Note: This page contains sample records for the topic plasma microinstabilities from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Long-wavelength microinstabilities in toroidal plasmas  

SciTech Connect

Realistic kinetic toroidal eigenmode calculations have been carried out to support a proper assessment of the influence of long-wavelength microturbulence on transport in tokamak plasmas. In order to efficiently evaluate large-scale kinetic behavior extending over many rational surfaces, significant improvements have been made to a toroidal finite element code used to analyze the fully two-dimensional (r,[theta]) mode structures of trapped-ion and toroidal ion temperature gradient (ITG) instabilities. It is found that even at very long wavelengths, these eigenmodes exhibit a strong ballooning character with the associated radial structure relatively insensitive to ion Landau damping at the rational surfaces. In contrast to the long-accepted picture that the radial extent of trapped-ion instabilities is characterized by the ion-gyroradius-scale associated with strong localization between adjacent rational surfaces, present results demonstrate that under realistic conditions, the actual scale is governed by the large-scale variations in the equilibrium gradients. Applications to recent measurements of fluctuation properties in TFTR L-mode plasmas indicate that the theoretical trends appear consistent with spectral characteristics as well as rough heuristic estimates of the transport level. Benchmarking calculations in support of the development of a three-dimensional toroidal gyrokinetic code indicate reasonable agreement with respect to both the properties of the eigenfunctions and the magnitude of the eigenvalues during the linear phase of the simulations of toroidal ITG instabilities.

Tang, W.W.; Rewoldt, G.

1993-01-01

2

Long-wavelength microinstabilities in toroidal plasmas  

SciTech Connect

Realistic kinetic toroidal eigenmode calculations have been carried out to support a proper assessment of the influence of long-wavelength microturbulence on transport in tokamak plasmas. In order to efficiently evaluate large-scale kinetic behavior extending over many rational surfaces, significant improvements have been made to a toroidal finite element code used to analyze the fully two-dimensional (r,{theta}) mode structures of trapped-ion and toroidal ion temperature gradient (ITG) instabilities. It is found that even at very long wavelengths, these eigenmodes exhibit a strong ballooning character with the associated radial structure relatively insensitive to ion Landau damping at the rational surfaces. In contrast to the long-accepted picture that the radial extent of trapped-ion instabilities is characterized by the ion-gyroradius-scale associated with strong localization between adjacent rational surfaces, present results demonstrate that under realistic conditions, the actual scale is governed by the large-scale variations in the equilibrium gradients. Applications to recent measurements of fluctuation properties in TFTR L-mode plasmas indicate that the theoretical trends appear consistent with spectral characteristics as well as rough heuristic estimates of the transport level. Benchmarking calculations in support of the development of a three-dimensional toroidal gyrokinetic code indicate reasonable agreement with respect to both the properties of the eigenfunctions and the magnitude of the eigenvalues during the linear phase of the simulations of toroidal ITG instabilities.

Tang, W.W.; Rewoldt, G.

1993-01-01

3

Kinetic studies of microinstabilities in toroidal plasmas: Simulation and theory  

SciTech Connect

A comprehensive program for the development and use of particle simulation techniques for solving the gyrokinetic Vlasov-Maxwell equations on massively parallel computers has been carried out at Princeton Plasma Physics Laboratory. This is a key element of our ongoing theoretical efforts to systematically investigate physics issues vital to understanding tokamak plasmas. In this paper, our focus is on spatial-gradient-driven microinstabilities. Their importance is supported by the recent progress in achieving a physics-based understanding of anomalous transport in toroidal systems which has been based on the proposition that these drift-type electrostatic modes dependent on ion temperature gradient (ITG) and trapped particle effects are dominant in the bulk ( confinement'') region. Although their presence is consistent with a number of significant confinement trends, results from high temperature tokamaks such as TFTR have highlighted the need for better insight into the nonlinear properties of such instabilities in long-mean-free-path plasmas. In addressing this general issue, we report important new results including (i) the first fully toroidal 3D gyrokinetic simulation of ITG modes and (ii) realistic toroidal eigenmode calculations demonstrating the unique capability to deal with large scale kinetic behavior extending over many rational surfaces. The effects of ITG modes (iii) on the inward pinch of impurities in 3D slab geometry and (iv) on the existence of microtearing modes in 2D slab are also discussed. Finally, (v) sheared toroidal flow effects on trapped-particle modes are presented.

Lee, W.W.; Haham, T.S.; Parker, S.E.; Perkins, F.W.; Rath, S.; Rewoldt, G.; Reynders, J.V.W.; Santoro, R.A.; Tang, W.M.

1992-12-01

4

Kinetic studies of microinstabilities in toroidal plasmas: Simulation and theory  

SciTech Connect

A comprehensive program for the development and use of particle simulation techniques for solving the gyrokinetic Vlasov-Maxwell equations on massively parallel computers has been carried out at Princeton Plasma Physics Laboratory. This is a key element of our ongoing theoretical efforts to systematically investigate physics issues vital to understanding tokamak plasmas. In this paper, our focus is on spatial-gradient-driven microinstabilities. Their importance is supported by the recent progress in achieving a physics-based understanding of anomalous transport in toroidal systems which has been based on the proposition that these drift-type electrostatic modes dependent on ion temperature gradient (ITG) and trapped particle effects are dominant in the bulk (``confinement``) region. Although their presence is consistent with a number of significant confinement trends, results from high temperature tokamaks such as TFTR have highlighted the need for better insight into the nonlinear properties of such instabilities in long-mean-free-path plasmas. In addressing this general issue, we report important new results including (i) the first fully toroidal 3D gyrokinetic simulation of ITG modes and (ii) realistic toroidal eigenmode calculations demonstrating the unique capability to deal with large scale kinetic behavior extending over many rational surfaces. The effects of ITG modes (iii) on the inward pinch of impurities in 3D slab geometry and (iv) on the existence of microtearing modes in 2D slab are also discussed. Finally, (v) sheared toroidal flow effects on trapped-particle modes are presented.

Lee, W.W.; Haham, T.S.; Parker, S.E.; Perkins, F.W.; Rath, S.; Rewoldt, G.; Reynders, J.V.W.; Santoro, R.A.; Tang, W.M.

1992-12-01

5

Kinetic Self-Organization of Microinstabilities in Astrophysical and in Laboratory Plasmas  

NASA Astrophysics Data System (ADS)

Microinstabilities can be considered as effective collisions. The small scale electromagnetic fluctuations due to microinstabilties can be considered as collisions on the particles, leading to a similar point-like and instantaneous-like change in the particle momentum. This paradigm, the anomalous transport paradigm, requires us to derive theories that can predict the correct transport parameters (particularly the anomalous viscosity and anomalous resistivity) from the properties of the microinstabilties. Our recent work [1-3] has shown that another possible effect of microinstabilties is to lead to a direct macroscopic change in the equilibrium by affecting the plasma flow, temperature anisotropy and current profile on a macroscopic level. Our previous work has focused on space and astrophysical systems. But similar effects can be considered for experimental plasmas. A particularly intriguing possible analogy is with zonal flows and ``angular momentum generation'' believed to be happening in accretion disks in astrophysical systems [4] and with the ``spontaneous toroidal rotation'' of axisymmetric plasmas in fusion devices such as Jet and Alcator C-Mod [5]. [1] G. Lapenta, J.U. Brackbill, W.S. Daughton, Phys. Plasmas, 10, 1577 (2003). [2] W. Daughton, G. Lapenta, P. Ricci, Phys. Rev. Lett., 93, 105004, 2004 [3] P. Ricci, J.U. Brackbill, W.S. Daughton, G. Lapenta, Phys. Plasmas, 11, 4102, 2004. [4] B. Coppi 2002 Nucl. Fusion 42 1-4 [5] E. S. Marmar, et al., Fusion Energy 2002 (IAEA, Vienna) Paper OV/4-1

Lapenta, Giovanni

2006-04-01

6

Microinstability theory of the two-energy component fusion plasma system  

Microsoft Academic Search

The stability theory for the two-component system is developed from the Vlasov-Maxwell equations. Several modes of microinstability which are associated with neutral beam injection of alpha particle production in fusion reactions are studied using three different models for the fast ion distributions. First, the fast ion distribution function arising from neutral beam injection is found from solutions of the Fokker-Planck

L. P. Mai

1976-01-01

7

Unified fluid/kinetic description of plasma microinstabilities. Part I: Basic equations in a sheared slab geometry  

SciTech Connect

Unified fluid/kinetic equations for the plasma perturbed density ({ital {tilde n}}), parallel flow velocity ({ital {tilde u}}{sub {parallel}}) and temperature ({ital {tilde T}}) are developed in a sheared slab geometry by calculating the fluid moment closure relations kinetically. At first, a set of (unclosed) nonlinear perturbed fluid equations for {ital {tilde n}}, {ital {tilde u}}{sub {parallel}} and {ital {tilde T}} is developed using a drift ordering analysis and a new gyroviscous force ((spec. char. missing){center dot}{Pi}{sub {ital g}}). Thereafter, to develop linear closure relations for {bold b}{center dot}{del}{center dot}{tilde {Pi}}{sub {parallel}} and {ital {tilde q}}{sub {parallel}}, a drift-kinetic version of a new Chapman--Enskog-like (CEL) equation is developed and solved by using a moment approach and a physically realistic collision operator (Lorentz scattering operator plus the momentum restoring terms). The resultant closure relations for {bold b}{center dot}(spec. char. missing){center dot}{tilde {Pi}}{sub {parallel}} and {ital {tilde q}}{sub {parallel}} unify the fluid and kinetic approaches. In the collisional fluid limit the equations reduce to the well-known Braginskii equations. In the adiabatic limit they reproduce the usual kinetic results, including Landau damping. It is shown that this new CEL approach is more compatible with a fluidlike description of plasmas than the usual drift/gyrokinetic approach. Remarkably simplified forms of the closure relations are presented. The results are compared with other Landau damping models and shown to be more accurate, complete, and physically realistic. Applications of this set of equations to various microinstabilities in tokamak plasmas are presented in a separate paper (Part II) (Phys. Fluids B {bold 4}, 1182 (1992)).

Chang, Z.; Callen, J.D. (Department of Nuclear Engineering and Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706-1687 (United States))

1992-05-01

8

Toroidal microinstability studies of high temperature tokamaks  

SciTech Connect

Results from comprehensive kinetic microinstability calculations are presented showing the effects of toroidicity on the ion temperature gradient mode and its relationship to the trapped-electron mode in high-temperature tokamak plasmas. The corresponding particle and energy fluxes have also been computed. It is found that, although drift-type microinstabilities persist over a wide range of values of the ion temperature gradient parameter /eta//sub i/ /equivalent to/ (dlnT/sub i//dr)/(dlnn/sub i//dr), the characteristic features of the dominant mode are those of the /eta//sub i/-type instability when /eta//sub i/ > /eta//sub ic/ /approximately/1.2 to 1.4 and of the trapped-electron mode when /eta//sub i/ < /eta//sub ic/. 16 refs., 7 figs.

Rewoldt, G.; Tang, W.M.

1989-07-01

9

Microinstability Studies for the Large Helical Device  

SciTech Connect

Fully kinetic assessments of the stability properties of toroidal drift modes have been obtained for cases for the Large Helical Device (LHD). This calculation employs the comprehensive linear microinstability code FULL, as recently extended for nonaxisymmetric systems. The code retains the important effects in the linearized gyrokinetic equation, using the lowest-order ''ballooning representation'' for high toroidal mode number instabilities in the electrostatic limit. These effects include trapped particles, FLR, transit and bounce and magnetic drift frequency resonances, etc., for any number of plasma species. Results for toroidal drift waves destabilized by trapped electrons and ion temperature gradients are presented, using numerically-calculated three-dimensional MHD equilibria. These are reconstructed from experimental measurements. Quasilinear fluxes of particles and energy for each species are also calculated. Pairs of LHD discharges with different magnetic axis positions and with and without pellet injection are compared.

G. Rewoldt; L.-P. Ku; W.M. Tang; H. Sugama; N. Nakajima; K.Y. Watanabe; S. Murakami; H. Yamada; W.A. Cooper

2002-01-28

10

Gyrokinetic studies of microinstabilities in the reversed field pinch  

NASA Astrophysics Data System (ADS)

An analytic equilibrium, the Toroidal Bessel Function Model, is used in conjunction with the gyrokinetic code GYRO to investigate the nature of microinstabilities in a reversed field pinch plasma. The effect of the normalized electron plasma pressure ? on the characteristics of the microinstabilities is studied. At a ? of 4.5%, a transition between an ion temperature gradient (ITG) and a microtearing mode is observed. Suppression of the ITG mode occurs as in the tokamak, through coupling to shear Alfvén waves, with a critical ? for stability higher than its tokamak equivalent due to a shorter parallel connection length. A steep dependence of the microtearing growth rate on the temperature gradient suggests high profile stiffness. There is evidence for a collisionless microtearing mode. The properties of this mode are investigated, and it is found that electron curvature drift plays an important role in the instability.

Carmody, D.; Pueschel, M. J.; Terry, P. W.

2013-05-01

11

Change of confinement properties and transition from absolute to non-normal mode microinstabilities  

NASA Astrophysics Data System (ADS)

The change in confinement properties that can be induced in experiments, where the plasma is heated by an external injection system, is considered to be related to the transition from a regime where absolute microinstabilities are excited at the edge of the plasma column to a regime where these microinstabilities can exist only as nonnormal modes because of the effects of the local gradient of the E x B rotation frequency that is induced. Ion-temperature-gradient-driven modes are analyzed as an important example and the threshold conditions for their disappearances as normal modes are evaluated.

Basu, B.; Coppi, B.

1992-09-01

12

Gyrokinetic Simulations of Microinstabilities in Stellarator Geometry  

SciTech Connect

A computational study of microinstabilities in general geometry is presented. The ion gyrokinetic is solved as an initial value problem. The advantage of this approach is the accurate treatment of some important kinetic effects. The magnetohydrodynamic equilibrium is obtained from a three-dimensional local equilibrium model. The use of a local magnetohydrodynamic equilibrium model allows for a computationally-efficient systematic study of the impact of the magnetic structure on microinstabilities.

J.L.V. Lewandowski

2003-08-29

13

Microinstabilities in the high latitude F region: a brief review  

SciTech Connect

This is a review of the theory of plasma microinstabilities that may arise in the high latitude F region ionosphere below 1000 km. Three free energy sources are considered: a density gradient perpendicular to the ambient magnetic field B, a current parallel to B and a steady electric field perpendicular to B. The BGK model for charged-neutral collisions is used, and the short wavelength properties of the universal density drift, current convective and E x B gradient drift instabilities are compared. At sufficiently high altitudes and sufficiently steep gradients, the universal instability is the short wavelength mode most likely to grow and, through wave-particle diffusion, to cause relatively steep wavenumber dependences in power spectra.

Gary, S.P.

1983-01-01

14

Finite Beta Stabilization of Microinstabilities  

NASA Astrophysics Data System (ADS)

A new split-weight perturbative particle simulation scheme for finite-? plasmas is presented. The scheme is an improvement over the original split-weight scheme [W. W. Lee et. al, Phys. Plasmas 8, 4435 (2001)], which splits the perturbed particle response into adiabatic and non-adaibatic parts. In the new scheme, by further separating out the non-adaibatic response of the particles associated with the quasi-static bending of the magnetic field lines in the presence of background inhomogeneities of the plasma, we are able to demonstrate the finite-? stabilization of drift waves and ion temperature gradient modes using a simple gyrokinetic particle code based on realistic fusion plasma parameters. However, for ?mi/ me1, it becomes necessary to use the electron skin depth as the grid size of the simulation to achieve accuracy in solving the resulting singular perturbation equations, where the highest derivative term is multiplied by a smallness parameter. This conclusion is different from the prevailing wisdom that the numerical difficulty in simulation kinetic shear-Alfvén physics comes from the so-called Ampere cancellation. The proposed scheme is most suitable for studying finite-? physics in general geometry using straight field line coordinates. The work is supported by DoE Contract NO. DE-AC02-09CH11466.

Lee, W. W.; Startsev, E. A.

2010-11-01

15

Microinstability and internal impingement in overhead athletes.  

