamilton, C. E.; Palaniyappan, S.; Santiago Cordoba, M. A.; Vold, E. L.; Yin, L.; Hegelich, B. M.; Dyer, G.; Roycroft, R.

    2015-11-01

    The evolution and mixing of high-Z/low-Z interfaces in plasma media is of profound importance to high energy density physics and inertial fusion experiments. Recent experiments performed at the LANL Trident laser facility as part of the Plasma Interfacial Mix project have applied novel, laser-generated ion beams created under conditions of relativistic induced transparency to the heating of solid-density, multi-material targets isochorically and uniformly (over a few tens of ps), attaining plasma temperatures of several eV. Measurements have been made of the evolving plasma, including location of the material interface and the time-history of the temperature of the medium. Recent data and associated radiation hydrodynamic modeling from our Trident campaigns will be reported. Complementary kinetic simulations of interface evolution, showing anomalously rapid atomic mixing under conditions relevant to ICF experiments, will also be discussed. Work performed under the auspices of the U.S. DOE by the LANS, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396. Funding provided by the Los Alamos National Laboratory Directed Research and Development Program.

  20. Plasma Heating and Current Drive by Stochastic Acceleration of Relativistic Electrons at the WEGA Stellarator

    NASA Astrophysics Data System (ADS)

    Laqua, Heinrich; Chlechowitz, Enrico; Fuchs, Vladimir; Otte, Matthias; Stange, Torsten

    2013-10-01

    Relativistic electrons with parallel energies of up to 2 MeV have been continuously (10 s) generated by a stochastic interaction with the rf-field (6-26kW) of a 2.45 GHz open waveguide antenna without any loop voltage. These ``run-away'' electrons have been detected by their synchrotron, x- and γ-ray emission and have also generated a toroidal plasma current in the kA range. They are perfectly confined in the stellarator magnetic field of 0.5 T. The particle trajectories form their own nested drift surfaces which are shrunken inward and shifted outward with respect to the magnetic flux surfaces. This geometrical effect connects the antenna region, where the electrons are accelerated, with the plasma core, where a low temperature (20eV, 0.2-5 1018m3) bulk plasma is generated. The acceleration process was modelled by a random walk diffusion model and a Fermi Ulan map Monte-Carlo simulation. Both calculations show similar results for the heating and current drive efficiencies. They also reproduce the temporal behaviour of the plasma current and the synchrotron radiation, when the RF-power is modulated and show the need for a random phase interaction between the relativistic electrons and the antenna field.

  1. Turbulent transport and heating in the auroral plasma of the topside ionosphere

    NASA Technical Reports Server (NTRS)

    Ionson, J. A.; Ong, R. S. B.; Fontheim, E. G.

    1979-01-01

    Using plasma parameters from a typical stormtime ionospheric energy balance model, we have investigated the effects of plasma turbulence on the auroral magnetoplasma. The turbulence is assumed to be comprised of electrostatic ion cyclotron waves. These waves have been driven to a nonthermal level by a geomagnetic field-aligned, current-driven instability. The evolution of this instability is shown to proceed in two stages and indicates an anomalous increase in field-aligned electrical resistivity and cross-field ion thermal conductivity as well as a decrease in electron thermal conductivity along the geomagnetic field. In addition, this turbulence heats ions perpendicular to the geomagnetic field and hence leads to a significant ion temperature anisotropy.

  2. Microwave heating power distribution in electron-cyclotron resonance processing plasmas, experiment and theory

    SciTech Connect

    Douglass, S.R.; Eddy, C. Jr.; Lampe, M.; Joyce, G.; Slinker, S.; Weber, B.V.

    1995-12-31

    The authors are currently investigating the mechanisms of microwave power absorption in an ECR plasma. The microwave electric field is detected with an antenna at the end of a shielded co-ax cable, connected to a bolometer for power measurements. Initial measurements have been 1-D along the axis of the plasma chamber. Later, 3-D profiles will be made of the microwave heating power distribution. A comparison of the experimental results with the theoretical microwave absorption are presented. A ray tracing analysis of the propagating right hand wave are given, including both collisional and collisionless absorption. Mode conversion effects are studied to explain why most of the power is absorbed at the entry window, especially the L wave power.

  3. MW-scale ICRF plasma heating using IGBT switches in a multi-pulse scheme

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    Solid-state silicon switches are cheap and reliable option for 1-10 MHz RF power sources, required for plasma ion cyclotron RF heating (ICRF). The large `on' resistance of MOSFET and similar devices limits their power delivery to a few tens of kW per switch. Low resistivity devices, such as IGBT, suffer from large `off' switching time, which limits their useful frequency range and increases the power dissipated in the switch. Here we demonstrate more than 0.8 MW circulated RF power at 2 MHz using only three high voltage IGBT switches. The circuit uses the fast `on' switching capability of the IGBTs to generate high-Q pulse train. This operation mode also simplifies the measurement of RF coupling between the antenna and the plasma.

  4. Magnetic flux and heat losses by diffusive, advective, and Nernst effects in MagLIF-like plasma

    SciTech Connect

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

    2014-12-15

    The MagLIF approach to inertial confinement fusion involves subsonic/isobaric compression and heating of a DT 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 plasma to the cold liner is dominated by the 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} effective diffusion coefficients determining the losses of heat and magnetic flux are both shown to decrease with ω{sub e}τ{sub e} as does the Bohm diffusion coefficient, which is commonly associated with low collisionality and two-dimensional transport. This family of exact solutions can be used for verification of codes that model the MagLIF plasma dynamics.

  5. Magnetic flux and heat losses by diffusive, advective, and Nernst effects in MagLIF-like plasma

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The MagLIF approach to inertial confinement fusion involves subsonic/isobaric compression and heating of a DT 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 plasma to the cold liner is dominated by the 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 effective diffusion coefficients determining the losses of heat and magnetic flux are both shown to decrease with ωeτe as does the Bohm diffusion coefficient, which is commonly associated with low collisionality and two-dimensional transport. This family of exact solutions can be used for verification of codes that model the MagLIF plasma dynamics.

  6. Fractionation of outdated freeze-dried plasma: a comparative study of cold- and heat-ethanol fractionation procedures.