PubMed

A complex interplay exists between the static and dynamic stabilizers in the glenohumeral joint, especially in overheard athletes who need a shoulder hypermobile enough to perform overhead activity yet stable enough to prevent joint subluxation. Concomitant shoulder pathologies commonly occur in the setting of microinstability and internal impingement. Before any surgical intervention, a 3- to 6-month course of conservative measures should first be attempted, with exercises focused on rotator cuff and scapular stabilizer strengthening combined with posterior capsule stretching. If surgery is needed, arthroscopic suture plication with treatment of concomitant lesions has been shown to provide the best clinical outcomes. PMID:24079429

Chambers, Lauchlan; Altchek, David W

2013-08-20

16

Global-gyrokinetic study of finite ? effects on linear microinstabilities  

NASA Astrophysics Data System (ADS)

Electromagnetic microinstabilities in tokamak plasmas are studied by means of a linear global eigenvalue numerical code. Ion dynamics is described by the gyrokinetic equation, so that finite ion Larmor radius effects are taken into account to all orders. Nonadiabatic electrons are included in the model, with passing particles described by the drift-kinetic equation and trapped particles through the bounce averaged drift-kinetic equation. A large aspect ratio plasma with circular shifted surfaces is considered for the numerical implementation. The effects of an electromagnetic perturbation on toroidal ion temperature gradient driven modes are studied, confirming the stabilization of these modes with increasing ? (parameter identifying the ratio of the plasma pressure to the magnetic pressure). The threshold for the destabilization of an electromagnetic mode, the so-called kinetic ballooning mode or Alfvénic ion temperature gradient mode is identified. Moreover, owing to the global formulation, the radial structure of these electromagnetic modes is observed for the first time. Finally, the contributions of trapped electron dynamics and the effects of the Shafranov shift are addressed.

Falchetto, G. L.; Vaclavik, J.; Villard, L.

2003-05-01

17

Survey of microinstability and simulated turbulent transport in NSTX  

NASA Astrophysics Data System (ADS)

Linear gyrokinetic simulations demonstrate a large variety of microinstabilities are possible in NSTX. Microtearing modes are often unstable in the core region (r/a=0.5-0.8) of NBI heated H-modes. In cases without Lithium wall conditioning, the local ExB shearing rates are larger than linear growth rates (r/a=0.5-0.6). Instead, the ETG instability (at electron scales) is unstable; nonlinear simulations in this region will be presented. Farther out (r/a=0.7-0.8), and in plasmas with Lithium wall conditioning, other ion scale instabilities can co-exist with, or dominate, microtearing modes. The nature of these ballooning modes is complicated and can exhibit ITG/TEM or KBM behavior depending on the MHD alpha parameter (?MHD=-q^2R??). In limited cases tearing-parity ITG modes have also been identified. While non-linear simulations of these ``mixed-mode'' conditions are challenging, first attempts are underway. This work is supported by US DOE contract DE-AC02-09CH11466.

Guttenfelder, Walter; Candy, Jeff; Kaye, Stanley; Bell, Ronald; Leblanc, Benoit; Ren, Yang; Yuh, Howard

2012-10-01

18

Emerging topics on the hip: ligamentum teres and hip microinstability.  

PubMed

Microinstability and ligament teres lesions are emergent topics on the hip pathology. These entities are an increasingly recognized cause of persistent hip pain and should be considered in the differential diagnosis of the patient with hip pain. Conventional (non-arthrographic) CT and MR have a very limited role in the evaluation of these entities. CTa and MRa have emerged as the modalities of choice for pre-operative imaging of ligamentum teres injuries and microinstability. To date, pre-operative imaging detection of these pathologies is not widespread but with appropriate imaging and a high index of suspicion, preoperative detection should improve. This article discusses current concepts regarding anatomy, biomechanics, clinical findings, diagnosis and treatment of ligament teres lesions and microinstability. PMID:21723682

Cerezal, Luis; Arnaiz, Javier; Canga, Ana; Piedra, Tatiana; Altónaga, José R; Munafo, Ricardo; Pérez-Carro, Luis

2011-07-01

19

Comparison of Microinstability Properties for Stellarator Magnetic Geometries  

SciTech Connect

The microinstability properties of seven distinct magnetic geometries corresponding to different operating and planned stellarators with differing symmetry properties are compared. Specifically, the kinetic stability properties (linear growth rates and real frequencies) of toroidal microinstabilities (driven by ion temperature gradients and trapped-electron dynamics) are compared, as parameters are varied. The familiar ballooning representation is used to enable efficient treatment of the spatial variations along the equilibrium magnetic field lines. These studies provide useful insights for understanding the differences in the relative strengths of the instabilities caused by the differing localizations of good and bad magnetic curvature and of the presence of trapped particles. The associated differences in growth rates due to magnetic geometry are large for small values of the temperature gradient parameter n identical to d ln T/d ln n, whereas for large values of n, the mode is strongly unstable for all of the different magnetic geometries.

G. Rewoldt; L.-P. Ku; W.M. Tang

2005-06-16

20

Characteristics of microinstabilities in electron cyclotron and ohmic heated discharges  

SciTech Connect

Characteristics of microinstabilities in electron cyclotron (EC) and ohmic heated (OH) discharges in the T10 tokamak have been analyzed by linear electrostatic gyrokinetic simulations with gyro[J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] aiming to find insights into the effect of auxiliary heating on the transport. Trapped electron modes are found to be unstable in both OH and the EC heated scenarios. In the OH case the main drive is from the density gradient and in the EC case from the electron temperature gradient. The growth rates and particle fluxes exhibit qualitatively different scaling with the electron-to-ion temperature ratios in the two cases. This is mainly due to the fact that the dominant drives and the collisionalities are different. The inward flow velocity of impurities and the impurity diffusion coefficient decreases when applying EC heating, which leads to lower impurity peaking, consistently with experimental observations.

Pusztai, I.; Moradi, S.; Fueloep, T. [Department of Applied Physics, Nuclear Engineering, Chalmers University of Technology and Euratom-VR Association, Goeteborg (Sweden); Timchenko, N. [Institute of Tokamak Physics, NRC ''Kurchatov Institute,'' 123182, Kurchatov Sq. 1, Moscow (Russian Federation)

2011-08-15

21

MICROINSTABILITY OF THE SHOULDER IN THE OVERHEAD ATHLETE  

PubMed Central

The overhead throwing athlete is an extremely challenging patient in sports medicine. The repetitive microtraumatic stresses and extreme ranges of motion observed within the athlete’s shoulder joint complex during the throwing motion constantly place the athlete at risk for injury. While gross instability of the shoulder is possible, microinstability is seen far more frequently and is associated with a variety of different pathologies, including rotator cuff tendonitis, internal impingement, and labral lesions. Treatment of the overhead athlete requires the understanding of several principles based on the unique physical characteristics of this type of athlete and the demands placed upon the static stabilizing structures during the act of throwing. The purpose of this paper is to describe these principles and incorporate them into in a multi?phase progressive rehabilitation program designed to prevent injuries and rehabilitate the injured athlete, both non?operatively and postoperatively.

Curtis, Alan S.

2013-01-01

22

The Effect of Trapped Ions and Current Drive on Tokamak Microinstabilities: Theory and Simulations  

Microsoft Academic Search

In this work, a range of low-frequency microinstabilities in tokamaks and the related anomalous cross field transports have been investigated analytically and numerically. A unified theory of temperature gradient driven trapped ion modes and ballooning instabilities is developed using kinetic theory in banana regimes. All known results, such as electrostatic and purely magnetic trapped particle modes and ideal MHD ballooning

Xue Qiao Xu

1990-01-01

23

Unified fluid/kinetic description of magnetized plasmas. Part 2, Applications.  

National Technical Information Service (NTIS)

The unified fluid/kinetic equations developed in part 1 of this work are used to study plasma drift type microinstabilities. A generalized perturbed Ohm's law derived which is uniformly valid for arbitrary collisionality (omega)/(nu) and adiabaticity (ome...

Z. Chang J. D. Callen

1991-01-01

24

Microinstability-based models for confinement properties and ignition criteria in tokamaks  

SciTech Connect

This paper reports on results of theoretical studies dealing with: (1) the use of microinstability-based thermal transport models to interpret the anomalous confinement properties observed in key tokamak experiments such as TFTR and (2) the likely consequences of the presence of such instabilities for future ignition devices. Transport code simulations using profile-consistent forms of anomalous thermal diffusivities due to drift-type instabilities have yielded good agreement with the confinement times and temperatures observed in TFTR under a large variety of operating conditions including pellet-fuelling in both ohmic- and neutral-beam-heated discharges. With regard to achieving an optimal ignition margin, the adverse temperature scaling of anomalous losses caused by drift modes leads to the conclusion that it is best to operate at the maximum allowable density while holding the temperature close to the minimum value required for ignition.

Tang, W.M.; Bishop, C.M.; Coppi, B.; Kaye, S.M.; Perkins, F.W.; Redi, M.H.; Rewoldt, G.

1987-02-01

25

A comprehensive gyrokinetic description of global electrostatic microinstabilities in a tokamak  

SciTech Connect

It is believed that low frequency microinstabilities such as ion temperature gradient (ITG) driven modes and trapped electron modes (TEMs) are largely responsible for the experimentally observed anomalous transport via the ion and electron channels in a tokamak. In the present work, a comprehensive global linear gyrokinetic model incorporating fully kinetic (trapped and passing) electrons and ions, actual ion to electron mass ratio, radial coupling, and profile variation is used to investigate the ITG driven modes and pure TEMs. These modes are found to exhibit multiscale structures in the presence of nonadiabatic passing electrons. The multiscale structure is related to the large nonadiabaticity of electrons in the vicinity of mode rational magnetic surfaces and leads to reduced mixing length estimates of transport compared to those obtained from adiabatic electron models.

Chowdhury, J.; Ganesh, R. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India); Brunner, S.; Vaclavik, J.; Villard, L. [CRPP, Association EURATOM-Confederation Suisse, EPFL, 1015 Lausanne (Switzerland); Angelino, P. [Association Euratom-CEA, CEA/DSM/DRFC, Cadarache, 13108 St. Paul-lez-Durance (France)

2009-05-15

26

A model for microinstability destabilization and enhanced transport in the presence of shielded 3D magnetic perturbations  

NASA Astrophysics Data System (ADS)

A mechanism is presented that suggests shielded 3D magnetic perturbations can destabilize microinstabilities and enhance the associated anomalous transport. Using local 3D equilibrium theory, shaped tokamak equilibria with small 3D deformations are constructed. In the vicinity of rational magnetic surfaces, the infinite-n ideal MHD ballooning stability boundary is strongly perturbed by the 3D modulations of the local magnetic shear associated with the presence of near-resonant Pfirsch-Schlüter currents. These currents are driven by 3D components of the magnetic field spectrum even when there is no resonant radial component. The infinite-n ideal ballooning stability boundary is often used as a proxy for the onset of virulent kinetic ballooning modes and associated stiff transport. These results suggest that the achievable pressure gradient may be lowered in the vicinity of low order rational surfaces when 3D magnetic perturbations are applied. This mechanism may provide an explanation for the observed reduction in the peak pressure gradient at the top of the edge pedestal during experiments where edge localized modes have been completely suppressed by applied 3D magnetic fields.

Bird, T. M.; Hegna, C. C.

2013-01-01

27

Gyrokinetic Calculations of Microinstabilities and Transport During RF H-Modes on Alcator C-Mod  

SciTech Connect

Physics understanding for the experimental improvement of particle and energy confinement is being advanced through massively parallel calculations of microturbulence for simulated plasma conditions. The ultimate goal, an experimentally validated, global, non-local, fully nonlinear calculation of plasma microturbulence is still not within reach, but extraordinary progress has been achieved in understanding microturbulence, driving forces and the plasma response in recent years. In this paper we discuss gyrokinetic simulations of plasma turbulence being carried out to examine a reproducible, H-mode, RF heated experiment on the Alcator CMOD tokamak3, which exhibits an internal transport barrier (ITB). This off axis RF case represents the early phase of a very interesting dual frequency RF experiment, which shows density control with central RF heating later in the discharge. The ITB exhibits steep, spontaneous density peaking: a reduction in particle transport occurring without a central particle source. Since the central temperature is maintained while the central density is increasing, this also suggests a thermal transport barrier exists. TRANSP analysis shows that ceff drops inside the ITB. Sawtooth heat pulse analysis also shows a localized thermal transport barrier. For this ICRF EDA H-mode, the minority resonance is at r/a * 0.5 on the high field side. There is a normal shear profile, with q monotonic.

M.H. Redi; C. Fiore; P. Bonoli; C. Bourdelle; R. Budny; W.D. Dorland; D. Ernst; G. Hammett; D. Mikkelsen; J. Rice; S. Wukitch

2002-06-18

28

Comparing Linear Microinstability of the National Compact Stellarator Expriment and a Shaped Tokamak  

SciTech Connect

One metric for comparing con nement properties of di erent magnetic fusion energy con gurations is the linear critical gradient of drift wave modes. The critical gradient scale length determines the ratio of the core to pedestal temperature when a plasma is limited to marginal stability in the plasma core. The gyrokinetic turbulence code GS2 was used to calculate critical temperature gradients for the linear, collisionless ion tem- perature gradient (ITG) mode in the National Compact Stellarator Experiment (NCSX) and a prototypical shaped tokamak, based on the pro les of a JET H-mode shot and the stronger shaping of ARIES-AT. While a concern was that the narrow cross section of NCSX at some toroidal locations would result in steep gradients that drive instabilities more easily, it is found that other stabilizing e ects of the stellarator con guration o set this so that the normalized critical gradients for NCSX are competitive with or even better than for the tokamak. For the adiabatic ITG mode, NCSX and the tokamak had similar critical gradients, though beyond marginal stability, NCSX had larger growth rates. However, for the kinetic ITG mode, NCSX had a higher critical gradient and lower growth rates until a/LT ?#25; 1:5 a/LT;crit, when it surpassed the tokamak's. A discussion of the results presented with respect to a/LT vs R/LT is included.

J.A. Baumgaertel, G.W. Hammett and D.R. Mikkelsen

2012-11-20

29

Stellarator and tokamak plasmas: a comparison  

NASA Astrophysics Data System (ADS)

An overview is given of physics differences between stellarators and tokamaks, including magnetohydrodynamic equilibrium, stability, fast-ion physics, plasma rotation, neoclassical and turbulent transport and edge physics. Regarding microinstabilities, it is shown that the ordinary, collisionless trapped-electron mode is stable in large parts of parameter space in stellarators that have been designed so that the parallel adiabatic invariant decreases with radius. Also, the first global, electromagnetic, gyrokinetic stability calculations performed for Wendelstein 7-X suggest that kinetic ballooning modes are more stable than in a typical tokamak.

Helander, P.; Beidler, C. D.; Bird, T. M.; Drevlak, M.; Feng, Y.; Hatzky, R.; Jenko, F.; Kleiber, R.; Proll, J. H. E.; Turkin, Yu; Xanthopoulos, P.

2012-12-01

30

Numerical analysis of the impact of the ion threshold, ion stiffness and temperature pedestal on global confinement and fusion performance in JET and in ITER plasmas  

Microsoft Academic Search

Understanding the impact of micro-instabilities on the global plasma performance is essential in order to make realistic predictions for relevant tokamak scenarios. The semi-empirical transport model CGM is a useful tool to this scope because it depends explicitly on the threshold and the stiffness level, two key parameters of turbulent transport as driven by the ITG\\/TEM instabilities. The CGM then

B Baiocchi; P Mantica; T Tala; G Corrigan; E Joffrin; K Kirov; V Naulin

2012-01-01

31

ACTIVE MEDIA: Influence of vibrational kinetics of HCl on the growth of microinstabilities and the characteristics of an electric-discharge XeCl laser under inhomogeneous preionisation conditions  

Microsoft Academic Search

A one-dimensional model of an electric-discharge XeCl laser was used in an investigation of the growth of microinstabilities induced by perturbations both of the initial electron density and of the electric field under homogeneous field and inhomogeneous preionisation conditions. A mechanism of attachment---vibrational stabilisation of a discharge in mixtures containing HCl molecules was proposed and investigated. It was found that

A. V. Dem'yanov; Igor'V. Kochetov; A. P. Napartovich; M. Capitelli; S. Longo

1995-01-01

32

Effect of alpha drift and instabilities on tokamak plasma edge conditions  

SciTech Connect

As suprathermal fusion products slow down in a Tokamak, their average drift is inward. The effect of this drift on the alpha heating and thermalization profiles is examined. In smaller TFTR-type devices, heating in the outer region can be cut in half. Also, the fusion-product energy-distribution near the plasma edge has a positive slope with increasing energy, representing a possible driving mechanism for micro-instabilities. Another instability that can seriously affect outer plasma conditions and shear Alfven transport of alphas is also considered.