    PubMed

    Schneider, W; Wolter, D; Shapiro, M; McCarty, L

    1979-01-01

    In a comparative study a total volume of 1435 kg outdated freeze-dried plasma, equivalent to approx. 200,000 kg liquid plasma, was fractionated into albumin (20%): about 30% of the total plasma volume was fractionated following the cold-ethanol procedure and about 70% following the heat-ethanol method. Average albumin recovery following cold-ethanol preparation was 47% of the albumin originally present in the freeze-dried plasma (= 50% of total protein); following heat-ethanol fractionation, 71%. Gelfiltration of heat-ethanol albumin showed a main peak (= 93%) representing albumin monomers and one slightly faster component (= 7%) representing albumin dimers. Gelfiltration of cold-ethanol isolated albumin on the other hand showed four peaks: albumin monomers (= 60%), albumin dimers (= 15%), and two other peaks representing higher molecular weight molecules (= 25%). Hemoglobin present in the reconstituted plasma was reduced about five-fold in the cold-ethanol product and about ten-fold in the heat-ethanol albumin. Stability tests of both products did not differ from equivalent products isolated from normal human plasma. Besides albumin, immunoglobulins may be isolated as Cohn fraction II-III prior to the heating procedure without significant albumin loss. PMID:88384

  7. Impact of combined transient plasma/heat loads on tungsten performance below and above recrystallization temperature

    NASA Astrophysics Data System (ADS)

    Loewenhoff, Th.; Bardin, S.; Greuner, H.; Linke, J.; Maier, H.; Morgan, T. W.; Pintsuk, G.; Pitts, R. A.; Riccardi, B.; De Temmerman, G.

    2015-11-01

    The influence of recrystallization on thermal shock resistance has been identified as an issue that may influence the long term performance of ITER tungsten (W) divertor components. To investigate this issue a unique series of experiments has been performed on ITER divertor W monoblock mock-ups in three EU high heat flux facilities: GLADIS (neutral beam), JUDITH 2 (electron beam) and Magnum-PSI (plasma beam). To simulate ITER mitigated edge localised modes, heat fluxes between 0.11 and 0.6 GW m-2 were applied for Δt  <  1 ms. Two different base temperatures, Tbase  =  1200 °C and 1500 °C, were chosen on which ~18 000/100 000 transient events were superimposed representing several full ITER burning plasma discharges in terms of number of transients and particle fluence. An increase in roughening for both e-beam and plasma loaded surfaces was observed when loading during or after recrystallization and when loading at higher temperature. However, regarding the formation of cracks and microstructural modifications the response was different for e-beam and plasma loaded surfaces. The samples loaded in Magnum-PSI did not crack nor show any sign of recrystallization, even at Tbase  =  1500 °C. This could be a dynamic hydrogen flux effect, because pre-loading of samples with hydrogen neutrals (GLADIS) or without hydrogen (e-beam JUDITH 2) did not yield this result. These results show clearly that the loading method used when investigating and qualifying the thermal shock performance of materials for ITER and future fusion reactors can play an important role. This should be properly accounted for and in fact should be the subject of further R&D.

  8. A new ion cyclotron range of frequency scenario for bulk ion heating in deuterium-tritium plasmas: How to utilize intrinsic impurities in our favour

    NASA Astrophysics Data System (ADS)

    Kazakov, Ye. O.; Ongena, J.; Van Eester, D.; Bilato, R.; Dumont, R.; Lerche, E.; Mantsinen, M.; Messiaen, A.

    2015-08-01

    A fusion reactor requires plasma pre-heating before the rate of deuterium-tritium fusion reactions becomes significant. In ITER, radio frequency (RF) heating of 3He ions, additionally puffed into the plasma, is one of the main options considered for increasing bulk ion temperature during the ramp-up phase of the pulse. In this paper, we propose an alternative scenario for bulk ion heating with RF waves, which requires no extra 3He puff and profits from the presence of intrinsic Beryllium impurities in the plasma. The discussed method to heat Be impurities in D-T plasmas is shown to provide an even larger fraction of fuel ion heating.

  9. Electronic excitation as a mode of heat dissipation in laser-driven cluster plasmas

    SciTech Connect

    Rajeev, R.; Rishad, K. P. M.; Madhu Trivikram, T.; Krishnamurthy, M.

    2013-12-15

    Electrons streaming out of laser plasma are known for non-local heat transport and energy deposition by the ionization wave. At 100 eV electron temperature, since the electronic excitation cross section is comparable to that of ionization for Ar and CO{sub 2}, a non-local excitation wave akin to the ionization wave is envisaged where energy deposition in excitations forms a excited cluster sheath beyond the laser focus. Here, we show that nano-cluster systems have the right parameters to form such an exciton sheath and experimentally demonstrate this via charge transfer reactions.

  10. Impact excitation of neon atoms by heated seed electrons in filamentary plasma gratings.

    PubMed

    Shi, Liping; Li, Wenxue; Zhou, Hui; Ding, Liang'en; Zeng, Heping

    2013-02-15

    We demonstrate impact ionization and dissociative recombination of neon (Ne) atoms by means of seeded-electron heating and subsequent electron-atom collisions in an ultraviolet plasma grating, allowing for a substantial fraction of the neutral Ne atomic population to reside in high-lying excited states. A buffer gas with relatively low ionization potential (nitrogen or argon) was used to provide high-density seed electrons. A three-step excitation model is verified by the fluorescence emission from the impact excitation of Ne atoms. PMID:23455081

  11. Quantum Efficiency and Topography of Heated and Plasma-Cleaned Copper Photocathode Surfaces

    SciTech Connect

    Palmer, Dennis T.; Kirby, R.E.; King, F.K.; /SLAC

    2005-08-04

    We present measurements of photoemission quantum efficiency (QE) for copper photocathodes heated and cleaned by low energy argon and hydrogen ion plasma. The QE and surface roughness parameters were measured before and after processing and surface chemical composition was tracked in-situ with x-ray photoelectron spectroscopy (XPS). Thermal annealing at 230 C was sufficient to improve the QE by 3-4 orders of magnitude, depending on the initial QE. Exposure to residual gas slowly reduced the QE but it was easily restored by argon ion cleaning for a few minutes. XPS showed that the annealing or ion bombardment removed surface water and hydrocarbons.

  12. Structure of intermediate shocks and slow shocks in a magnetized plasma with heat conduction

    SciTech Connect

    Tsai, C.L.; Wu, B.H.; Lee, L.C.

    2005-08-15

    The structure of slow shocks and intermediate shocks in the presence of a heat conduction parallel to the local magnetic field is simulated from the set of magnetohydrodynamic equations. This study is an extension of an earlier work [C. L. Tsai, R. H. Tsai, B. H. Wu, and L. C. Lee, Phys. Plasmas 9, 1185 (2002)], in which the effects of heat conduction are examined for the case that the tangential magnetic fields on the two side of initial current sheet are exactly antiparallel (B{sub y}=0). For the B{sub y}=0 case, a pair of slow shocks is formed as the result of evolution of the initial current sheet, and each slow shock consists of two parts: the isothermal main shock and the foreshock. In the present paper, cases with B{sub y}{ne}0 are also considered, in which the evolution process leads to the presence of an additional pair of time-dependent intermediate shocks (TDISs). Across the main shock of the slow shock, jumps in plasma density, velocity, and magnetic field are significant, but the temperature is continuous. The plasma density downstream of the main shock decreases with time, while the downstream temperature increases with time, keeping the downstream pressure constant. The foreshock is featured by a smooth temperature variation and is formed due to the heat flow from downstream to upstream region. In contrast to the earlier study, the foreshock is found to reach a steady state with a constant width in the slow shock frame. In cases with B{sub y}{ne}0, the plasma density and pressure increase and the magnetic field decreases across TDIS. The TDIS initially can be embedded in the slow shock's foreshock structure, and then moves out of the foreshock region. With an increasing B{sub y}, the propagation speed of foreshock leading edge tends to decrease and the foreshock reaches its steady state at an earlier time. Both the pressure and temperature downstreams of the main shock decrease with increasing B{sub y}. The results can be applied to the shock heating

  13. Production of ultra clean gas-atomized powder by the plasma heated tundish technique

    SciTech Connect

    Tingskog, T.A.; Andersson, V.