Miley, G H; Choi, C K

1983-01-01

33

Plasma rotation and transport in MAST spherical tokamak  

NASA Astrophysics Data System (ADS)

The formation of internal transport barriers (ITBs) is investigated in MAST spherical tokamak plasmas. The relative importance of equilibrium flow shear and magnetic shear in their formation and evolution is investigated using data from high-resolution kinetic- and q-profile diagnostics. In L-mode plasmas, with co-current directed NBI heating, ITBs in the momentum and ion thermal channels form in the negative shear region just inside qmin. In the ITB region the anomalous ion thermal transport is suppressed, with ion thermal transport close to the neo-classical level, although the electron transport remains anomalous. Linear stability analysis with the gyro-kinetic code GS2 shows that all electrostatic micro-instabilities are stable in the negative magnetic shear region in the core, both with and without flow shear. Outside the ITB, in the region of positive magnetic shear and relatively weak flow shear, electrostatic micro-instabilities become unstable over a wide range of wave numbers. Flow shear reduces the linear growth rates of low-k modes but suppression of ITG modes is incomplete, which is consistent with the observed anomalous ion transport in this region; however, flow shear has little impact on growth rates of high-k, electron-scale modes. With counter-NBI ITBs of greater radial extent form outside qmin due to the broader profile of E × B flow shear produced by the greater prompt fast-ion loss torque.

Field, A. R.; Michael, C.; Akers, R. J.; Candy, J.; Colyer, G.; Guttenfelder, W.; Ghim, Y.-c.; Roach, C. M.; Saarelma, S.; MAST Team

2011-06-01

34

Plasma confinement experiments in the TMX tandem mirror. Paper IAEA-CN-38/F-1  

SciTech Connect

Results from the new Tandem Mirror Experiment (TMX) are described. Tandem-mirror density and potential profiles are produced using end-plug neutral-beam injection and central-cell gas-fueling. TMX parameters are near those predicted theoretically. The end-plug electron temperature is higher than in the comparably sized single-mirror 2XIIB. Axial confinement of the finite-beta central-cell plasma is improved by the end plugs by as much as a factor of 9. In TMX, end-plug microinstability limits central-cell confinement in agreement with theory.

Simonen, T.C.; Anderson, C.A.; Casper, T.A.

1980-05-22

35

Nonlinear electromagnetic gyrokinetic equations for rotating axisymmetric plasmas  

SciTech Connect

The influence of sheared equilibrium flows on the confinement properties of tokamak plasmas is a topic of much current interest. A proper theoretical foundation for the systematic kinetic analysis of this important problem has been provided here by presented the derivation of a set of nonlinear electromagnetic gyrokinetic equations applicable to low frequency microinstabilities in a rotating axisymmetric plasma. The subsonic rotation velocity considered is in the direction of symmetry with the angular rotation frequency being a function of the equilibrium magnetic flux surface. In accordance with experimental observations, the rotation profile is chosen to scale with the ion temperature. The results obtained represent the shear flow generalization of the earlier analysis by Frieman and Chen where such flows were not taken into account. In order to make it readily applicable to gyrokinetic particle simulations, this set of equations is cast in a phase-space-conserving continuity equation form.

Artun, M.; Tang, W.M.

1994-03-01

36

Effects of fueling profiles on plasma transport  

SciTech Connect

A one-dimensional (1-D), multifluid transport model is used to investigate the effects of particle fueling profiles on plasma transport in an ignition-sized tokamak (TNS). Normal diffusive properties of plasmas will likely maintain the density at the center of the discharge even if no active fueling is provided there. This significantly relaxes the requirements for fuel penetration. Not only is lower fuel penetration easier to achieve, but it may have the advantage of reducing or eliminating density gradient-driven trapped particle microinstabilities. Simulation of discrete pellet fueling indicates that relatively low velocity (approximately 10/sup 3/ m/sec) pellets may be sufficient to fuel a TNS-sized device (approximately 1.25-m minor radius), to produce a relatively broad, cool edge region of plasma which should reduce the potential for sputtering, and also to reduce the likelihood of trapped particle mode dominated transport. Low penetrating pellets containing up to 10 to 20 percent of the total plasma ions can produce fluctuations in density and temperature at the plasma edge, but the pressure profile and fusion alpha production remain almost constant.

Mense, A. T.; Houlberg, W. A.; Attenberger, S. E.; Milora, S. L.

1978-04-01

37

Gyrokinetic Simulation of Finite-Beta Plasmas on Parallel Architectures  

NASA Astrophysics Data System (ADS)

There exists a wide body of research on the linear and non-linear properties of plasma microinstabilities which are induced by density and temperature gradients. Recently, however, there has been an interest in the electromagnetic or "finite-beta" effects on these microinstabilities. This thesis focuses on the finite -beta modification of an ion temperature gradient (ITG) driven microinstability in a two-dimensional shearless and sheared-slab geometries. A gyrokinetic model is employed in both the numerical and analytic studies of this instability. This thesis is outlined as follows: Chapter 1 introduces the electromagnetic gyrokinetic model which is employed in both the numerical and analytic studies of the ITG instability. Some discussion of the Klimontovich particle representation of the gyrokinetic Vlasov equation and a multiple scale model of the background plasma gradient is also presented. Chapter 2 describes in more detail the computational issues facing an electromagnetic gyrokinetic particle simulation of the ITG mode. An electromagnetic extension of the partially linearized algorithm is presented along with a comparison of quiet particle initialization routines. Chapter 3 presents and compares algorithms for the gyrokinetic particle simulation technique on SIMD and MIMD computing platforms. Chapter 4 discusses electromagnetic gyrokinetic fluctuation theory and provides a comparison of analytic and numerical results. An anomalous numerical instability is reported which does not correspond to the normal modes of the system. Some suggestions as to this instability's origin are presented. Chapter 5 contains both a linear and a non-linear three-wave coupling analysis of the finite-beta modified ITG mode in a shearless slab geometry. Comparisons are made with linear and partially linearized gyrokinetic simulation results. Finally, Chapter 6 presents results from a finite -beta modified ITG mode in a sheared slab geometry. The linear dispersion relation is derived and results from an integral eigenvalue code are presented. Comparisons are made with the gyrokinetic particle code in a variety of limits with both adiabatic and non-adiabatic electrons. Evidence of ITG driven microtearing is presented.

Reynders, John Van Wicheren

1993-01-01

38

Kinetic instabilities that limit ? in the edge of a tokamak plasma: a picture of an H-mode pedestal.  

PubMed

Plasma equilibria reconstructed from the Mega-Amp Spherical Tokamak have sufficient resolution to capture plasma evolution during the short period between edge-localized modes (ELMs). Immediately after the ELM, steep gradients in pressure, P, and density, n(e), form pedestals close to the separatrix, and they then expand into the core. Local gyrokinetic analysis over the ELM cycle reveals the dominant microinstabilities at perpendicular wavelengths of the order of the ion Larmor radius. These are kinetic ballooning modes in the pedestal and microtearing modes in the core close to the pedestal top. The evolving growth rate spectra, supported by gyrokinetic analysis using artificial local equilibrium scans, suggest a new physical picture for the formation and arrest of this pedestal. PMID:22540707

Dickinson, D; Roach, C M; Saarelma, S; Scannell, R; Kirk, A; Wilson, H R

2012-03-26

39

Kinetic Instabilities that Limit ? in the Edge of a Tokamak Plasma: A Picture of an H-Mode Pedestal  

NASA Astrophysics Data System (ADS)

Plasma equilibria reconstructed from the Mega-Amp Spherical Tokamak have sufficient resolution to capture plasma evolution during the short period between edge-localized modes (ELMs). Immediately after the ELM, steep gradients in pressure, P, and density, ne, form pedestals close to the separatrix, and they then expand into the core. Local gyrokinetic analysis over the ELM cycle reveals the dominant microinstabilities at perpendicular wavelengths of the order of the ion Larmor radius. These are kinetic ballooning modes in the pedestal and microtearing modes in the core close to the pedestal top. The evolving growth rate spectra, supported by gyrokinetic analysis using artificial local equilibrium scans, suggest a new physical picture for the formation and arrest of this pedestal.

Dickinson, D.; Roach, C. M.; Saarelma, S.; Scannell, R.; Kirk, A.; Wilson, H. R.

2012-03-01

40

CONFERENCE DESCRIPTION Theory of Fusion Plasmas: Varenna-Lausanne International Workshop  

NASA Astrophysics Data System (ADS)

The Joint Varenna-Lausanne international workshop on Theory of Fusion Plasmas takes place every other year in a place particularly favourable for informal and in-depth discussions. Invited and contributed papers present state-of-the-art research in theoretical plasma physics, covering all domains relevant to fusion plasmas. This workshop always welcomes a fruitful mix of experienced researchers and students, to allow a better understanding of the key theoretical physics models and applications. Theoretical issues related to burning plasmas Anomalous Transport (Turbulence, Coherent Structures, Microinstabilities) RF Heating and Current Drive Macroinstabilities Plasma-Edge Physics and Divertors Fast particles instabilities Further details: http://Varenna-Lausanne.epfl.ch The conference is organized by: Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, Association EURATOM - Confédération Suisse 'Piero Caldirola' International Centre for the Promotion of Science and International School of Plasma Physics Istituto di Fisica del Plasma del CNR, Milano Editors: X Garbet (CEA, Cadarache, France) and O Sauter (CRPP-EPFL, Lausanne, Switzerland)

Garbet, X.; Sauter, O.

2010-12-01

41

The modified plasma dispersion function  

SciTech Connect

In the linear theory of waves in a hot plasma if the zeroth-order velocity distribution function is taken to be Maxwellian, then there arises a special, complex-valued function of a complex variable {xi}={ital x}+{ital iy}, namely {bold Z}({xi}), known as the plasma dispersion function. In space physics many particle distributions possess a high-energy tail that can be well modeled by a generalized Lorentzian (or kappa) distribution function containing the spectral index {kappa}. In this paper, as a natural analog to the definition of {bold Z}({xi}), a new special function {bold Z}{sup *}{sub {kappa}}({xi}) is defined based on the kappa distribution function. Here, {bold Z}{sup *}{sub {kappa}}({xi}) is called the modified plasma dispersion function. For any positive integral value of {kappa}, {bold Z}{sup *}{sub {kappa}}({xi}) is calculated in closed form as a finite series. General properties, including small-argument and large-argument expansions, of {bold Z}{sup *}{sub {kappa}}({xi}) are given, and simple explicit forms are given for {bold Z}{sup *}{sub 1}({xi}), {bold Z}{sup *}{sub 2}({xi}), ..., {bold Z}{sup *}{sub 6}({xi}). A comprehensive set of graphs of the real and imaginary parts of {bold Z}{sup *}{sub {kappa}}({xi}) is presented. It is demonstrated how the modified plasma dispersion function approaches the plasma dispersion function in the limit as {kappa}{r arrow}{infinity}, a result to be expected since the (appropriately defined) kappa distribution function formally approaches the Maxwellian as {kappa}{r arrow}{infinity}. The function {bold Z}{sup *}{sub {kappa}}({xi}) is expected to be instrumental in studying microinstabilities in plasmas when the particle distribution function is not only the standard generalized Lorentzian, but also of the Lorentzian type,including {ital inter} {ital alia}, the loss-cone, bi-Lorentzian, and product bi-Lorentzian distributions.

Summers, D. (Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland A1C5S7, Canada (CA)); Thorne, R.M. (Department of Atmospheric Sciences, University of California at Los Angeles, Los Angeles, California 90024-1565 (USA))

1991-08-01

42

Runaway electrons and turbulence in a current-carrying stellarator plasma  

SciTech Connect

A disruption of the free acceleration of electrons in a magnetized, ohmically heated plasma in the Uragan-2 and Sirius stellarators has been observed and studied. Depending on the electric field and the ratio E/E/sub c//sub r/, the plasma heating in a stellarator may fall in one of three regimes associated with the appearance of a tail on the electron energy distribution: free acceleration (runaway) of electrons in a relatively cool plasma with a classical conductivity, at E<0.1E/sub c//sub r/; limited acceleration at Eapprox.(0.1--1.0)E/sub c//sub r/; and total disruption of the free acceleration in a hot plasma at E>E/sub c//sub r/. The behavior of the electron tail from one regime to another over the course of the discharge is related to the development of various stages of microinstabilities near the plasma frequency ..omega../sub pe/ and the ion plasma frequency ..omega../sub ..pi../. It appears that these instabilities stabilize the current drift velocity at various levels. The turbulent heating of electrons and ions at the anomalous resistance and the suppression of the free electron acceleration arise near a threshold Eapprox.E/sub c//sub r/. Results on the turbulent heating of ions carried out in various tokamaks and stellarators are compared.

Volkov, E.D.; Perepelkin, N.F.; Suprunenko, V.A.; Arsen'ev, A.V.; Burchenko, P.Y.; Vasil'ev, M.P.; Kotsubanov, V.D.; Kulaga, A.E.; Rubtsov, K.S.; Slavnyi, A.S.

1984-07-01

43

Anomalous transport in toroidal plasmas. Final progress report  

SciTech Connect

Anomalous transport in toroidal plasmas arises from the presence of more complicated magnetic and electric fields than are required by the macroscopic equilibrium of the plasma. If one knew these fields, then the transport coefficients, calculated by classical methods, would be correct except for the direct transport of energy by fields (which is usually considered negligible). The limitation of this procedure is the lack of knowledge of the field perturbations, but there are a number of features that are generally accepted whether the perturbations are due to microinstabilities or due to macroscopic effects such as tearing modes. In particular, the frequencies and the wave numbers of perturbations satisfy {omega}* {approx_lt} {omega}, k{sub {perpendicular}} {rho}{sub i} {approx_lt} 1, and k{sub {parallel}} {rho}{sub i} {much_lt} 1 which imply that the magnetic moments of both the ions and the electrons are conserved and that the particle trajectories obey drift equations. The drift equations imply that if magnetic surfaces exist, particles can cross a surface only if there is a spatial variation in the field strength or the electric potential in the surface. If surfaces fail to exist, then particles can also cross the toroidal flux surfaces by moving along the field lines. Here the authors develop Monte Carlo codes to study anomalous transport in ZT-40 and TOKAPOLE 2.

Punjabi, A.

1992-12-31

44

The Effects of Weak Collisions on Nonlinear Plasma Kinetics  

NASA Astrophysics Data System (ADS)

Kinetic plasma behaviors have long been of interest to those studying space and laboratory plasmas. For instance, kinetic plasma instabilities are widely believed to be responsible for the generation of anomalous resistivity in reconnection layers, providing a possible mechanism for fast reconnection. The concept of Landau damping is fundamental to such wave kinetic instabilities in space, and is treated typically within the framework of the collisionless Vlasov equation. It has become clear in recent theoretical and experimental work that weak collisions are a singular perturbation on the collisionless theory, and qualitatively alter the results of the collisionless theory. In particular, it has been demonstrated by C. S. Ng, A. Bhattacharjee, and F. Skiff that the Case-Van Kampen continuous spectrum, which are the underlying eigenmodes of the collisionless system, are completely eliminated and replaced by a discrete spectrum (hereafter referred to as the NBS spectrum). The NBS spectrum includes Landau-damped roots as exact eigenmodes, but is significantly broader, including a larger spectrum of discrete roots. We discuss the implications of these results for two nonlinear applications, the plasma wave echo and the ion acoustic instability, by means of a new Vlasov code that has been modified to include the Lenard-Bernstein collision operator. We show that the existing collisional theories for the echo, which fail to account for the discrete collisional spectrum, come close, but do not quite yield the appropriate collisional damping rates. Of greater practical importance to problems involving dissipation and anomalous transport is the generation of anomalous resistivity due to microinstabilities. As a specific example, we consider the ion acoustic wave. We compare our numerical findings with the anomalous resistivity estimates of A. Galeev and R. Z. Sagdeev for both collisionless and weakly collisional systems. In the regime of applicability of the theoretical estimates, the agreement is good within an order of magnitude.

Black, Carrie E.

45

Currents between tethered electrodes in a magnetized laboratory plasma  

SciTech Connect

Laboratory experiments on important plasma physics issues of electrodynamic tethers are performed. These include current propagation, formation of wave wings, limits of current collection, nonlinear effects and instabilities, charging phenomena, and characteristics of transmission lines in plasmas. The current system is established with a small electron-emitting hot cathode tethered to an electron-collecting anode, both movable across the magnetic field and energized by potential differences up to V {approx} 100 kT{sub e}/e. The total current density in space and time is obtained from complete measurements of the perturbed magnetic field. J = {gradient} {times} B(r,t)/{mu}{sub 0}. The fast spacecraft motion is reproduced in the laboratory by moving the tethered electrodes in small increments, applying delayed current pulses, and reconstructing the net field by a linear superposition of locally emitted wavelets. With this technique, the small-amplitude dc current pattern is shown to form whistler wings at each electrode instead of the generall accepted Alfven wings. For the beam electrode, the whistler wing separates from the field-aligned beam which carries no net current. Large-amplitude return currents to a stationary anode generate current-driven microinstabilities, parallel electric fields, ion depletions, current disruptions, and time-varying electrode charging. At appropriately high potentials and neutral densities, excess neutrals are ionized near the anode. The anode sheath emits high-frequency electron transit-time oscillations at the sheath-plasma resonance. The beam generates Langmuir turbulence, ion sound turbulence, electron heating, space charge fields, and Hall currents. An insulated, perfectly conducting transmission line embedded in the plasma becomes lossy due to excitation of whistler waves and magnetic field diffusion effects.

Stenzel, R.L.; Urrutia, J.M. (Univ. of California, Los Angeles (United States))

1990-05-01

46

Unified fluid/kinetic description of magnetized plasmas  

SciTech Connect

Unified fluid/kinetic equations for the plasma perturbed density ({tilde n}), parallel flow velocity ({tilde u}{sub {parallel}}) and temperature ({tilde T}) are developed in a sheared slab geometry by calculating the fluid moment closure relations kinetically. At first, a set of (unclosed) nonlinear perturbed fluid equations for {tilde n}, {tilde u}{sub {parallel}} and {tilde T} is developed using a drift ordering analysis and a new gyroviscous force ({del} {center dot} {product}{sub g}). Thereafter, to develop linear closure relations for b {center dot} {del} {center dot} {tilde product}{sub {parallel}} and {tilde q}{sub {parallel}}, a drift-kinetic version of a Chapman-Enskog-like (CEL) equation is developed and solved by using a moment approach and a physically realistic collision operator (Lorentz scattering operator plus the momentum restoring terms.) The resultant closure relations for b {center dot} {del} {center dot} {tilde product}{sub {parallel}} and {tilde q}{sub {parallel}} unify both the fluid and kinetic approaches. In the collisional fluid limit the equations reduce to the well-known Braginskii equations. In the adiabatic limit they reproduce the usual kinetic results, including Landau damping. It is shown that the CEL approach is more compatible with a fluid-like description of plasmas than the usual drift/gyro kinetic approach. A remarkable simplification of these complicated closure relations is achieved by using single power of plasma dispersion functions with modified arguments. The results are compared with other recently developed Landau damping models and shown to be more accurate, complete and physically meaningful. The resultant set of nonlinear fluid/kinetic equations (with linear closure relations) will be applied to various microinstabilities in tokamak plasmas and drift type microturbulence in a separate paper. 19 refs., 7 refs., 1 tab.

Chang, Zuoyang; Callen, J.D.

1991-06-01

47

Unified fluid/kinetic description of magnetized plasmas  

NASA Astrophysics Data System (ADS)

The unified fluid/kinetic equations developed in part 1 of this work are used to study plasma drift type microinstabilities. A generalized perturbed Ohm's law derived which is uniformly valid for arbitrary collisionality omega/nu and adiabaticity omega/k(parallel) upsilon(sub t). For electron drift waves we demonstrate that the collisional and collisionless drift wave instabilities can be uniformly described by replacing the Spitzer resistivity with a generalized pseudo-resistivity. Similarly, for ion drift type modes we obtain a uniformly valid dispersion relation for the ion temperature gradient modes (eta(sub i) modes). The eta(sub i) threshold as a function of ion-ion collisionality and ion Landau damping strength is addressed. Applying the unified equations to electron electromagnetic modes leads to generalized coupled equations for tilde phi and tilde A(parallel) which include electron Landau damping effects and are valid for any omega/nu. It is shown that the semi-collisional micro-tearing and drift-tearing modes of Drake and Lee can be easily reproduced in the appropriate limit. Generalization of the two-field Hasegawa-Wakatani turbulent equations to include electron temperature fluctuations and linear Landau damping effects is also discussed. Finally, a new method is presented to facilitate the study of magnetic trapped particle modes using our kinetic closure procedure. It is found that by including the trapped particle effects in the closure relations, the usual separation of the fluid equations into trapped and untrapped components becomes unnecessary.

Chang, Zuoyang; Callen, J. D.

1991-07-01

48

Sheared Rotation Effects on Kinetic Stability in Enhanced Confinement Tokamak Plasmas, and Nonlinear Dynamics of Fluctuations and Flows in Axisymmetric Plasmas  

SciTech Connect

Sheared rotation dynamics are widely believed to have significant influence on experimentally observed confinement transitions in advanced operating modes in major tokamak experiments, such as the Tokamak Fusion Test Reactor (TFTR) with reversed magnetic shear regions in the plasma interior. The high-n toroidal drift modes destabilized by the combined effects of ion temperature gradients and trapped particles in toroidal geometry can be strongly affected by radially sheared toroidal and poloidal plasma rotation. In previous work with the FULL linear microinstability code, a simplified rotation model including only toroidal rotation was employed, and results were obtained. Here, a more complete rotation model, that includes contributions from toroidal and poloidal rotation and the ion pressure gradient to the total radial electric field, is used for a proper self-consistent treatment of this key problem. Relevant advanced operating mode cases for TFTR are presented. In addition, the complementary problem of the dynamics of fluctuation-driven E x B flow is investigated by an integrated program of gyrokinetic simulation in annulus geometry and gyrofluid simulation in flux tube geometry.

Rewoldt, G.; Beer, M.A.; Chance, M.S.; Hahm, T.S.; Lin, Z.; Tang, W.M. [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States)

1997-12-01

49

Sheared Rotation Effects on Kinetic Stability in Enhanced Confinement Tokamak Plasmas, and Nonlinear Dynamics of Fluctuations and Flows in Axisymmetric Plasmas  

SciTech Connect

Sheared rotation dynamics are widely believed to have signficant influence on experimentally observed confinement transitions in advanced operating modes in major tokamak experiments, such as the Tokamak Fusion Test Reactor (TFTR) [D.J. Grove and D.M. Meade, Nuclear Fusion 25, 1167 (1985)], with reversed magnetic shear regions in the plasma interior. The high-n toroidal drift modes destabilized by the combined effects of ion temperature gradients and trapped particles in toroidal geometry can be strongly affected by radially sheared toroidal and poloidal plasma rotation. In previous work with the FULL linear microinstability code, a simplified rotation model including only toroidal rotation was employed, and results were obtained. Here, a more complete rotation model, that includes contributions from toroidal and poloidal rotation and the ion pressure gradient to the total radial electric field, is used for a proper self-consistent treatment of this key problem. Relevant advanced operating mode cases for TFTR are presented. In addition, the complementary problem of the dynamics of fluctuation-driven E x B flow is investigated by an integrated program of gyrokinetic simulation in annulus geometry and gyrofluid simulation in flux tube geometry.

Beer, M.A.; Chance, M.S.; Hahm, T.S.; Lin, Z.; Rewoldt, G.; Tang, W.M.

1997-11-01

50

Sheared rotation effects on kinetic stability in enhanced confinement tokamak plasmas, and nonlinear dynamics of fluctuations and flows in axisymmetric plasmas  

NASA Astrophysics Data System (ADS)

Sheared rotation dynamics are widely believed to have significant influence on experimentally-observed confinement transitions in advanced operating modes in major tokamak experiments, such as the Tokamak Fusion Test Reactor (TFTR) [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)], with reversed magnetic shear regions in the plasma interior. The high-n toroidal drift modes destabilized by the combined effects of ion temperature gradients and trapped particles in toroidal geometry can be strongly affected by radially-sheared toroidal and poloidal plasma rotation. In previous work with the FULL linear microinstability code, a simplified rotation model including only toroidal rotation was employed, and results were obtained. Here, a more complete rotation model, which includes contributions from toroidal and poloidal rotation and the ion pressure gradient to the total radial electric field, is used for a proper self-consistent treatment of this key problem. Relevant advanced operating mode cases for TFTR are presented. In addition, the complementary problem of the dynamics of fluctuation-driven E×B flow is investigated by an integrated program of gyrokinetic simulation in annulus geometry and gyrofluid simulation in flux tube geometry.

Rewoldt, G.; Beer, M. A.; Chance, M. S.; Hahm, T. S.; Lin, Z.; Tang, W. M.

1998-05-01

51

High sensitivity, inductively coupled miniature magnetic probe array for detailed measurement of time varying magnetic field profiles in plasma flows  

SciTech Connect

A modified {dot {ital B}} circuit design has been implemented as part of a miniature magnetic probe array for the Coaxial Plasma Source experiment [R. M. Mayo {ital et} {ital al}., Plasma Sources Sci. Technol. {bold 4}, 47 (1995)] at the North Carolina State University. This facility is currently being used for the generation of energetic plasma flows to allow laboratory study of magnetogasdynamics with particular emphasis on the importance of the Hall effect [D. C. Black {ital et} {ital al}., Phys. Plasma {bold 1}, 3115 (1994)] and plasma microinstabilities [R. M. Mayo {ital et} {ital al}., Phys. Plasma {bold 2}, 337 (1995)] to plasma transport in coaxial plasma sources. The miniature magnetic probe array consists of ten spatially separated coils wound on an Acetal form of dimensions 2.38 cm by 0.32 cm by 0.32 cm. At five positions, with roughly 0.32 cm separation, two mutually perpendicular coils are wound to measure the magnetic field in the {cflx {theta}} and {cflx {ital z}} directions. The modification to the signal processing circuitry consists of the use of a step-up transformer to boost the probe signal prior to filtering and acquiring the signal at the data acquisition system. This additional means of amplifying the signal allows for reduction in the size of the probe, and thus helps minimize the perturbing effect of the magnetic probe on the plasma. An additional advantage of using a signal transformer is that it provides electrical isolation between the experiment and the data acquisition system. {copyright} {ital 1996 American Institute of Physics.}

Black, D.C.; Mayo, R.M. [Department of Nuclear Engineering, North Carolina State University, Raleigh, North Carolina 27695-7909 (United States)

1996-04-01

52

Numerical simulations of anisotropic plasmas using a modified ZEUS-MP  

NASA Astrophysics Data System (ADS)

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.

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

2012-10-01

53

Plasma turbulence  

SciTech Connect

The origin of plasma turbulence from currents and spatial gradients in plasmas is described and shown to lead to the dominant transport mechanism in many plasma regimes. A wide variety of turbulent transport mechanism exists in plasmas. In this survey the authors summarize some of the universally observed plasma transport rates.

Horton, W. [Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies; Hu, G. [Globalstar LP, San Jose, CA (United States)

1998-07-01

54

Dusty plasmas  

Microsoft Academic Search

The properties of dusty plasmas — low-temperature plasmas containing charged macroparticles — are considered. The most important elementary processes in dusty plasmas and the forces acting on dust particles are investigated. The results of experimental and theoretical investigations of different states of strongly nonideal dusty plasmas — crystal-like, liquid-like, gas-like — are summarized. Waves and oscillations in dusty plasmas, as

Vladimir E Fortov; Aleksei G Khrapak; Sergei A Khrapak; Vladimir I Molotkov; Oleg F Petrov

2004-01-01

55

Plasma jets and plasma bullets  

Microsoft Academic Search

Plasma plumes, or plasma jets, belong to a large family of gas discharges whereby the discharge plasma is extended beyond the plasma generation region into the surrounding ambience, either by a field (e.g. electromagnetic, convective gas flow, or shock wave) or a gradient of a directionless physical quantity (e.g. particle density, pressure, or temperature). This physical extension of a plasma

M G Kong; B N Ganguly; R F Hicks

2012-01-01

56

PLASMA GENERATOR  

DOEpatents

This patent describes apparatus for producing an electricity neutral ionized gas discharge, termed a plasma, substantially free from contamination with neutral gas particles. The plasma generator of the present invention comprises a plasma chamber wherein gas introduced into the chamber is ionized by a radiofrequency source. A magnetic field is used to focus the plasma in line with an exit. This magnetic field cooperates with a differential pressure created across the exit to draw a uniform and uncontaminated plasma from the plasma chamber.

Foster, J.S. Jr.

1958-03-11

57

Numerical analysis of the impact of the ion threshold, ion stiffness and temperature pedestal on global confinement and fusion performance in JET and in ITER plasmas  

NASA Astrophysics Data System (ADS)

Understanding the impact of micro-instabilities on the global plasma performance is essential in order to make realistic predictions for relevant tokamak scenarios. The semi-empirical transport model CGM is a useful tool to this scope because it depends explicitly on the threshold and the stiffness level, two key parameters of turbulent transport as driven by the ITG/TEM instabilities. The CGM then makes it possible to vary separately the transport variables and to see the quantitative effect of their changes on the global plasma performance. This paper focuses on the impact that four parameters (ion temperature gradient threshold, ion temperature gradient stiffness, height of the temperature pedestal and input power) have individually on the global confinement. Parameters for JET hybrid plasmas and prospective ITER plasmas are used. For JET plasmas changing the ion temperature gradient stiffness from typical low values (characterized by ?s = 0.1) to high values (?s = 2) leads to variations in the H factor up to 30%. Varying the ion temperature gradient threshold within the interval of the realistic values 3-7 causes changes in H98 between 20% and 30%. The effect of the temperature pedestal height is very considerable (over 50% of H98 variation changing the temperature pedestal height from 1 to 3 keV), in agreement with the previous investigations. H98 is found to slightly decrease with increasing power (from 20 to 60 MW of injected NBI power) for high stiffness and to remain constant in the case of low stiffness. For ITER plasmas the variation of the H factor has qualitatively similar trends, but the variations with respect to changes in stiffness and threshold are smaller. However, very important changes are found for the values predicted by the fusion power in these plasmas.

Baiocchi, B.; Mantica, P.; Tala, T.; Corrigan, G.; Joffrin, E.; Kirov, K.; Naulin, V.; contributors, JET-EFDA

2012-08-01

58

Plasma Medicine  

NASA Astrophysics Data System (ADS)

Foreword R. Satava and R. J. Barker; Part I. Introduction to Non-equilibrium Plasma, Cell Biology, and Contamination: 1. Introduction M. Laroussi; 2. Fundamentals of non-equilibrium plasmas M. Kushner and M. Kong; 3. Non-equilibrium plasma sources M. Laroussi and M. Kong; 4. Basic cell biology L. Greene and G. Shama; 5. Contamination G. Shama and B. Ahlfeld; Part II. Plasma Biology and Plasma Medicine: 6. Common healthcare challenges G. Isbary and W. Stolz; 7. Plasma decontamination of surfaces M. Kong and M. Laroussi; 8. Plasma decontamination of gases and liquids A. Fridman; 9. Plasma-cell interaction: prokaryotes M. Laroussi and M. Kong; 10. Plasma-cell interaction: eukaryotes G. Isbary, G. Morfill and W. Stolz; 11. Plasma based wound healing G. Isbary, G. Morfill and W. Stolz; 12. Plasma ablation, surgery, and dental applications K. Stalder, J. Woloszko, S. Kalghatgi, G. McCombs, M. Darby and M. Laroussi; Index.

Laroussi, M.; Kong, M. G.; Morfill, G.; Stolz, W.