    1996-12-31

    The paper describes the improvements in cleanliness for different types of gas atomized powders produced by holding the melt in a Plasma Heated Tundish (PHT) before atomization. The cleanliness is measured on Hot Isostatically Pressed (HIP) or extruded samples. Significant improvements in slag levels and material properties have been achieved. On extruded powder metallurgy stainless steel and nickel alloy tubes, the rejection rate in ultra-sonic testing was reduced drastically. Tool steels and high speed steels have greatly improved ductility and bend strength.

  14. Investigating the laser heating of underdense plasmas at conditions relevant to MagLIF

    NASA Astrophysics Data System (ADS)

    Harvey-Thompson, Adam

    2015-11-01

    The magnetized Liner Inertial Fusion (MagLIF) scheme has achieved thermonuclear fusion yields on Sandia's Z Facility by imploding a cylindrical liner filled with D2 fuel that is preheated with a multi-kJ laser and pre-magnetized with an axial field Bz = 10 T. The challenge of fuel preheating in MagLIF is to deposit several kJ's of energy into an underdense (ne/ncrit<0.1) fusion fuel over ~ 10 mm target length efficiently and without introducing contaminants that could contribute to unacceptable radiative losses during the implosion. Very little experimental work has previously been done to investigate laser heating of gas at densities, scale lengths, modest intensities (Iλ2 ~ 1014 watts- μm2 /cm2) and magnetization parameters (ωceτe ~ 10) necessary for MagLIF. In particular, magnetization of the preheated plasma suppresses electron thermal conduction, which can modify laser energy coupling. Providing an experimental dataset in this regime is essential to not only understand the dynamics of a MagLIF implosion and stagnation, but also to validate magnetized transport models and better understand the physics of laser propagation in magnetized plasmas. In this talk, we present data and analysis of several experiments conducted at OMEGA-EP and at Z to investigate laser propagation and plasma heating in underdense D2 plasmas under a range of conditions, including densities (ne = 0.05-0.1 nc) and magnetization parmaters (ωceτe ~ 0-10). The results show differences in the electron temperature of the heated plasma and the velocity of the laser burn wave with and without an applied magnetic field. We will show comparisons of these experimental results to 2D and 3D HYDRA simulations, which show that the effect of the magnetic field on the electron thermal conduction needs to be taken into account when modeling laser preheat. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the National Nuclear Security Administration

  15. In Situ Observations of Ion Scale Current Sheets and Associated Electron Heating in Turbulent Space Plasmas

    NASA Astrophysics Data System (ADS)

    Chasapis, A.; Retino, A.; Sahraoui, F.; Greco, A.; Vaivads, A.; Khotyaintsev, Y. V.; Sundkvist, D. J.; Canu, P.

    2014-12-01

    We present a statistical study of ion-scale current sheets in turbulent space plasma. The study was performed using in situ measurements from the Earth's magnetosheath downstream of the quasi-parallel shock. Intermittent structures were identified using the Partial Variance of Increments method. We studied the distribution of the identified structures as a function of their magnetic shear angle, the PVI index and the electron heating. The properties of the observed current sheets were different for high (>3) and low (<3) values of the PVI index. We observed a distinct population of high PVI (>3) structures that accounted for ~20% of the total. Those current sheets have high magnetic shear (>90 degrees) and were observed mostly in close proximity to the bow shock with their numbers reducing towards the magnetopause. Enhancement of the estimated electron temperature within these current sheets suggest that they are important for local electron heating and energy dissipation.

  16. High average power CW FELs (Free Electron Laser) for application to plasma heating: Designs and experiments

    SciTech Connect

    Booske, J.H.; Granatstein, V.L.; Radack, D.J.; Antonsen, T.M. Jr.; Bidwell, S.; Carmel, Y.; Destler, W.W.; Latham, P.E.; Levush, B.; Mayergoyz, I.D.; Zhang, Z.X. . Lab. for Plasma Research); Freund, H.P. )

    1989-01-01

    A short period wiggler (period {approximately} 1 cm), sheet beam FEL has been proposed as a low-cost source of high average power (1 MW) millimeter-wave radiation for plasma heating and space-based radar applications. Recent calculation and experiments have confirmed the feasibility of this concept in such critical areas as rf wall heating, intercepted beam ( body'') current, and high voltage (0.5 - 1 MV) sheet beam generation and propagation. Results of preliminary low-gain sheet beam FEL oscillator experiments using a field emission diode and pulse line accelerator have verified that lasing occurs at the predicted FEL frequency. Measured start oscillation currents also appear consistent with theoretical estimates. Finally, we consider the possibilities of using a short-period, superconducting planar wiggler for improved beam confinement, as well as access to the high gain, strong pump Compton regime with its potential for highly efficient FEL operation.

  17. Plasma adenosine triphosphate and heat shock protein 72 concentrations after aerobic and eccentric exercise.

    PubMed

    Ogawa, Kishiko; Seta, Ryosuke; Shimizu, Takahiko; Shinkai, Shoji; Calderwood, Stuart K; Nakazato, Koichi; Takahashi, Kazue