2012-05-01

59

Plasma electronics  

Microsoft Academic Search

The paper reviews the main directions and achievements in plasma electronics research in the U.S.S.R. This research encompasses fundamental plasma investigations, the wave and oscillatory properties of plasmas, various instabilities, and turbulence in plasmas, with the purpose of achieving significant increases in the limiting currents, powers, and energies of beams as compared with the limits of vacuum technology. Aspects of

Ia. B. Fainberg

1978-01-01

60

Properties of large scale plasma flow during the early stage of the plasmaspheric refilling  

SciTech Connect

Ion continuity, momentum and energy equations were solved for the plasma flow along the closed magnetic field lines. During the initial stage of the supersonic outflow in the equatorial region, the ions cool substantially. Using the hydrodynamic model for the large-scale plasma flow, the dynamics of shocks was examined which form in the geomagnetic flux tubes during the early stages of refilling. These shocks are more like those forming in neutral gases than the electrostatic shocks driven by microinstabilities involving ion-ion interaction. Therefore, the shocks seen in the hydrodynamic model are termed as hydrodynamic shocks. Such shocks are generally unsteady and therefore the usual shock jump conditions given by Rankine-Hugoniot relations are not strictly applicable to them. The density, flow velocity and temperature structures associated with the shocks are examined for both asymmetrical and symmetrical flows. In the asymmetrical flow the outflow from one of two conjugate ionospheres is dominant. On the other hand, in the symmetrical case outflows from the two ionospheric sources are identical. Both cases are treated by a two-stream model. In the late type of flow, the early-time refilling shows a relaxation type of oscillation, which is driven by the large-scale interactions between the two identical streams. After this early stage, the resulting temperature structure shows some interesting features. In the equatorial region the streams are isothermal, but in the off-equatorial regions the streams have quite different temperatures, and also densities and flow velocities. The dense and slow stream is found to be warmer than the low-density fast stream. In the late stage of refilling, the temperature is found to steadily increase from the c

Singh, N.; Craven, P.; Torr, D.G.; Richards, P.G.

1990-01-01

61

Dusty plasmas  

Microsoft Academic Search

Dust grains immersed in plasma become charged. The charge is determined by the plasma characteristics, by secondary and photoemission from the grain, by grain velocity, and at any given instant by the past time history of the charging currents. This charge affects the Coulomb drag on a grain moving through the plasma. It affects the motion of the grain in

T G Northrop

1992-01-01

62

Plasma Physics  

Microsoft Academic Search

Beginning at an introductory level, this text presents a thorough treatment of plasma physics, including an extensive discussion of its applications in thermonuclear fusion research. A novel feature of this book is its comprehensive description of the various concepts and formulas widely used in fusion theory based on the fundamental equations of the plasma fluid. The physics of fusion plasmas

Kyoji Nishikawa; Masashiro Wakatani

1990-01-01

63

Plasma accelerators  

SciTech Connect

In this paper we discuss plasma accelerators which might provide high gradient accelerating fields suitable for TeV linear colliders. In particular we discuss two types of plasma accelerators which have been proposed, the Plasma Beat Wave Accelerator and the Plasma Wake Field Accelerator. We show that the electric fields in the plasma for both schemes are very similar, and thus the dynamics of the driven beams are very similar. The differences appear in the parameters associated with the driving beams. In particular to obtain a given accelerating gradient, the Plasma Wake Field Accelerator has a higher efficiency and a lower total energy for the driving beam. Finally, we show for the Plasma Wake Field Accelerator that one can accelerate high quality low emittance beams and, in principle, obtain efficiencies and energy spreads comparable to those obtained with conventional techniques.

Ruth, R.D.; Chen, P.

1986-03-01

64

Thermal plasmas  

Microsoft Academic Search

Although many thermal plasma processes have been developed for industrial applications, the wide acceptance as a manufacturing technology is prevented due to economical and competitive reasons, and\\/or reproducibility and reliability aspects. This paper is devoted to an assessment of the present knowledge in the following topics: (1) plasma torch and performance of blown arc (dc or ac), transferred arc and

P. Fauchais; A. Vardelle

1997-01-01

65

Plasma valve  

DOEpatents

A plasma valve includes a confinement channel and primary anode and cathode disposed therein. An ignition cathode is disposed adjacent the primary cathode. Power supplies are joined to the cathodes and anode for rapidly igniting and maintaining a plasma in the channel for preventing leakage of atmospheric pressure through the channel.

Hershcovitch, Ady (Mount Sinai, NY); Sharma, Sushil (Hinsdale, IL); Noonan, John (Naperville, IL); Rotela, Elbio (Clarendon Hills, IL); Khounsary, Ali (Hinsdale, IL)

2003-01-01

66

Global simulation of edge pedestal micro-instabilities  

NASA Astrophysics Data System (ADS)

We study micro turbulence of the tokamak edge pedestal with global gyrokinetic particle simulations. The simulation code GEM is an electromagnetic ? code. Two sets of DIII-D experimental profiles, shot #131997 and shot #136051 are used. The dominant instabilities appear to be two kinds of modes both propagating in the electron diamagnetic direction, with comparable linear growth rates. The low n mode is at the Alfven frequency range and driven by density and ion temperature gradients. The high n mode is driven by electron temperature gradient and has a low real frequency. A ? scan shows that the low n mode is electromagnetic. Frequency analysis shows that the high n mode is sometimes mixed with an ion instability. Experimental radial electric field is applied and its effects studied. We will also show some preliminary nonlinear results.

Wan, Weigang; Parker, Scott; Chen, Yang

2011-11-01

67

Simulating gyrokinetic microinstabilities in stellarator geometry with GS2  

SciTech Connect

The nonlinear gyrokinetic code GS2 has been extended to treat non-axisymmetric stellarator geometry. Electromagnetic perturbations and multiple trapped particle regions are allowed. Here, linear, collisionless, electrostatic simulations of the quasi-axisymmetric, three-field period national compact stellarator experiment (NCSX) design QAS3-C82 have been successfully benchmarked against the eigenvalue code FULL. Quantitatively, the linear stability calculations of GS2 and FULL agree to within {approx}10%.

Baumgaertel, J. A.; Guttenfelder, W.; Hammett, G. W.; Mikkelsen, D. R.; Rewoldt, G.; Tang, W. M. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Belli, E. A. [General Atomics, San Diego, California 92186 (United States); Dorland, W. [Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Xanthopoulos, P. [Max-Planck-Institut fuer Plasmaphysik, D-17491 Greifswald (Germany)

2011-12-15

68

The plasma condensation: Liquid and crystalline plasmas  

Microsoft Academic Search

Colloidal plasmas may ``condense'' under certain conditions into liquid and crystalline states, while retaining their essential plasma properties. This ``plasma condensation'' therefore leads to new states of matter: ``liquid plasmas'' and ``plasma crystals.'' The experimental discovery was first reported in 1994, and since then many researchers have begun to investigate the properties of condensed plasma states. In this paper we

G. E. Morfill; H. M. Thomas; U. Konopka; M. Zuzic

1999-01-01

69

The plasma condensation: Liquid and crystalline plasmas  

Microsoft Academic Search

Colloidal plasmas may “condense” under certain conditions into liquid and crystalline states, while retaining their essential plasma properties. This “plasma condensation” therefore leads to new states of matter: “liquid plasmas” and “plasma crystals.” The experimental discovery was first reported in 1994, and since then many researchers have begun to investigate the properties of condensed plasma states. In this paper we

G. E. Morfill; H. M. Thomas; U. Konopka; M. Zuzic

1999-01-01

70

Plasma Separation.  

National Technical Information Service (NTIS)

This process employs a thermal plasma for the separation and production of oxygen and metals. It is a continuous process that requires no consumables and relies entirely on space resources. The almost complete absence of waste renders it relatively clean....

W. Steurer

1992-01-01

71

Plasma Generation  

Microsoft Academic Search

\\u000a Lightnings and technical plasmas are generated by an electric breakdown in a gas. The ignition process leads to a subsequent\\u000a current flow that generates an electrical discharge. Depending on the power source that feeds the plasma, we distinguish direct\\u000a current (dc), low-frequency alternating current (ac), and radio-frequency (rf) discharges. This chapter gives a brief introduction\\u000a into the most common types

Alexander Piel

72

PLASMA DEVICE  

DOEpatents

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

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

1961-12-26

73

Sheared rotation effects on kinetic stability in enhanced confinement tokamak plasmas, and nonlinear dynamics of fluctuations and flows in axisymmetric plasmas  

NASA Astrophysics Data System (ADS)

Sheared rotation dynamics are widely believed to have significant influence on experimentally-observed confinement transitions in advanced operating modes in major tokamak experiments, such as DIII-D and TFTR with reversed magnetic shear regions in the plasma interior, or the VH-mode or high-li H-mode for DIII-D. The high-n toroidal instabilities destabilized by the combined effects of ion temperature gradients and trapped particles in toroidal geometry can be strongly affected by radially-sheared toroidal and poloidal plasma rotation. In previous work with the FULL linear microinstability code, a simplified rotation model including only toroidal rotation was employed, and results were obtained for DIII-D and TFTR. However, a more complete rotation model, that includes contributions from toroidal and poloidal rotation and the ion pressure gradient to the total radial electric field, is needed for a proper self-consistent treatment of this key problem. Both models result in additional stabilizing or destabilizing drifts added to the normal magnetic drifts. Specifically, this new model is capable of including effects of the E × B shearing, written in terms of equilibrium quantities, ?E ~= |[(R B_?)^2 / B] d/d? (E_r/RB_?)|, on an equal basis with the other rotation model terms in the linear instability calculation. All of the rotation terms are now evaluated for a numerically-calculated flux-coordinate MHD equilibrium with magnetic surfaces of arbitrary cross-sectional shape and aspect ratio. Needed Er levels for marginal stability with this approach will be compared with corresponding levels from the heuristic stabilization criterion ?E ~ ?, as observed in ITG simulations, where ? is the linear growth rate without rotation effects, which has sometimes shown good correlations with experimental transitions. Relevant advanced operating mode cases for DIII-D, TFTR, JET, JT-60U, and NSTX will be presented. In addition, the complementary problem of the dynamics of fluctuation-driven E × B flow is investigated by an integrated program of analytic nonlinear theory, gyrokinetic simulation in annulus geometry, and gyrofluid simulation in flux tube geometry. New three-dimensional global gyrokinetic simulations systematically including both collisional and turbulent transport contributions will help assess the validity regimes for estimates of poloidal rotation damping and buildup. The flow dynamics is studied kinetically via a high-order Lie-perturbative analysis of the bounce-averaged Vlasov and Poisson equations.

Rewoldt, G.

1997-11-01

74

Plasma technology  

SciTech Connect

This paper describes the uses of plasma technology for the thermal destruction of hazardous wastes such as PCBs, dioxins, hydrocarbons, military chemicals and biological materials; for metals recovery from steel making dusts. One advantage of the process is that destruction of wastes can be carried out on site. Systems in several countries use the excess thermal energy for district heating.

Herlitz, H.G.

1986-11-01

75

Plasma generator  

SciTech Connect

A plasma generator comprises a discharge chamber provided with a means for introducing a plasma-forming medium and associated with a cathode assembly and an anode assembly. The latter includes at least two plasmatrons each having a hole for an inlet for the plasma-forming medium and being provided with an end electrode and an auxiliary hollow electrode. These electrodes are connected to an arc discharge initiating system. The exit openings of the auxiliary electrodes communicate with the discharge chamber and are evenly distributed along the perimeter of its cross section. The cathode assembly comprises at least two plasmatrons each having an inlet for the plasma-forming medium and being provided with an end electrode and an auxiliary hollow electrode. Both electrodes are connected to an arc discharge initiating system. In addition, the end electrodes are connected to the power supply. The exit openings of the auxiliary electrodes communicate with the discharge chamber and are evenly distributed along the perimeter of its cross section. The diameter of each exit opening of the auxiliary electrode of each plasmatron of each assembly, both cathode and anode, is selected to satisfy a specific relationship.

Anshakov, A.S.; Khudyakov, G.N.; Lytkin, A.Y.; Zhukov, M.F.

1982-09-28

76

Plasma accelerators; Plazmennye uskoriteli  

Microsoft Academic Search

Papers concerning the physical processes in plasma accelerators are ; included, covering some specific accelerator types, magnetic plasma compressors, ; plasma diagnostics methods, and plasma accelerator applications in thermonuclear ; studies, gasdynamics, and space studies. The topics also include plasma ; acceleration control problems, high-vacuum technology, plasma accelerator designs ; with narrow and broad acceleration zones, and electrode processes in

Artsimovich

1973-01-01

77

Selective plasma etching  

NASA Astrophysics Data System (ADS)

Plasma etching of silicon nitride glassivation layers on silicon dice using CF4 was successfully carried out with a commercial plasma etcher. The parameters of power level and partial pressure gas were downscaled from the commercial plasma etcher to a bench-top plasma etcher. Plasma etching of silicon nitride was successfully performed in the bench-top plasma etcher.

Franti, G. W.

1991-12-01

78

Plasmas Assessment  

NSDL National Science Digital Library

This brief assessment on Plasmas is intended to be used after students have completed the introductory activity on the topic, which may be located here. The assessment consists of 10 multiple choice and short answer questions. The other educational modules in this series can be found here. Instructors and students are encouraged to sign up with the Electron Technologies site here before starting to use these materials.

2012-10-02

79

Kinetic theory of plasma waves, homogeneous plasmas  

Microsoft Academic Search

The linear theory of plasma waves in homogeneous plasma is arguably the most mature and best understood branch of plasma physics. Given the recently revised version of Stix's excellent Waves in Plasmas (1992), one might ask whether another book on this subject is necessary only a few years later. The answer lies in the scope of this volume; it is

Miklos Porkolab

1998-01-01

80

Surface Plasma Sources with Helicon Plasma Generators  

SciTech Connect

A Surface Plasma Source (SPS) with plasma generation by a saddle type antenna is discussed. The following features of the helicon discharge with a saddle type antenna in magnetic field are identified: efficient plasma generation in resonant condition, low gas density, strong separation of plasma from the wall, possibility to control plasma flux distribution by magnetic field configuration. Applications of saddle type antenna in SPS for accelerators for Homeland Security and for Neutral Beam Injectors (NBI) are considered.

Dudnikov, Vadim; Dudnikova, Galina; Farrell, J. Paul [Brookhaven Technology Group, Inc., Setauket, NY (United States)

2007-08-10

81

The Plasma Condensation - Liquid Plasmas and Plasma Crystals  

Microsoft Academic Search

Plasmas - ionised gases - are usually regarded as totally disordered many-particle systems. Cooling them leads to recombination and then condensation. However, it was shown in 1994 that certain types of plasmas, the so-called \\

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

1998-01-01

82

Plasma Kinetics  

NASA Astrophysics Data System (ADS)

In Chapter 7 of ISSI SR-001, Schwartz et al. [1998] explain the basic ideas of analysis by means of plasma kinetics: Liouville mapping and finite gyroradius effects. Liouville mapping can be used to relate features of distribution functions such as heating, anisotropies or beams, to the field variations. It is based on the conservation of phase space density along particle trajectories in collisionless plasmas, and therefore requires that particle trajectories (or at least their initial and final states) can be accurately approximated. This requirement generally relies on invariants of the particle motion such as the energy and adiabatic invariants and some knowledge of the electromagnetic fields along the trajectories. The large gyroradius of energetic ions has the consequence that ions detected at different directions are actually probing conditions at considerable distances around the space- craft. Density gradients then appear as gyrophase anisotropies in the angular distributions. This effect was first employed by Kaufmann and Konradi [1973] to probe the magnetopause. Section 7.5 of Schwartz et al. [1998] explain how it can be used to remotely sense sharp boundaries in ion densities. In particular, see Figures 7.4 and 7.6 in that chapter for a graphical demonstration. For a historical perspective on these topics, see also the classic paper by Northrop and Teller [1960] on the motion of charged particles in the Earth's magnetic field. In addition, Whipple et al. [1998] present an alternative framework that builds on the underlying concepts, while Whipple et al. [1986] describe extensions to the classic adiabatic theory that apply even in regions of strong gradients.