    2011-01-01

    The endolysosome pathway has been proposed for secretion of heat shock protein (Hsp)72 with a regulatory role for extracellular adenosine triphosphate (ATP). Here, we tested the hypothesis that extracellular ATP mediates the increase in plasma Hsp72 after exercise. We measured plasma ATP Hsp72, cathepsin D, norepinephrine, free fatty acid, glucose, and myoglobin in 8 healthy young males (mean +/- SE: age, 22.3 +/- 0.3 years; height, 171.4 +/- 0.8 cm; weight, 68.8 +/- 3.1 kg; body mass index, 23.5 +/- 1.1 kg/cm2; VO2 max, 44.1 +/- 3.8 mL/kg/min) before and at 0, 10, 30, and 60 min after aerobic exercise (cycling) and elbow flexor eccentric exercise. Subjects cycled for 60 min at 70-75% VO2 max (mean +/- SE; 157.4 +/- 6.9 W). Eccentric strength exercise consisted of flexing the elbow joint to 90 degrees with motion speed set at 30 degrees/sec at extension and 10 degrees/sec at flexion. Subjects performed 7 sets of 10 eccentric actions with a set interval of 60 sec. The motion range of the elbow joint was 90 degrees-180 degrees. Compared with the levels of Hsp72 and ATP in plasma after bicycle exercise, those after eccentric exercise did not change. A significant group x time interaction was not observed for Hsp72 or ATP in plasma. A significant correlation was found between Hsp72 and ATP in plasma (r=0.79, P<0.05), but not between Hsp72 and norepinephrine (r=0.64, P=0.09) after bicycle exercise. A significant correlation between ATP and norepinephrine in plasma was found (r=0.89 P<0.01). We used stepwise multiple-regression analysis to determine independent predictors of exercise-induced elevation of eHsp72. Candidate predictor variables for the stepwise multiple-regression analysis were time (Pre, Post, Post10, Post30, Post60), exercise type (aerobic, eccentric), ATP, cathepsin D, norepinephrine, epinephrine, glucose, and FFA. In the regression model for Hsp72 in plasma, increased ATP and glucose were the strongest predictors of increased Hsp72 (ATP: R2=0.213, beta

  18. Heat Transfer In Sub- And Supersonic Nonequilibrium Jets Of Carbon Dioxide Plasmas

    NASA Astrophysics Data System (ADS)

    Kolesnikov, A. F.; Gordeev, A. N.; Vasilevskii, S. A.

    2011-05-01

    Subsonic high-enthalpy carbon dioxide flows are realized by using the 100-kW high-frequency inductive plasmatron IPG-4 at the pressures 37 and 96 hPa and enthalpies 16.4 and 16.2MJ/kg. The free stream parameters of the subsonic equilibrium carbon dioxide flow are rebuilt through CFD modeling with use of the data for stagnation point heat flux to silver and stagnation pressure. At the above pressures and enthalpies the catalytic efficiencies of silica-based thermal protection tile coating and sintered SiC surface are predicted in the temperature range 1453 - 1480 K and 1426 - 1536 K correspondingly and compared with our previous data [1] (stagnation pressure 60 - 140hPa, surface temperature 1600 - 1630K) and with results of actinometry and optical emission spectroscopy techniques for O-atoms recombination on β-cristobalite [2] at pressure 2 hPa and surface temperature 1600 K. In general the pressure and temperature ranges for catalytic efficiencies for both materials are expanded and the new and previous data are found to be in good agreement. Supersonic under-expanded jets of carbon dioxide plasma are obtained by using sonic nozzles of different throat diameters (D = 30 and 16 mm). Stagnation point heat fluxes and pressures on water-cooled cylindrical 20-mm diameter model in supersonic carbon dioxide plasma flows are measured. Dependences of the stagnation point heat flux to water-cooled copper wall and stagnation pressure versus distance from exit of the sonic nozzle are obtained for different ground pressure in the test chamber. The maximum of heat flux of 840 W/cm2 and maximum stagnation pressure of 142 hPa are realized using the sonic nozzle with 16-mm throat diameter, gas mass flow rate of 4.6g/s and generator anode power of 72 kW.

  19. Simulation Studies of Plasma Heating and Nonlinear Evolutions of Electrostatic and Electromagnetic Instabilities in a Field-Aligned Counter-Streaming Plasma

    NASA Astrophysics Data System (ADS)

    Tsai, T.; Chang, C.; Lyu, L.

    2006-12-01

    Nonlinear evolutions of electrostatic (ES) and electromagnetic (EM) instabilities in a field-aligned counter- streaming plasma are studied by means of a full particle code simulation and a Vlasov simulation. Our simulation results show that field-aligned counter-streaming plasma can lead to fast growing electrostatic two- stream instability to heat electrons along the background magnetic field directions. If the background magnetic field is not strong enough, the field-aligned heating can easily make the system unstable to the electromagnetic fire-hose instability. The nonlinear kinetic Alfven waves generated by the fire-hose instability can isotropize the electron pressure and heat ions by both ion-cyclotron instability and non-adiabatic ion gyro- reflections. Additional instabilities generated by the gyro-reflecting events can heat the plasma in a very efficient way. The importance of the cross-scale coupling between the ES instabilities and the EM instabilities in the space plasmas with counter-streaming plasma flows will be discussed.

  20. Artificial plasma cusp generated by upper hybrid instabilities in HF heating experiments at HAARP

    NASA Astrophysics Data System (ADS)

    Kuo, Spencer; Snyder, Arnold

    2013-05-01

    High Frequency Active Auroral Research Program digisonde was operated in a fast mode to record ionospheric modifications by the HF heating wave. With the O mode heater of 3.2 MHz turned on for 2 min, significant virtual height spread was observed in the heater off ionograms, acquired beginning the moment the heater turned off. Moreover, there is a noticeable bump in the virtual height spread of the ionogram trace that appears next to the plasma frequency (~ 2.88 MHz) of the upper hybrid resonance layer of the HF heating wave. The enhanced spread and the bump disappear in the subsequent heater off ionograms recorded 1 min later. The height distribution of the ionosphere in the spread situation indicates that both electron density and temperature increases exceed 10% over a large altitude region (> 30 km) from below to above the upper hybrid resonance layer. This "mini cusp" (bump) is similar to the cusp occurring in daytime ionograms at the F1-F2 layer transition, indicating that there is a small ledge in the density profile reminiscent of F1-F2 layer transitions. Two parametric processes exciting upper hybrid waves as the sidebands by the HF heating waves are studied. Field-aligned purely growing mode and lower hybrid wave are the respective decay modes. The excited upper hybrid and lower hybrid waves introduce the anomalous electron heating which results in the ionization enhancement and localized density ledge. The large-scale density irregularities formed in the heat flow, together with the density irregularities formed through the parametric instability, give rise to the enhanced virtual height spread. The results of upper hybrid instability analysis are also applied to explain the descending feature in the development of the artificial ionization layers observed in electron cyclotron harmonic resonance heating experiments.

  1. Numerical simulation of an atmospheric pressure RF-driven plasma needle and heat transfer to adjacent human skin using COMSOL.

    PubMed

    Schröder, Maximilian; Ochoa, Angel; Breitkopf, Cornelia

    2015-01-01

    Plasma medicine is an emerging field where plasma physics is used for therapeutical applications. Temperature is an important factor to take into account with respect to the applications of plasma to biological systems. During the treatment, the tissue temperature could increase to critical values. In this work, a model is presented, which is capable of predicting the skin temperature during a treatment with a radio frequency driven plasma needle. The main gas was helium. To achieve this, a discharge model was coupled to a heat transfer and fluid flow model. The results provide maximum application times for different power depositions in order to avoid reaching critical skin temperatures. PMID:25850416

  2. Evidence of weak plasma series resonance heating in the H-mode of neon and neon/argon inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Wendt, A. E.; Boffard, John B.; Jung, R. O.; Lin, Chun C.; Aneskavich, L. E.