Daly, Patrick W.; Schwartz, Steven J.; Lefebvre, Betrand

83

Plasma Dictionary Website  

NASA Astrophysics Data System (ADS)

In response to many inquiries for a list of plasma terms, a database driven Plasma Dictionary website (plasmadictionary.llnl.gov) was created that allows users to submit new terms, search for specific terms or browse alphabetic listings. The Plasma Dictionary website contents began with the Fusion & Plasma Glossary terms available at the Fusion Energy Educational website (fusedweb.llnl.gov). Plasma researchers are encouraged to add terms and definitions. By clarifying the meanings of specific plasma terms, it is envisioned that the primary use of the Plasma Dictionary website will be by students, teachers, researchers, and writers for (1) Enhancing literacy in plasma science, (2) Serving as an educational aid, (3) Providing practical information, and (4) Helping clarify plasma writings. The Plasma Dictionary website has already proved useful in responding to a request from the CRC Press (www.crcpress.com) to add plasma terms to its CRC physics dictionary project (members.aol.com/physdict/).

Correll, Don; Heeter, Robert; Alvarez, Mitch

2000-10-01

84

Plasma Behavior in a Plasma Gun Jet  

NASA Astrophysics Data System (ADS)

Plasma guns will provide initial pre-ionized plasma for a field reversed configuration experiment (FRX-L). The development and testing of these guns is being carried out on the Reconnection Scaling experiment (RSX). Successful gun operation requires the ionized plasma leaving the guns to be maximized and the neutral gas particles surrounding each gun jet to be minimized. A fast ionization gauge (FIG) produced by Applied Pulsed Power, Inc. with a response time of >20 mTorr/?s will be used to measure the density of hydrogen plasma in the RSX in order to determine the shape of the plasma pulse and the speed of the particles. Additionally, the FIG will provide data to calculate the quantity of gas particles preceding the plasma jet and a Mach number of the plasma leaving the gun. An equation of state fluid model will be used for the system and to compare calculations with experimental data.

Pulliam, Daniel; Intrator, Thomas; Adams, Colin; Sears, Jason; Weber, Thomas

2011-11-01

85

Dust-Plasma  

SciTech Connect

Our theoretical research on dust-plasma interactions has concentrated on three main areas: a)studies of grain charging and applications; b) waves and instabilities in weakly correlated dusty plasma with applications to space and laboratory plasmas; c) waves in strongly coupled dusty plasmas.

Marelene Rosenberg

2005-02-22

86

The plasma universe  

Microsoft Academic Search

The extrapolation of observed plasma densities, magnetic and electric field strengths, and energies in near-Earth and solar system plasmas to regions beyond the reach of spacecraft has led to the concept of a plasma universe. The importance of applying electromagnetism and plasma physics to the problem of radiogalaxy, galaxy, and star formation derives from the fact that the Universe is

A. L. Peratt

1989-01-01

87

Thermal plasma processing  

Microsoft Academic Search

A review is given of the fundamental aspects involved in material processing using thermal plasma technology. The description of plasma generating devices covers DC plasma torches, DC transferred arcs, RF inductively coupled plasma torches and hybrid combinations of them. Emphasis is given to the identification of the basic energy coupling mechanism in each case and the principal characteristics of the

Maher I. Boulos

1991-01-01

88

Modelling of Complex Plasmas  

Microsoft Academic Search

Nowadays plasmas are used for various applications such as the fabrication of silicon solar cells, integrated circuits, coatings and dental cleaning. In the case of a processing plasma, e.g. for the fabrication of amorphous silicon solar cells, a mixture of silane and hydrogen gas is injected in a reactor. These gases are decomposed by making a plasma. A plasma with

M. R. Akdim

2003-01-01

89

Plasma sweeper. [Patents  

DOEpatents

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

Motley, R.W.; Glanz, J.

1982-10-25

90

Plasmas for space propulsion  

NASA Astrophysics Data System (ADS)

Plasma thrusters are challenging the monopoly of chemical thrusters in space propulsion. The specific energy that can be deposited into a plasma beam is orders of magnitude larger than the specific chemical energy of known fuels. Plasma thrusters constitute a vast family of devices ranging from already commercial thrusters to incipient laboratory prototypes. Figures of merit in plasma propulsion are discussed. Plasma processes and conditions differ widely from one thruster to another, with the pre-eminence of magnetized, weakly collisional plasmas. Energy is imparted to the plasma via either energetic electron injection, biased electrodes or electromagnetic irradiation. Plasma acceleration can be electrothermal, electrostatic or electromagnetic. Plasma-wall interaction affects energy deposition and erosion of thruster elements, and thus is central for thruster efficiency and lifetime. Magnetic confinement and magnetic nozzles are present in several devices. Oscillations and turbulent transport are intrinsic to the performances of some thrusters. Several thrusters are selected in order to discuss these relevant plasma phenomena.

Ahedo, Eduardo

2011-12-01

91

Plasma Dictionary Website  

Microsoft Academic Search

In response to many inquiries for a list of plasma terms, a database driven Plasma Dictionary website (plasmadictionary.llnl.gov) was created that allows users to submit new terms, search for specific terms or browse alphabetic listings. The Plasma Dictionary website contents began with the Fusion & Plasma Glossary terms available at the Fusion Energy Educational website (fusedweb.llnl.gov). Plasma researchers are encouraged

Don Correll; Robert Heeter; Mitch Alvarez

2000-01-01

92

Plasma surface cleaning using microwave plasmas  

SciTech Connect

In a microwave electron cyclotron resonance (ECR) plasma source, reactive plasmas of oxygen and its mixture with argon are used for plasma-cleaning experiments. Aluminum test samples (0.95 {times} 1.9 cm) were coated with thin films ({le} 20 {mu}m in thickness) of Shell Vitrea oil and cleaned by using such reactive plasmas. The plasma cleaning was done in various discharge conditions with fixed microwave power, rf power, biased potential, gas pressures (0.5 and 5 mtorr), and operating time up to 35 min. The status of plasma cleaning has been monitored by using mass spectroscopy. Mass loss of the samples after plasma cleaning was measured to estimate cleaning rates. Measured clean rates of low pressure (0.5 mtorr) argon/oxygen plasmas were as high as 2.7 {mu}/min. X-ray photoelectron spectroscopy was used to determine cleanliness of the sample surfaces and confirm the effectiveness of plasma cleaning in achieving atomic levels of surface cleanliness. In this paper, significant results are reported and discussed.

Tsai, C.C.; Haselton, H.H.; Nelson, W.D.; Schechter, D.E. [Oak Ridge National Lab., TN (United States); Thompson, L.M.; Campbell, V.B.; Glover, A.L.; Googin, J.M. [Oak Ridge Y-12 Plant, TN (United States)

1993-11-01

93

Nonlinear plasma wave in magnetized plasmas  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

94

A Decade of Plasma Camp  

Microsoft Academic Search

To engage high school physics teachers in plasma physics, The Princeton Plasma Physics Laboratory (PPPL), established The Plasma Science and Fusion Energy Institute, or Plasma Camp, in 1998. Plasma camp is an intensive summer professional development workshop aimed at introducing teachers and their students to physics topics relevant to fusion plasma research and developing ways to integrate plasma physics into

Doreen Nuzzolese; Andrew Zwicker; Nicholas Guilbert; James Morgan

2008-01-01

95

Beams and Plasmas  

NASA Astrophysics Data System (ADS)

The long term goal of the Cooler Experiment-30 plasma trap is for its use as a target in the Indiana University Cyclotron Facility Storage Ring. Before it can be used as a target, the trap must be able to contain a stable and dense plasma. The implement ation of the current trap design facilitated the observation of several properties of electron plasmas in the trap. These properties include the number of electrons in the trap, radius of the plasma, temperature of the plasma, ionization of hydrogen in t he trap, and the charge density wave properties of the plasma.

Gerberich, Heather

1996-11-01

96

Study of Plasma Chemistry and Plasma Processing.  

National Technical Information Service (NTIS)

The final technical report describes studies related to plasma chemistry and plasma processing funded by the Office of Naval Research during the period December 15, 1979-June 15, 1983 (Contract : N00014-80-C-0244, NR SRO-016). Two experimental systems nee...

H. J. Oskam

1983-01-01

97

Plasma Column Generation Study.  

National Technical Information Service (NTIS)

A study has been conducted on methods of producing unconfined plasma columns of length one to twenty meters in air at atmospheric pressure. Turbulent combustion gas jet and flammable liquid jets were considered for producing the plasma columns, which were...

P. S. Masser W. Cramer R. E. Petersen A. J. Hoehn E. K. Parks

1969-01-01

98

Plasma photonic crystal  

Microsoft Academic Search

Plasma photonic crystals are presented in this paper. A plasma photonic crystal can control the propagation of electromagnetic\\u000a waves. Similar to other photonic crystals, the permittivity of a plasma photonic crystal is distributed as periodic arrays.\\u000a The properties of periodic arrays of plasma can broaden the range of frequency and enhance the efficiency of beam-wave interaction.\\u000a In special uses, the

Wei Li; Yong Zhao; Ruizhen Cui; Haitao Zhang

2009-01-01

99

Plasma momentum coupling  

Microsoft Academic Search

Momentum transfer between a high velocity aluminum plasma (2 x 10 to the 7th power cm\\/sec) and a stationary magnetized air plasma is experimentally investigated to determine if any collisionless processes are operating at high Alfven Mach number. The aluminum plasma expands within a cone (1\\/20 steradium) into the large volume of air plasma with the variable applied magnetic field

T. L. Cronburg; D. A. Reilly

1975-01-01

100

Basic plasma physics II  

Microsoft Academic Search

The basic physics of classical ideal plasmas is presented in reviews of recent theoretical and experimental investigations, with an emphasis on nonlinear interactions violating the assumptions of weak turbulence. Topics examined include Kolmogorov spectra, parametric instabilities in magnetoactive plasmas, collapse and self-focusing of Langmuir waves, collective dissipation and transport, spontaneous reconnection of magnetic-field lines in a collisionless plasma, collective-beam\\/plasma interaction,

A. A. Galeev; R. N. Sudan

1984-01-01

101

Arc Plasma Torch Modeling  

Microsoft Academic Search

Arc plasma torches are the primary components of various industrial thermal plasma processes involving plasma spraying, metal\\u000a cutting and welding, thermal plasma CVD, metal melting and remelting, waste treatment, and gas production. They are relatively\\u000a simple devices whose operation implies intricate thermal, chemical, electrical, and fluid dynamics phenomena. Modeling may\\u000a be used as a means to better understand the physical

J. P. Trelles; C. Chazelas; A. Vardelle; J. V. R. Heberlein

2009-01-01

102

Plasma diagnostics for FED  

SciTech Connect

An overview of the plasma diagnostic instruments recommended for the Fusion Engineering Device (FED) is described. First the role and need for plasma diagnostics is discussed. This is followed by an identification of particles and radiation eminating from the plasma. Next some design considerations are presented for the overall set of diagnostic instruments. Finally, instruments used for control and for plasma performance measurements are included in separate lists.

Nelson, W.D.

1981-01-01

103

Plasma in astrophysics  

SciTech Connect

Two examples of plasma phenomena of importance to astrophysics are reviewed. These are examples where astrophysical understanding hinges on further progress in plasma physics understanding. The two examples are magnetic reconnection and the collisionless interaction between a population of energetic particles and a cooler gas or plasma, in particular the interaction between galactic cosmic rays and the interstellar medium.

Kulsrud, R.M.

1982-10-01

104

Electronically steerable plasma mirror  

Microsoft Academic Search

Electronic steering of microwave beams using a plasma mirror allows the use of wide instantaneous bandwidth waveforms. Areas of application for a plasma mirror based antenna system include ship self-defense, high-resolution radar imaging, high data rate communications, spread spectrum links, and remote sensing. Recent experiments have demonstrated that a planar plasma mirror immersed in a magnetic field, can be formed

J. Mathew; R. A. Meger; J. A. Gregor; D. P. Murphy; R. E. Pechacek; R. F. Fernsler; W. M. Manheimer

1996-01-01

105

Antimatter plasmas and antihydrogen  

Microsoft Academic Search

Recent successes in confining antimatter in the form of positron and antiproton plasmas have created new scientific and technological opportunities. Plasma techniques have been the cornerstone of experimental work in this area, and this is likely to be true for the foreseeable future. Work by a number of groups on trapping antimatter plasmas is summarized, and an overview of the

R. G. Greaves; C. M. Surko

1997-01-01

106

Metastable supercooled plasma  

Microsoft Academic Search

The computer ab initio simulation and analytical theory that revealed unexpected nonergodic properties in a classical Coulomb plasma are reviewed. The results of a many-charged-particle system simulation predict the possible existence of a real metastable plasma, supercooled with respect to its degree of ionisation. The existence of such a plasma state is a consequence of the entropy conservation in isolated

S A Mayorov; Aleksei N Tkachev; Sergei I Yakovlenko

1994-01-01

107

Magnetohydrodynamics of Plasma Relaxation  

Microsoft Academic Search

This monograph on magnetohydrodynamic (MHD) relaxation in plasmas by Ortolani and Schnack occupies a fascinating niche in the plasma physics literature. It is rare in the complex and often technically sophisticated subject of plasma physics to be able to isolate a topic and deal with it comprehensively in a mere 180 pages. Furthermore, it brings a refreshingly original and personal

J. W. Connor

1998-01-01

108

Liquid and Solid Ion Plasmas.  

National Technical Information Service (NTIS)

Atomic ions which are stored in electromagnetic fields are an example o nonneutral plasmas. Laser techniques allow control of plasma angular momentum and provide plasma cooling to temperatures much less than 1K. Using imaging techniques, plasma spatial in...

D. J. Wineland J. J. Bollinger

1992-01-01

109

Modelling of thermal plasma systems  

Microsoft Academic Search

Thermal plasma systems, comprising two different states of matter, plasma and particles, for thermal plasma processing were studied. The primary objective of is to develop computational models for thermal plasma systems and to extent the knowledge of thermal plasma processing through theoretical considerations. The thermal plasma is regarded as a continuum fluid, and the global governing equations can be derived

Yau-Pin Chyou

1987-01-01

110

Model of detached plasmas  

SciTech Connect

Recently a tokamak plasma was observed in TFTR that was not limited by a limiter or a divertor. A model is proposed to explain this equilibrium, which is called a detached plasma. The model consists of (1) the core plasma where ohmic heating power is lost by anomalous heat conduction and (2) the shell plasma where the heat from the core plasma is radiated away by the atomic processes of impurity ions. A simple scaling law is proposed to test the validity of this model.

Yoshikawa, S.; Chance, M.

1986-07-01

111

Mirror plasma apparatus  

DOEpatents

A mirror plasma apparatus which utilizes shielding by arc discharge to form a blanket plasma and lithium walls to reduce neutron damage to the wall of the apparatus. An embodiment involves a rotating liquid lithium blanket for a tandem mirror plasma apparatus wherein the first wall of the central mirror cell is made of liquid lithium which is spun with angular velocity great enough to keep the liquid lithium against the first material wall, a blanket plasma preventing the lithium vapor from contaminating the plasma.

Moir, Ralph W. (Livermore, CA)

1981-01-01

112

Plasma-surface interactions  

NASA Astrophysics Data System (ADS)

Materials processing is at a crossroads. Currently much of industrially viable materials processing is via plasmas. However as this processing has reached the nano-scale, development of industrially viable processes has become more and more difficult. In part this is because of all of the free parameters that exist in plasmas. To overcome this economic issue, tool vendors and semiconductor companies have turned to complex computational models of processing plasmas. For those models to work, one requires a through understanding of all of the gas-phase and surface-phase processes that are exhibited in plasmas. Unfortunately, these processes are not well understood. In this paper we will examine a new model of plasma-surface processes. Specifically we will examine how the plasma-surface interactions set how process tools work. From this we will examine the potential future of the plasma-processing field.

Goeckner, Matthew

2009-04-01

113

Advanced plasma diagnostics for plasma processing  

NASA Astrophysics Data System (ADS)

A new, non-intrusive, non-perturbing diagnostic method was developed that can be broadly applied to low pressure, weakly ionized plasmas and glow discharges-trace rare gases optical emission spectroscopy (TRG-OES). The method is based on a comparison of intensities of atomic emission from trace amounts of inert gases (He, Ne, Ar, Kr, and Xe) that are added to the discharge to intensities calculated from the theoretical model. The model assumes a Maxwellian electron energy distribution function (EEDF), computes the population of emitting levels both from the ground state and the metastable states of rare gases, and from the best fit between theory and experiment determines electron temperature (Te). Subject to conditions, TRG-OES can also yield electron density or its upper or lower limit. From the comparison of the emission from levels excited predominantly by high energy electrons to that excited by low energy electrons, information about the EEDF can be obtained. The use of TRG-OES also allows a traditionally qualitative actinometry technique (determination of concentration of radical species in plasma through optical emission) to become a precise quantitative method by including Te and rare gases metastables effects. A combination of TRG-OES, advanced actinometry, and Langmuir probe measurements was applied to several different plasma reactors and regimes of operation. Te measurements and experiments to correct excitation cross section were conducted in a laboratory helical resonator. Two chamber configuration of a commercial (Lam Research) metal etcher were studied to determine the effects of plasma parameters on plasma-induced damage. Two different methods (RF inductive coupling and ultra-high frequency coupling) for generating a plasma in a prototype reactor were also studied. Pulsed plasmas, a potential candidate to eliminate the plasma-induced damage to microelectronics devices that occurs in manufacturing due to differential charging of the wafer, have been studied in a laboratory inductively- coupled reactor. Time dependencies of Te,ne,n+ i,n- i and the transition of the plasma from its electron-ion to ion-ion state (the ion- ion state promises to eliminate the plasma-induced damage) were investigated with a combination of the Langmuir probe, microwave interferometry, and TRG-OES.

Malyshev, Mikhail Victorovich

1999-10-01

114

Plasma-Sheath Revisited  

NASA Astrophysics Data System (ADS)

The formulation of the plasma-wall problem goes back to Langmuir and Tonks, but up to this day has remained an intriguing and controversial problem. Its numerical solution shows a smooth transition from plasma to sheath and provides a limited understanding of the plasma-sheath interface. In many applications (such as plasma probe diagnostics, dc and rf discharges) the electrical properties of bounded plasma-sheath systems are controlled by the sheath. It is therefore common to study plasma and sheath separately using different mathematical models which provide an insight into each region. These models are quite simple, and often can be solved analytically, or by using simple numerical schemes. When plasma and sheath are studied separately, one has to decide how to join the solutions of the corresponding models. Two approaches are found in the literature to deal with this problem: one is the method of matched asymptotic expansions and the second one is patching. Application of asymptotic matching techniques to the plasma-wall problem has led to important theoretical results. However, the mathematical formalism and complexity associated with that method makes it difficult to use in applications. Moreover, the asymptotic plasma and the sheath solutions cannot be matched directly, and the modeling of an intermediate layer between the plasma and the sheath is required for a successful matching. Patching seems to be a more practical approach. Its idea is to join solutions of two different models by forcing their values and perhaps several derivatives to agree at some chosen point (the patching point). The main purpose of patching is to obtain continuity, but, in theory, smoothness is also possible. In contrast to asymptotic matching, it is possible to patch the plasma and the sheath solutions directly, eliminating the need for modeling an intermediate layer. The subject of this presentation is to discuss various fluid plasma and sheath models and their relationship to the corresponding plasma-wall problem. We will discuss the regions where the plasma and the sheath solutions are valid and develop discrete two-media plasma-sheath models which can be used to express the sheath characteristics through the plasma characteristics, or to find the integral characteristics of the sheath for given plasma parameters.

Sternberg, Natalia

2012-10-01

115

What is a plasma?  

SciTech Connect

This introduction will define the plasma fourth state of matter, where we find plasmas on earth and beyond, and why they are useful. There are applications to many consumer items, fusion energy, scientific devices, satellite communications, semiconductor processing, spacecraft propulsion, and more. Since 99% of our observable universe is ionized gas, plasma physics determines many important features of astrophysics, space physics, and magnetosphere physics in our solar system. We describe some plasma characteristics, examples in nature, some useful applications, how to create plasmas. A brief introduction to the theoretical framework includes the connection between kinetic and fluid descriptions, quasi neutrality, Debye shielding, ambipolar electric fields, some plasma waves. Hands-on demonstrations follow. More complete explanations will follow next week.

Intrator, Thomas P. [Los Alamos National Laboratory

2012-08-30

116

Limits to plasma science  

SciTech Connect

Since fundamental limits to plasma science are the well-known ones of relativity and quantum mechanics, various practical limits are discussed for plasma science in several domains of current interest: applications (mainly controlled thermonuclear fusion, both magnetic confinement and ablative compression) investigation of natural plasma (in space near earth and solar system and in astrophysics). Some historical flavor is imparted by also considering the effect of limits on three domains of interest since the 1945: plasma frequency devices for microwave applications at millimeter wavelengths, solid-state plasmas, and reentry vehicle plasmas. In general, while one can identify the nature of the limits, refining their 'values' or making firm predictions in view of possible 'breakthroughs' is seen to be unlikely to be worth doing.

Johnston, T.W.

1981-01-01

117

23rd National Symposium on Plasma Science & Technology (PLASMA2008)  

Microsoft Academic Search

It is our pleasure to present the proceedings of the 23rd National Symposium on Plasma Science and Technology (PLASMA-2008) held at Bhabha Atomic Research Center, Mumbai, 10– December 2008 in association with the Plasma Science Society of India. The Plasma Science Society of India has been holding regular symposia on general topics related to Plasma. The symposium was designed to

V K Mago; P V Ananthapadmanabhan; D S Patil; A K Das

2010-01-01

118

Plasma androgens in autism  

Microsoft Academic Search

Plasma levels of testosterone and the adrenal androgen dehydroepiandrosterone sulfate (DHEA-S) were measured in male autistic subjects (31 prepubertal, 8 postpubertal), mentally retarded\\/cognitively impaired subjects (MR, 12 prepubertal), and normal control subjects (NC, 10 prepubertal, 11 postpubertal). Mean levels of plasma testosterone were similar in the postpubertal autistic (4.54+1.12 ng\\/ml) and postpubertal NC (5.02±1.87 ng\\/ml) groups. Plasma DHEA-S levels in

Sylvie Tordjman; George M. Anderson; P. Anne McBride; Margaret E. Hertzig; Margaret E. Snow; Laura M. Hall; Pierre Ferrari; Donald J. Cohen

1995-01-01

119

Plasma Adiabatic Lapse Rate  

NASA Astrophysics Data System (ADS)

The plasma analog of an adiabatic lapse rate (or temperature variation with height) in atmospheric physics is obtained. A new source of plasma temperature gradient in a binary ion species mixture is found that is proportional to the concentration gradient ??? and difference in average ionization states Z2-Z1. Application to inertial-confinement-fusion implosions indicates a potentially strong effect in plastic (CH) ablators that is not modeled with mainline (single-fluid) simulations. An associated plasma thermodiffusion coefficient is derived, and charge-state diffusion in a single-species plasma is also predicted.

Amendt, Peter; Bellei, Claudio; Wilks, Scott

2012-08-01

120

Plasma adiabatic lapse rate.  

PubMed

The plasma analog of an adiabatic lapse rate (or temperature variation with height) in atmospheric physics is obtained. A new source of plasma temperature gradient in a binary ion species mixture is found that is proportional to the concentration gradient ?? and difference in average ionization states Z(2)-Z(1). Application to inertial-confinement-fusion implosions indicates a potentially strong effect in plastic (CH) ablators that is not modeled with mainline (single-fluid) simulations. An associated plasma thermodiffusion coefficient is derived, and charge-state diffusion in a single-species plasma is also predicted. PMID:23006377

Amendt, Peter; Bellei, Claudio; Wilks, Scott

2012-08-16

121

Princeton Plasma Physics Laboratory  

SciTech Connect

This report discusses the following topics: principal parameters achieved in experimental devices fiscal year 1990; tokamak fusion test reactor; compact ignition tokamak; Princeton beta experiment- modification; current drive experiment-upgrade; international collaboration; x-ray laser studies; spacecraft glow experiment; plasma processing: deposition and etching of thin films; theoretical studies; tokamak modeling; international thermonuclear experimental reactor; engineering department; project planning and safety office; quality assurance and reliability; technology transfer; administrative operations; PPPL patent invention disclosures for fiscal year 1990; graduate education; plasma physics; graduate education: plasma science and technology; science education program; and Princeton Plasma Physics Laboratory reports fiscal year 1990.

Not Available

1990-01-01

122

Plasma Processing Of Hydrocarbon  

SciTech Connect

The Idaho National Laboratory (INL) developed several patented plasma technologies for hydrocarbon processing. The INL patents include nonthermal and thermal plasma technologies for direct natural gas to liquid conversion, upgrading low value heavy oil to synthetic light crude, and to convert refinery bottom heavy streams directly to transportation fuel products. Proof of concepts has been demonstrated with bench scale plasma processes and systems to convert heavy and light hydrocarbons to higher market value products. This paper provides an overview of three selected INL patented plasma technologies for hydrocarbon conversion or upgrade.

Grandy, Jon D; Peter C. Kong; Brent A. Detering; Larry D. Zuck

2007-05-01

123

MICROFABRICATED PROBES FOR LABORATORY PLASMAS  

Microsoft Academic Search

We present the first of a series of microfabricated sensors for directly measuring fundamental plasma parameters with unprecedented resolution in typical laboratory plasmas. Microfabricated probes hold the promise of significantly advancing basic plasmas physics by enabling the measurement of some fundamental plasma processes under controlled conditions at the relatively high plasma densities typically of interest. Our first probes are arrays

Janet A. Stillman; Franklin C. Chiang; Patrick A. Pribyl; Mio Nakamoto; Walter Gekelman; Jack W. Judy

124

Laboratory Dipole Plasma Physics  

NASA Astrophysics Data System (ADS)

Modern laboratory studies of plasma confined by a strong dipole magnet originated twenty years ago when it was learned that planetary magnetospheres have centrally-peaked plasma pressure profiles that form naturally when solar wind drives plasma circulation and heating. Unlike other internal rings devices, like spherators and octupoles, the magnetic flux tubes of the dipole field expand rapidly with radius. Unlike plasma confinement devices that obtain stability from magnetic shear and average good curvature, like tokamaks and levitrons, the dipole-confined plasma obtains stability from plasma compressibility. These two geometric characteristics of the dipole field have profound consequences: (i) plasma can be stable with local beta exceeding unity, (ii) fluctuations can drive either heat or particles inward to create stationary profiles that are strongly peaked, and (iii) the confinement of particles and energy can decouple. During the past decade, several laboratory dipole experiments and modeling efforts have lead to new understanding of interchange, centrifugal and entropy modes, nonlinear gyrokinetics, and plasma transport. Two devices, the LDX experiment at MIT and RT-1 at the University of Tokyo, operate with levitated superconducting dipole magnets. With a levitated dipole, not only is very high-beta plasma confined in steady state but, also, levitation produces high-temperature at low input power and demonstrates that toroidal magnetic confinement of plasma does not require a toroidal field. Modeling has explained many of the processes operative in these experiments, including the observation of a strong inward particle pinch. Turbulent low-frequency fluctuations in dipole confined plasma cause adiabatic transport and form a fundamental linkage between the radial variation of flux-tube volume and the centrally peaked density and pressure profiles.

Kesner, Jay

2011-11-01

125

Triggered plasma opening switch  

Microsoft Academic Search

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open

Mendel

1986-01-01

126

Triggered plasma opening switch  

Microsoft Academic Search

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open

Mendel; Clifford W

1988-01-01

127

Plasma treatment of polydimethylsiloxane  

Microsoft Academic Search

Plasma treatment of silicone surfaces is a useful way of increasing wettability to improve adhesion and a first step in producing various organosilicon thin-film composites. Despite numerous earlier studies, there is no consensus on the effect of plasma treatment nor on the mechanism of the subsequent hydrophobic recovery. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to

Michael J. Owen; Patrick J. Smith

1994-01-01

128

Plasma Dust Crystallization.  

National Technical Information Service (NTIS)

In a ground-based definition study, a concept for a new type of microgravity experiment is developed. We formed a new state of matter: a crystalline lattice structure of charged micron-size spheres, suspended in a charge-neutral plasma. The plasma is form...

J. Goree H. Thomas G. Morfill

1994-01-01

129

Plasma Generated Spherules  

Microsoft Academic Search

Z-pinch plasma simulations have been performed that indicate the production of spherules under certain experimental parameters. (A. L. Peratt, private communication) While performing experiments dealing with the impact of plasma discharges on various materials, we observed that spherules were created at the surface of some of the materials. For specific materials and conditions, spherules were always produced. Both individual spherules

C. J. Ransom

2005-01-01

130

Plasma diagnostic reflectometry  

Microsoft Academic Search

Theoretical and experimental studies of plasma diagnostic reflectometry have been undertaken as a collaborative research project between the Lawrence Livermore National Laboratory (LLNL) and the University of California Department of Applied Science Plasma Diagnostics Group under the auspices of the Laboratory Directed Research and Development Program at LLNL. Theoretical analyses have explored the basic principles of reflectometry to understand its

B. I. Cohen; B. B. Afeyan; J. C. Garrison; T. B. Kaiser; N. C. Jr. Luhmann; C. W. Domier; A. E. Chou; S. Baang

1996-01-01

131

Steam plasma arc cutting  

Microsoft Academic Search

Summary form only given. Plasma arc cutting is a widely used method for cutting metals. The availability of small portable units using compressed air as plasma gas makes these devices suitable for use in workshops. However, the need for compressed air means less flexibility in field applications. Possible solution strategies to overcome this disadvantage are the integration of the air

H. Pauser; J. Laimer; H. Stori

1999-01-01

132

Plasma engineering for MARS  

SciTech Connect

The two-year Mirror Advanced Reactor Study (MARS) has resulted in the conceptual design of a commercial, electricity-producing fusion reactor based on tandem mirror confinement. The physics basis for the MARS reactor was developed through work in two highly coupled areas of plasma engineering: magnetics and plasma performance.

Carlson, G.A.; Baldwin, D.E.; Barr, W.L.

1983-03-24

133

Plasma Assisted Combustion Technologies  

Microsoft Academic Search

This paper provides an overview, classification, and analyzes of the most advanced plasma based technologies developed mainly to improve ignition reliability, avoid flame instabilities, reduce emissions in a wide variety of applications, including aerospace propulsion systems, land based power generation units, technological boilers, furnaces, incinerators, heaters, dryers, etc. The fuel reformation, coal gasification, and waste-into-energy plasma processing technologies have been

S. Matveeva; E. Kirchuk

2009-01-01

134

Aerospatiale Industrial Thermal Plasmas.  

National Technical Information Service (NTIS)

Work carried out on nontransferred plasma torches of 2, 4, and 0.8 MW to be used in metallurgic, iron making, casting foundry, and environment industrial plants is described. The plants operation, the plasma system behavior, and the main process' results ...

M. Labrot

1991-01-01

135

Ultracold Neutral Plasmas.  

National Technical Information Service (NTIS)

By photoionizing a sample of laser-cooled xenon atoms, we create ultracold neutral plasmas with initial temperatures of 1-1000 K and densities as high as l0(exp10)/cu cm. The plasma is formed by the trapping of electrons by the residual positive charge th...

M. J. Lim S. Kulin S. L. Rolston T. C. Killian

2002-01-01

136

Plasma sheet boundary layer  

Microsoft Academic Search

The plasma sheet boundary layer is a temporally variable transition region located between the magnetotail lobes and the central plasma sheet. We have made a survey of these regions by using particle spectra and three-dimensional velocity-space distributions sampled by the ISEE 1 LEPEDEA. Ion composition measurements obtained by the Lockhead ion mass spectrometers indicate that ionospheric ions play a crucial

T. E. Eastman; L. A. Frank; W.K. Peterson; W. Lennartsson

1984-01-01

137

Nonequilibrium lighting plasmas  

Microsoft Academic Search

The science of a variety of devices employing nonequilibrium lightning plasmas is reviewed. The devices include the fluorescent lamp, the low-pressure sodium lamp, the neon sign, ultraviolet lamps, glow indicators, and a variety of devices used by spectroscopists, such as the hollow cathode light source. The plasma conditions in representative commercial devices are described. Recent research on the electron gas,

J. T. Dakin

1991-01-01

138

Plasma-Grid Interaction  

Microsoft Academic Search

Plasma interaction with a grid is important in a number of applications. In neutral beam etching, for example, a grid is used to neutralize ions and generate collimated beams of energetic neutrals for anisotropic etch without charge damage. Also, many ion sources and satellite thrusters are based on extraction of an ion beam from a plasma through a grid. The

Chang-Koo Kim; Demetre Economou; Justine Johannes; Timothy Bartel

1999-01-01

139

Atoms in dense plasmas  

SciTech Connect

Recent experiments with high-power pulsed lasers have strongly encouraged the development of improved theoretical understanding of highly charged ions in a dense plasma environment. This work examines the theory of dense plasmas with emphasis on general rules which govern matter at extreme high temperature and density. 106 refs., 23 figs.