    2012-10-01

    The shape of the electron energy distribution function (EEDF) in low-temperature plasmas governs the relative rates of electron-impact processes that determine key discharge properties. Comparison of EEDFs measured with probes and optical emission [1] in argon and neon inductively coupled plasmas (ICP) has revealed a surplus of high-energy electrons in neon-containing plasmas. The abundance of these extra high energy electrons is correlated with the sheath thickness near the rf antenna and can be reduced by either adding a Faraday shield or increasing the plasma density. These trends suggest an association of the surplus high-energy electrons with stochastic heating of electrons in capacitively-coupled electric fields in the sheath adjacent to the antenna. Conventional stochastic heating, however, is found to be insufficient to account for the EEDF observations, and a comparison of modeled and experimental values of the 13.56 MHz time modulation of select neon emission lines strongly suggests plasma series resonance (PSR) heating adjacent to the ICP antenna as the source of the extra high-energy electrons. [4pt] [1] Plasma Sources Sci. Technol. 20, (2011) 055006.

  3. Possibility of significant heating of H atoms in high-density, helicon-wave excited hydrogen plasmas

    NASA Astrophysics Data System (ADS)

    Sasaki, K.; Nakamoto, M.; Kadota, K.

    2001-10-01

    In the present work, we measured the distribution of H atom density in high-density hydrogen plasmas excited by helicon-wave discharges. The measurement was carried out in a linear machine with a uniform magnetic field of 1 kG along the cylindrical axis of the vacuum chamber. Plasmas were produced in a glass tube of 3 cm diameter by applying various rf powers to a helical antenna wound around the glass tube. The hydrogen gas pressure was 30--100 mTorr. Since the plasma was confined radially by the external magnetic field, we obtained a slender plasma column of 3 cm diameter at the center of the vacuum chamber. The distribution of the H atom density was measured by (2+1)-photon laser-induced fluorescence spectroscopy. As a result, it was found that the distribution of the H atom density had a deep dip in the high-density operation. The location of the dip corresponded to the high-density plasma column. A possible explanation for the deep dip in the plasma column is significant heating of H atoms. In general, it is known that temperatures of neutral species in low-pressure plasmas are not so far from room temperature. However, the present experimental result suggests the possibility of significant heating of neutral radicals in low-pressure, high-density plasmas. The high temperature may influence the transport and kinetics of reactive species in plasmas.

  4. Track method for the calculation of plasma heating by charged thermonuclear reaction products for axisymmetric flows

    NASA Astrophysics Data System (ADS)

    Frolova, A. A.; Khishchenko, K. V.; Charakhch'yan, A. A.

    2016-03-01

    Integral formulas for the three-dimensional case that give the plasma heating rate per unit volume are obtained using the track method and by integrating the well-known Cauchy problem for the steady-state homogeneous kinetic equation in the Fokker-Planck approximation in the absence of diffusion of the distribution function in the velocity space and under the condition that the velocity of the produced particles is independent on the direction of their escape. It is shown that both integral formulas are equivalent and, in the case of space homogeneous coefficients, turn into the model of local plasma heating away from the domain boundary. In addition to the known direct track method, the inverse method based on the approximation of the integral formula is developed. It is shown that the accuracy of the direct method is significantly decreased in the vicinity of the symmetry axis for not very fine angular grids. In the inverse method, the accuracy is not lost. It is shown that the computational cost of the inverse method can be significantly reduced without the considerable reduction of the computation accuracy.

  5. Filament Channels: Isolated Laboratories of Plasma Heating in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Panasenco, O.; Velli, M.

    2015-12-01

    Solar filament channels are complex systems comprising photospheric, chromospheric and coronal components. These components include magnetic neutral lines, supergranule cells, fibrils (spicules), filaments (prominences when observed on the limb), coronal cells, filament cavities and their overlying coronal arcades. Filaments are very highly structured and extend in height from the photosphere to the corona. Filament cores have chromospheric temperatures - 10,000 K (even at coronal heights ~ 100 Mm), surrounded by hotter plasma with temperature up to ~50,000 K. The whole filament is isolated from the rest of the solar corona by an envelope - the filament channel cavity - with temperatures of about 2,000,000 K. The filament channel cavity is even hotter than the solar corona outside the filament channel arcade. The compactness and big temperature variations make filament channels unique ready-to-go laboratories of coronal plasma heating and thermodynamics. In this work we discuss possible sources and mechanisms of heating in the filament channel environment. In particular, we address the mechanisms of magnetic canceling and current sheet dissipation.

  6. Impurity production and plasma performance in ASDEX discharges with ohmic and auxiliary heating

    NASA Astrophysics Data System (ADS)

    Fussmann, G.; ASDEX Team; NI Team; Icrh Team; Hofmann, J.; Janeschitz, G.; Lenoci, M.; Mast, F.; McCormick, K.; Murmann, H.; Poschenrieder, W.; Roth, J.; Setzensack, C.; Staudenmaier, G.; Steuer, K.-H.; Taglauer, E.; Verbeek, H.; Wagner, F.; Becker, G.; Bosch, H. S.; Brocken, H.; Eberhagen, A.; Gehre, O.; Gernhardt, J.; Gierke, G. V.; Clock, E.; Gruber, O.; Haas, G.; Izvozchikov, A.; Karger, F.; Kaufmann, M.; Keilhacker, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lisitano, G.; Mayer, H. M.; Meisel, D.; Mertens, V.; Müller, E. R.; Neuhauser, J.; Niedermeyer, H.; Noterdaeme, J.-M.; Pietrzyk, Z. A.; Rapp, H.; Riedler, H.; Röhr, H.; Ryter, F.; Schneider, F.; Siller, G.; Smeulders, P.; Söldner, F. X.; Speth, E.; Steinmetz, K.; Tsois, N.; Ugniewski, S.; Vollmer, O.; Wesner, F.; Zasche, D.

    1987-02-01

    A review is given on investigations in the ASDEX Tokamak on impurities in ohmically, NI and ICRH heated plasmas. For ohmic discharges in H 2 and D 2 it is found that iron release from the wall can be explained by sputtering due to neutral charge exchange (CX) atoms. In the case of He, however, significant contributions caused by ion sputtering are inferred. Comparing discharges with C limiters in He and D 2 suggests that in the case of hydrogen chemical processes are involved in C sputtering. By means of wall carbonization the concentrations of metal ions in the plasma could be substantially reduced. This achievement is of particular importance for NI counter-injection and ICRH, where under non-carbonized conditions severe impurity problems occur. We studied impurity confinement in the case of various heating scenarios by means of the laser injection technique. The poorest confinement is found for the L-phase of NI. Metal injection into the high confinement H-phase generally causes temporary suppression of the edge localized modes (ELM's). With respect to ICRH we conclude that enhanced wall erosion — probably due to the production of high energy ions in the boundary — together with a slightly increased impurity confinement is the dominant reason for the increase of the metallic concentrations. Impurity sputtering as an alternative strong erosion process was experimentally ruled out.

  7. Experiment and numerical simulation of RF heating in the Tandem Mirror plasma propulsion device

    NASA Technical Reports Server (NTRS)

    Yang, T. F.; Peng, S.; Chang-Diaz, F. R.

    1991-01-01

    Recent results of experimental and theoretical studies of ICRF heating of the plasma in the Tendem Mirror rocket are presented. The radial and axial profile of the magnetic field of the wave have been measured, and the data agree with the results from numerical simulation. One very important new finding is that the wave damped when it approached the resonance plane. This is a strong indication of beach heating effect and that RF power is absorbed by the ions in the plasma as expected. This power absorption phenomenon was also further confirmed by the refined analytical study of the wave propagation in a slab model. The electron density in the central cell has been measured by a microwave interferometer. The existence of two types of discharge similar to those of H-alpha emission have also been observed from the density measurements. A preliminary design of a flight system for a 100-day Mars transit has been undertaken. The specific weight for a 10 MW rocket is only 0.04 kg/kW.

  8. Divertor heat loads in RMP ELM controlled H-mode plasmas on DIII-D*

    SciTech Connect

    Jakubowski, M; Lasnier, C; Schmitz, O; Evans, T; Fenstermacher, M; Groth, M; Watkins, J; Eich, T; Moyer, R; Wolf, R; Baylor, L; Boedo, J; Burrell, K; Frerichs, H; deGrassie, J; Gohil, P; Joseph, I; Lehnen, M; Leonard, A; Petty, C; Pinsker, R; Reiter, D; Rhodes, T; Samm, U; Snyder, P; Stoschus, H; Osborne, T; Unterberg, B; West, W

    2008-10-13

    In this paper the manipulation of power deposition on divertor targets at DIII-D by application of resonant magnetic perturbations (RMPs) is analyzed. It has been found that heat transport shows a different reaction to the applied RMP depending on the plasma pedestal collisionality. At pedestal electron collisionality above 0.5 the heat flux during the ELM suppressed phase is of the same order as the inter-ELM in the non-RMP phase. Below this collisionality value we observe a slight increase of the total power flux to the divertor. This can be caused by much more negative potential at the divertor surface due to hot electrons reaching the divertor surface from the pedestal area and/or so called pump out effect. In the second part we discuss modification of ELM behavior due to the RMP. It is shown, that the width of the deposition pattern in ELMy H-mode depends linearly on the ELM deposited energy, whereas in the RMP phase of the discharge those patterns seem to be controlled by the externally induced magnetic perturbation. D{sub 2} pellets injected into the plasma bulk during ELM-free RMP H-mode lead in some cases to a short term small transients, which have very similar properties to ELMs in the initial RMP-on phase.

  9. Modeling of Plasma Conditions and Spectral Properties of Radiation-Heated Matter

    NASA Astrophysics Data System (ADS)

    Golovkin, Igor; Macfarlane, Joseph; Golovkina, Viktoriya; Nagayama, Taisuke; Bailey, James; Rochau, Gregory

    2015-11-01

    Opacity experiments at the Z facility provide important data for benchmarking opacity models and atomic data. The ability to accurately interpret the data obtained in these experiments increases the confidence in opacity calculations for a variety of astrophysical and laboratory problems. In the experiments, the Z dynamic hohlraum radiation source is used to both heat and backlight material samples. We will present the latest improvements to the simulation codes developed at Prism and how they affect the analysis of the experimental data. In particular, we will discuss angle-dependent radiation boundary condition recently implemented in the radiation-hydrodynamics code HELIOS. This improved modeling capability can potentially be important for studying behavior of plasmas driven by radiation sources that cannot be adequately described as neither directional nor Lambertian. We will also discuss atomic kinetics in radiatively heated samples and the possibility of its deviation from LTE. The effect of such deviation on both hydrodynamic evolution and radiative properties of these plasmas will be addressed.

  10. Mechanism of heating of pre-formed plasma electrons in relativistic laser-matter interaction

    SciTech Connect

    Paradkar, B. S.; Krasheninnikov, S. I.; Beg, F. N.

    2012-06-15

    The role of the longitudinal ambipolar electric field, present inside a pre-formed plasma, in electron heating and beam generation is investigated by analyzing single electron motion in the presence of one electromagnetic plane wave and 'V' shaped potential well (constant electric field) in a one dimensional slab approximation. It is shown that for the electron confined in an infinite potential well, its motion becomes stochastic when the ratio of normalized laser electric field a{sub 0}, to normalized longitudinal electric field E{sub z}, exceeds unity, i.e., a{sub 0}/E{sub z} Greater-Than-Or-Equivalent-To 1. For a more realistic potential well of finite depth, present inside the pre-formed plasma, the condition for stochastic heating of electrons gets modified to 1 Less-Than-Or-Equivalent-To a{sub 0}/E{sub z} Less-Than-Or-Equivalent-To {radical}(L), where L is the normalized length of the potential well. The energy of electron beam leaving such a potential well and entering the solid scales {approx}a{sub 0}{sup 2}/E{sub z}, which can exceed the laser ponderomotive energy ({approx}a{sub 0}) in the stochastic regime.

  11. Heating of ions by high frequency electromagnetic waves in magnetized plasmas

    SciTech Connect

    Zestanakis, P. A.; Kominis, Y.; Hizanidis, K.; Ram, A. K.

    2013-07-15

    The heating of ions by high frequency electrostatic waves in magnetically confined plasmas has been a paradigm for studying nonlinear wave-particle interactions. The frequency of the waves is assumed to be much higher than the ion cyclotron frequency and the waves are taken to propagate across the magnetic field. In fusion type plasmas, electrostatic waves, like the lower hybrid wave, cannot access the core of the plasma. That is a domain for high harmonic fast waves or electron cyclotron waves—these are primarily electromagnetic waves. Previous studies on heating of ions by two or more electrostatic waves are extended to two electromagnetic waves that propagate directly across the confining magnetic field. While the ratio of the frequency of each wave to the ion cyclotron frequency is large, the frequency difference is assumed to be near the ion cyclotron frequency. The nonlinear wave-particle interaction is studied analytically using a two time-scale canonical perturbation theory. The theory elucidates the effects of various parameters on the gain in energy by the ions—parameters such as the amplitudes and polarizations of the waves, the ratio of the wave frequencies to the cyclotron frequency, the difference in the frequency of the two waves, and the wave numbers associated with the waves. For example, the ratio of the phase velocity of the envelope formed by the two waves to the phase velocity of the carrier wave is important for energization of ions. For a positive ratio, the energy range is much larger than for a negative ratio. So waves like the lower hybrid waves will impart very little energy to ions. The theoretical results are found to be in good agreement with numerical simulations of the exact dynamical equations. The analytical results are used to construct mapping equations, simplifying the derivation of the motion of ions, which are, subsequently, used to follow the evolution of an ion distribution function. The heating of ions can then be

  12. Neutron emission from JET DT plasmas with RF heating on minority hydrogen

    NASA Astrophysics Data System (ADS)

    Henriksson, H.; Conroy, S.; Ericsson, G.; Gorini, G.; Hjalmarsson, A.; Källne, J.; Tardocchi, M.; EFDA-JET Workprogramme, contributors to the

    2002-07-01

    The neutron emission spectrum from d+t→α+n reactions has been measured as a means to study the plasma response to radio frequency (RF) power coupled to hydrogen and deuteron minority components (through fundamental and second harmonic, respectively) in a tritium discharge at JET. The spectrum was measured with the magnetic proton recoil spectrometer and was analysed in terms of two spectral components due to thermal (TH) and high-energy (HE) deuterons interacting with the bulk ion population of thermal tritons. The results were used to derive information on the deuteron population in terms of temperatures (TTH and THE) as well as corresponding particle and kinetic energy densities of the plasma; the bulk ion temperature (Ti = TTH) was determined both before (with Ohmic heating only) and during the RF pulse. Similar information on protons was derived from other measurements in order to estimate the different RF effects on protons and deuterons. This paper illustrates qualitatively the type of empirical ion kinetic information that can be obtained from neutron emission spectroscopy; the data serves as a basis for comparison with results of predictive and interpretative models on RF effects in plasmas.

  13. Plasma oxidative stress biomarkers, nitric oxide and heat shock protein 70 in trained elite soccer players.

    PubMed

    Banfi, G; Malavazos, A; Iorio, E; Dolci, A; Doneda, L; Verna, R; Corsi, M M

    2006-03-01

    The physiological response to the physical exercise involves a number of changes in the oxidative balance and in the metabolism of some important biological molecules, including nitric oxide (NO) and heat shock proteins (Hsp 70). With the aim to optimise previous laboratory diagnostic panels, we measured the plasma concentration of reactive oxygen metabolites (ROMs), total antioxidant status (TAS), glutathione reductase (GR) activity, and NO and Hsp 70 levels in 44 elite, antioxidant-supplemented and trained soccer players and in 15 sedentary controls. Although no statistically significant difference between athletes and controls was detected in the plasma level of ROMs and TAS, soccer players showed a significantly higher plasma GR activity, NO and Hst 70 levels than those of sedentary controls. These findings suggest that the measuring of relatively novel biomarkers in sport medicine, like GR, NO and Hsp 70, in addition to the well-known and reliable assays (d-ROMs test and TAS) may be useful to a clinician to better assess and evaluate the benefits of training and/or supplementation programs. PMID:16344941

  14. Enhancement of Localized ICRF Heating and Current Drive in TFTR D-T Plasmas

    SciTech Connect

    = G Schilling, First Author

    1997-04-15

    Theoretical advantages have led to an increased importance of the modification and sustainment of pressure and magnetic shear profiles in plasmas. We have demonstrated electron heating and current drive in TFTR (Tokamak Fusion Test Reactor) plasmas with the existing 43/63.6 MHz ICRF (ion cyclotron range of frequencies) system, both via the fast wave and via mode conversion of the fast wave to an ion-Bernstein wave. In order to achieve both on- and off-axis mode conversion in a pure D-T (deuterium-tritium) plasma, we have changed the operating frequency of two of our transmitters and antennas to 30 MHz and improved the launched directional wave spectrum. As a second step, two new four-strap fast-wave antennas have been installed, and a new four-strap direct-launch IBW antenna has been added as well. This reconfiguration and the resulting operating characteristics of the TFTR ICRF system in a variety of discharges will be presented.

  15. Effect of Ion Cyclotron Heating on Fast Ion Transport and Plasma Rotation in Tokamaks

    NASA Astrophysics Data System (ADS)

    Chan, V. S.; Omelchenko, Y. A.; Chiu, S. C.

    2000-10-01

    Minority ion cyclotron heating can produce energetic ions with banana orbits which are finite compared with the minor radius of a tokamak. The radial transport of the fast ions in the presence of Coulomb collisions results in a radial current and a corresponding JxB torque density on the bulk plasma. Collisions with the bulk ions provides an additional frictional torque that adds to or opposes the magnetic torque. This study clarifies the various mechanisms which can contribute to the torque components including collision-induced finite orbit particle diffusion, wave-induced asymmetry in canonical momentum when doppler resonance is accounted for, and orbit asymmetry created by magnetic geometry. Ion dynamics are calculated with a Monte-Carlo code in which wave-induced energy diffusion is accounted for by a quasilinear operator. The code follows particle drift trajectories in a tokamak geometry under the influence of RF fields and collisions with the background plasma. Questions on the direction of plasma rotation under different conditions and validity of the Green's function approach in modeling RF-induced rotation will be addressed.

  16. Particle Heating and Energization During Magnetic Reconnection Events in MST Plasmas

    NASA Astrophysics Data System (ADS)

    Dubois, Ami M.; Almagri, A. F.; Anderson, J. K.; den Hartog, D. J.; Forest, C.; Nornberg, M.; Sarff, J. S.

    2015-11-01

    Magnetic reconnection plays an important role in particle transport, energization, and acceleration in space, astrophysical, and laboratory plasmas. In MST reversed field pinch plasmas, discrete magnetic reconnection events release large amounts of energy from the equilibrium magnetic field, resulting in non-collisional ion heating. However, Thomson Scattering measures a decrease in the thermal electron temperature. Recent fast x-ray measurements show an enhancement in the high energy x-ray flux during reconnection, where the coupling between edge and core tearing modes is essential for enhanced flux. A non-Maxwellian energetic electron tail is generated during reconnection, where the power law spectral index (γ) decreases from 4.3 to 1.8 and is dependent on density, plasma current, and the reversal parameter. After the reconnection event, γ increases rapidly to 5.8, consistent with the loss of energetic electrons due to stochastic thermal transport. During the reconnection event, the change in γ is correlated with the change in magnetic energy stored in the equilibrium field, indicating that the released magnetic energy may be an energy source for electron energization. Recent experimental and computational results of energetic electron tail formation during magnetic reconnection events will be presented. This work is supported by the U.S. DOE and the NSF.

  17. Resonant Toroidal Alfven Eigenmodes (RTAEs) in Neutral Beam Heated Reverse Magnetic Shear Plasmas on TFTR

    SciTech Connect

    C.Z. Cheng; G.Y.-Fu; N.N. Gorelenkov; R. Nazikian; R.V. Budny

    1999-11-01

    Resonant Toroidal Alfven Eigenmodes (RTAEs) [1, 2] excited by neutral beam ions are observed in the region of the internal transport barrier in enhanced reverse shear (ERS) plasmas on TFTR. These modes occur in multiples of the same toroidal mode number in the range n=2-4 and appear as highly localized structures near the minimum in the q-profile with frequency near to that expected for TAEs. Unlike regular TAEs, these modes are observed in plasmas where the birth velocity of beam ions is well below the fundamental or sideband resonance condition. Theoretical analysis indicates that the Toroidicity induced Alfven Eigenmode (TAE) does not exist in these discharges due to strong pressure gradients (of the thermal and fast ions) which moves the mode frequency down into the lower Alfven continuum. However a new non-perturbative analysis (where the energetic particles are allowed to modify the mode frequency and mode structure) indicates that RTAEs can be driven by neutral beam ions in the weak magnetic shear region of ERS plasma, consistent with observations on TFTR. The importance of such modes is that they may affect the alpha particle heating profile or enhance the loss of energetic alpha particles in an advanced tokamak reactor where large internal pressure gradients and reverse magnetic shear operation are required to sustain large bootstrap current.

  18. Extended fusion yield integral using pathway idea in case of Shock-compressed heated plasma

    NASA Astrophysics Data System (ADS)

    Kumar, Dilip; Haubold, Hans

    The extended non-resonant thermonuclear reaction rate probability integral obtained in Haubold and Kumar [Haubold, H.J. and Kumar, D.: 2008, Extension of thermonuclear functions through the pathway model including Maxwell-Boltzmann and Tsallis distributions, Astroparticle Physics, 29, 70-76] is used to evaluate the fusion energy by itegrating it over temperature. The closed form representation of the extended reaction rate integral via Meijer's G-function is expressed as a solution of a homogeneous differential equation. A physical model of Guderley[Guderley G. :1942, Starke kugelige und zylindrische Verdichtungsstsse in der Nhe des Kugelmittelpunktes bzw. der Zylinderachse, Luftfahrtforschung, 19, 302] has been considered for the laser driven hydrodynamical process in a compressed fusion plasma and heated strong spherical shock wave. The fusion yield integral obtained in the paper is compared with the standard fusion yield ob-tained by Haubold and John [Haubold, H.J. and John, R.W.:1981, Analytical representation of the thermonuclear reaction rate and fusion energy production in a spherical plasma shock wave, Plasma Physics, 5, 399-411]. The pathway parameter used in this paper is given an interpretation in terms of moments.

  19. Observations of single-pass ion cyclotron heating in a trans-sonic flowing plasma

    NASA Astrophysics Data System (ADS)

    Bering, E. A.; Díaz, F. R. Chang; Squire, J. P.; Glover, T. W.; Carter, M. D.; McCaskill, G. E.; Longmier, B. W.; Brukardt, M. S.; Chancery, W. J.; Jacobson, V. T.

    2010-04-01

    The VAriable Specific Impulse Magnetoplasma Rocket (VASIMR®) is a high power electric spacecraft propulsion system, capable of Isp/thrust modulation at constant power [F. R. Chang Díaz et al., Proceedings of the 39th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, 8-11 Jan. 2001]. The VASIMR® uses a helicon discharge to generate plasma. This plasma is energized by an rf booster stage that uses left hand polarized slow mode waves launched from the high field side of the ion cyclotron resonance. In the experiments reported in this paper, the booster uses 2-4 MHz waves with up to 50 kW of power. This process is similar to the ion cyclotron heating (ICH) in tokamaks, but in the VASIMR® the ions only pass through the resonance region once. The rapid absorption of ion cyclotron waves has been predicted in recent theoretical studies. These theoretical predictions have been supported with several independent measurements in this paper. The single-pass ICH produced a substantial increase in ion velocity. Pitch angle distribution studies showed that this increase took place in the resonance region where the ion cyclotron frequency was roughly equal to the frequency on the injected rf waves. Downstream of the resonance region the perpendicular velocity boost should be converted to axial flow velocity through the conservation of the first adiabatic invariant as the magnetic field decreases in the exhaust region of the VASIMR®. This paper will review all of the single-pass ICH ion acceleration data obtained using deuterium in the first VASIMR® physics demonstrator machine, the VX-50. During these experiments, the available power to the helicon ionization stage increased from 3 to 20+ kW. The increased plasma density produced increased plasma loading of the ICH coupler. Starting with an initial demonstration of single-pass ion cyclotron acceleration, the experiments demonstrate significant improvements in coupler efficiency and in ion heating efficiency. In

  20. Evidence of plasma heating in solar microflares during the minimum of solar activity

    NASA Astrophysics Data System (ADS)

    Kirichenko, Alexey; Bogachev, Sergey

    We present a statistical study of 80 solar microflares observed during the deep minimum of solar activity between 23 and 24 solar cycles. Our analysis covers the following characteristics of the flares: thermal energy of flaring plasma, its temperature and its emission measure in soft X-rays. The data were obtained during the period from April to July of 2009, which was favorable for observations of weak events because of very low level of solar activity. The most important part of our analysis was an investigation of extremely weak microflares corresponding to X-ray class below A1.0. We found direct evidence of plasma heating in more than 90% of such events. Temperature of flaring plasma was determined under the isothermal approximation using the data of two solar instruments: imaging spectroheliometer MISH onboard Coronas-Photon spacecraft and X-ray spectrophotometer SphinX operating in energy range 0.8 - 15 keV. The main advantage of MISH is the ability to image high temperature plasma (T above 4 MK) without a low-temperature background. The SphinX data was selected due to its high sensitivity, which makes available the registration of X-ray emission from extremely weak microflares corresponding GOES A0.1 - A0.01 classes. The temperature we obtained lies in the range from 2.6 to 13.6 MK, emission measure, integrated over the range 1 - 8 Å - 2.7times10(43) - 4.9times10(47) cm (-3) , thermal energy of flaring region - 5times10(26) - 1.6times10(29) erg. We compared our results with the data obtained by Feldman et. al. 1996 and Ryan et. al. 2012 for solar flares with X-ray classes above A2.0 and conclude that the relation between X-ray class of solar flare and its temperature is strongly different for ordinary flares (above A2.0) and for weak microflares (A0.01 - A2.0). Our result supports the idea that weak solar events (microflares and nanoflares) may play significant a role in plasma heating in solar corona.