More, R.M.

1986-01-01

140

Plasma Sterilization Experiments.  

National Technical Information Service (NTIS)

The purpose of this project was to investigate the feasibility of antibacterial plasma treatment of biological tissue. A low- temperature plasma was produced in air that killed 1E5-1E6 bacterial populations on synthetic skin in under 20 seconds. The bacte...

D. Blessing M. Moore R. Moore

2008-01-01

141

Triggered plasma opening switch  

DOEpatents

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open the switch.

Mendel, Clifford W. (Albuquerque, NM)

1988-01-01

142

80 Years of Plasma  

Microsoft Academic Search

Irving Langmuir proposed the term 'plasma' in a paper in 1928 (Proc. Natl Acad. Sci. USA14 627–637) to describe a 'region containing balanced charges of ions and electrons'. There does not appear to be any record of the thinking behind this proposal, so it is difficult to be definitive. One idea is that since the Greek word 'plasma' was used

2009-01-01

143

SUPERFAST THERMALIZATION OF PLASMA  

DOEpatents

A method is given for the superfast thermalization of plasma by shock conversion of the kinetic energy stored in rotating plasma rings or plasmoids colliding at near supersonic speeds in a containment field to heat energy in the resultant confined plasma mass. The method includes means for generating rotating plasmoids at the opposite ends of a Pyrotron or Astron containment field. The plasmoids are magnetically accelerated towards each other into the opposite ends of time containment field. During acceleration of the plasmoids toward the center of the containment field, the intensity of the field is sequentially increased to adiabatically compress the plasmoids and increase the plasma energy. The plasmoids hence collide with a violent shock at the eenter of the containment field, causing the substantial kinetic energy stored in the plasmoids to be converted to heat in the resultant plasma mass. (AEC)

Chang, C.C.

1962-06-12

144

SHEET PLASMA DEVICE  

DOEpatents

An ion-electron plasma heating apparatus of the pinch tube class was developed wherein a plasma is formed by an intense arc discharge through a gas and is radially constricted by the magnetic field of the discharge. To avoid kink and interchange instabilities which can disrupt a conventional arc shortiy after it is formed, the apparatus is a pinch tube with a flat configuration for forming a sheet of plasma between two conductive plates disposed parallel and adjacent to the plasma sheet. Kink instabilities are suppressed by image currents induced in the conductive plates while the interchange instabilities are neutrally stable because of the flat plasma configuration wherein such instabilities may occur but do not dynamically increase in amplitude. (AEC)

Henderson, O.A.

1962-07-17

145

Plasma Physics Research and Instrumentation.  

National Technical Information Service (NTIS)

Experiments in plasma research, technology and applied plasma physics, and plasma theory and computation are reported. The following research activities are identified as being of special interest: Several toroidal confinement devices were constructed. On...

1971-01-01

146

Running a reproducible plasma process  

SciTech Connect

Although plasma processing has become an indispensable part of modern integrated circuit fabrication, and modern plasma processing equipment has become sophisticated, it is still not a simple matter to run a reproducible plasma process.

Chapman, B.; Gray, D.E. (Lucas Laboratories, San Jose, CA 95131 (USA))

1990-02-05

147

Plasma sheath criterion in thermal electronegative plasmas  

SciTech Connect

The sheath formation criterion in electronegative plasma is examined. By using a multifluid model, it is shown that in a collisional sheath there will be upper as well as lower limits for the sheath velocity criterion. However, the parameters of the negative ions only affect the lower limit.

Ghomi, Hamid [Laser and Plasma Research Institute, Shahid Beheshti University, Evin 1983963113, Tehran (Iran, Islamic Republic of); Khoramabadi, Mansour; Ghorannevis, Mahmod [Plasma Physics Research Center, Science and Research Campus of Islamic Azad University, P.O. Box 14665-678, Tehran (Iran, Islamic Republic of); Shukla, Padma Kant [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2010-09-15

148

Novel Inductively Coupled Plasma Source  

Microsoft Academic Search

Plasma Research Laboratory, Dublin City University Novel Inductively Coupled Plasma Source A novel high-pressure, high-power-density-compatible plasma source is investigated. Possible applications include high brightness lightning, effluent abatement and chemical activation for downstream use. The systems comprises an inductively coupled rf antenna and plasma. The plasma housing chamber and plasma act as a secondary windings to the antenna. The design features

Andrew Rybin; Albert R. Ellingboe

2002-01-01

149

Plasma electrolysis for surface engineering  

Microsoft Academic Search

This paper overviews the relatively new surface engineering discipline of plasma electrolysis, the main derivative of this being plasma electrolytic deposition (PED), which includes techniques such as plasma electrolytic oxidation (PEO) and plasma electrolytic saturation (PES) processes such as plasma electrolytic nitriding\\/carburizing (PEN\\/PEC). In PED technology, spark or arc plasma micro-discharges in an aqueous solution are utilised to ionise gaseous

A. L. Yerokhin; X. Nie; A. Leyland; A. Matthews; S. J. Dowey

1999-01-01

150

Dense Hypervelocity Plasma Jets  

NASA Astrophysics Data System (ADS)

We are developing high velocity dense plasma jets for fusion and HEDP applications. Traditional coaxial plasma accelerators suffer from the blow-by instability which limits the mass accelerated to high velocity. In the current design blow-by is delayed by a combination of electrode shaping and use of a tailored plasma armature created by injection of a high density plasma at a few eV generated by arrays of capillary discharges or sparkgaps. Experimental data will be presented for a complete 32 injector gun system built for driving rotation in the Maryland MCX experiment, including data on penetration of the plasma jet through a magnetic field. We present spectroscopic measurements of plasma velocity, temperature, and density, as well as total momentum measured using a ballistic pendulum. Measurements are in agreement with each other and with time of flight data from photodiodes and a multichannel PMT. Plasma density is above 10^15 cm-3, velocities range up to about 100 km/s. Preliminary results from a quadrature heterodyne HeNe interferometer are consistent with these results.

Case, Andrew; Witherspoon, F. Douglas; Messer, Sarah; Bomgardner, Richard; Phillips, Michael; van Doren, David; Elton, Raymond; Uzun-Kaymak, Ilker

2007-11-01

151

Prototype Plasma Dynamo Experiments  

NASA Astrophysics Data System (ADS)

The Madison Plasma Dynamo Experiment (MPDX) is under construction to explore the self-excitation processes of a range of astrophysical dynamos. NIMROD simulations of von K'arm'an flow, in which the upper and lower hemispheres of the plasma are spun in opposite directions, have shown that the resulting two vortex flow can produce a dynamo when the magnetic Reynolds number is sufficiently high. This poster discusses prototype experiments on the Plasma Couette Experiment (PCX) to create von K'arm'an flow. The PCX (like the MPDX) uses an axisymmetric multicusp plasma confinement scheme that works in tandem with electrodes of alternating bias to create flow at the plasma boundary via ExB drift. This poster will review the theory with an emphasis on requirements on the plasma parameters and then show that the measured plasma parameters (ne 10^17 m-3, Te˜ 10 eV) and flow speeds of 10 km/sec are high enough to self-excite, but are in a regime in which Hall MHD will likely be important. Higher densities (possible with higher power LaB6 cathodes) will be required to operate in the MHD regime. Work supported by NSF.

Weisberg, David; Forest, Cary; Collins, Cami; Katz, Noam; Khalzov, Ivan; Wallace, John; Clark, Mike

2010-11-01

152

Origins of magnetospheric plasma  

SciTech Connect

A review is given of recent (1987-1990) progress in understanding of the origins of plasmas in the earth's magnetosphere. In counterpoint to the early supposition that geomagnetic phenomena are produced by energetic plasmas of solar origin, 1987 saw the publication of a provocative argument that accelerated ionospheric plasma could supply all magnetospheric auroral and ring current particles. Significant new developments of existing data sets, as well as the establishment of entirely new data sets, have improved the ability to identify plasma source regions and to track plasma through the magnetospheric system of boundary layers and reservoirs. These developments suggest that the boundary between ionospheric and solar plasmas, once taken to lie at the plasmapause, actually lies much nearer to the magnetopause. Defining this boundary as the surface where solar wind and ionosphere contribute equally to the plasma, it is referred to herein as the 'geopause'. It is now well established that the infusion of ionospheric O(+) plays a major role in the storm-time distention of the magnetotail and inflation of the inner magnetosphere. After more than two decades of observation and debate, the question remains whether magnetosheric are protons of solar or terrestrial origin. 161 refs.

Moore, T.E. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

153

Plasma physics. Proceedings. 7th Latin American Workshop on Plasma Physics (VII LAWPP 97), Caracas (Venezuela), 20 - 31 Jan 1997.  

NASA Astrophysics Data System (ADS)

The following topics were dealt with: general plasma theory, plasma confinement, shock waves and instabilities in plasma, plasma spectroscopy, astrophysical and space plasmas, pulse power experiments, plasma processing.

Martín, P.; Puerta, J.

154

Stirring Unmagnetized Plasma  

NASA Astrophysics Data System (ADS)

A new concept for spinning unmagnetized plasma is demonstrated experimentally. Plasma is confined by an axisymmetric multicusp magnetic field and biased cathodes are used to drive currents and impart a torque in the magnetized edge. Measurements show that flow viscously couples momentum from the magnetized edge (where the plasma viscosity is small) into the unmagnetized core (where the viscosity is large) and that the core rotates as a solid body. To be effective, collisional viscosity must overcome the ion-neutral drag due to charge-exchange collisions.

Collins, C.; Katz, N.; Wallace, J.; Jara-Almonte, J.; Reese, I.; Zweibel, E.; Forest, C. B.

2012-03-01

155

Plasma control and utilization  

DOEpatents

A plasma is confined and heated by a microwave field resonant in a cavity excited in a combination of the TE and TM modes while responding to the resonant frequency of the cavity as the plasma dimensions change to maintain operation at resonance. The microwave field is elliptically or circularly polarized as to prevent the electromagnetic confining field from going to zero. A high Q chamber having superconductive walls is employed to minimize wall losses while providing for extraction of thermonuclear energy produced by fusion of nuclei in the plasma.

Ensley, Donald L. (Danville, CA)

1976-12-28

156

Ultracold neutral plasmas  

SciTech Connect

Plasmas are collections of charged particles that can exhibit an impressively diverse set of collective phenomena. They exist in an extraordinary variety of environments and span a great range of densities and temperatures, from 15 million kelvin in the core of the Sun to 200 K in the ionosphere and from 10{sup 30} particles per cubic centimeter in a white dwarf to 1 particle per cm{sup 3} in interstellar space. They can find application in lighting sources, manufacturing of computer chips, and fusion energy research. Plasmas created in the laboratory are used to replicate and study those that occur naturally and to probe the fundamental and complex behavior of plasmas.

Killian, Thomas C.; Rolston, Steven L. [Rice University, Houston, Texas (United States); University of Maryland, College Park (United States)

2010-03-15

157

Thin plasmas - Galactic sources  

NASA Astrophysics Data System (ADS)

Various contributions to the study of X-ray and UV emissions from optically thin plasmas (OTP) are reviewed. The emissions are typical of the sun, stellar coronas, SNR, and hot interstellar media. Attention is given to analytical models of OTP emission, spectroscopic techniques for plasma diagnostics, wave modes, and instabilities in plasmas and solar coronal loop models. Consideration is also devoted to observational data on type II supernovas, data on the 3 K background at X-ray and UV wavelengths, and the relation between supernova occurrence and the density wave theory of spiral galaxy formation.

Pallavicini, R.

158

Laser beam-plasma coupling in laser solenoid plasmas  

Microsoft Academic Search

A model has been constructed to analyze the gross beam-plasma interaction in a laser solenoid plasma. The model includes a simple solution for a slab plasma response to a given laser beam, and a solution for axial beam-size variations in response to arbitrary axial plasma structure. The two solutions are combined to determine the coupled behavior. Trapping of the focused

L. C. Steinhauer

1976-01-01

159

Laser beam-plasma coupling in laser solenoid plasmas  

Microsoft Academic Search

A model has been constructed to analyze the gross beam-plasma interaction in a laser solenoid plasma. The model includes a simple solution for a slab plasma response to a given laser beam, and a solution for axial beam size variations in response to arbitrary axial plasma structure. The two solutions are combined to determine the coupled behavior. Trapping of the

Loren C. Steinhauer

1976-01-01

160

Impulsive Plasma Produced by a Coaxial Plasma Gun  

Microsoft Academic Search

This paper is concerned with an impulsive plasma mass produced by a coaxial plasma gun. According to spectroscopic observation the following results have been obtained. When the plasma is produced with an oscillatory current, the gun ejects more than two plasma masses successively. Except the first one they consist mainly of impurities. Spectral lines from helium are recognized only in

Katsumi Hirano; Juichi Irisawa; Yoshiei Nakano

1969-01-01

161

BOOK REVIEW: Kinetic theory of plasma waves, homogeneous plasmas  

Microsoft Academic Search

The linear theory of plasma waves in homogeneous plasma is arguably the most mature and best understood branch of plasma physics. Given the recently revised version of Stix's excellent Waves in Plasmas (1992), one might ask whether another book on this subject is necessary only a few years later. The answer lies in the scope of this volume; it is

M. Brambilla

1998-01-01

162

Arc plasma jets of a nontransferred plasma torch  

SciTech Connect

The dc plasma torches have been widely used as clean plasma sources for plasma processings such as plasma spraying and synthesis. The plasma flow of a nontransferred plasma torch used for thermal plasma processings is produced by the arc-gas interactions between a cathode tip and an anode nozzle and expands as a jet through the nozzle. In this work, numerically calculated images of the arc plasma characteristics are found over the entire plasma region, including both an arc-gas interacting region inside the torch and a jet expanding region outside the torch. A numerical model used assumes a local thermodynamic equilibrium (LTE) with near-electrode phenomena and compressible flow effects. The computational system is described by a two-dimensional (2-D) axisymmetric model which is solved for plasma temperature and velocity by a control volume approach with the modified SIMPLER algorithm in a real torch geometry.

Kang, K.D.; Hong, S.H. [Seoul National Univ. (Korea, Republic of). Dept. of Nuclear Engineering

1996-02-01

163

Multiple harmonic plasma emission  

SciTech Connect

A generalized weak turbulence theory for electromagnetic emission at multiple harmonics of the plasma frequency is developed. In the literature, the electromagnetic emission at the plasma frequency and/or its second harmonic has been intensively studied. However, the emission at harmonics higher than the second harmonic is scarcely discussed. In the present paper, the higher harmonic plasma emission is explained by taking the interactions between the transverse mode and electrostatic nonlinear eigenmodes into consideration. The present analysis incorporates electrostatic nonlinear harmonic Langmuir waves into the fully electromagnetic weak turbulence formalism recently reformulated on the basis of the statistical mechanical Klimontovich approach. The wave kinetic equations for the transverse electromagnetic and Langmuir waves interacting with the harmonic Langmuir waves are derived, on the basis of which the emission of electromagnetic waves near multiple harmonics of the plasma frequency is qualitatively discussed.

Yi, Sumin; Yoon, Peter H.; Ryu, Chang-Mo [Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Department of Physics, Pohang University of Science and Technology, Pohang (Korea, Republic of)

2007-01-15

164

Triggered Plasma Opening Switch.  

National Technical Information Service (NTIS)

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductor...

C. W. Mendel

1986-01-01

165

Gingival plasma cell granuloma  

PubMed Central

Plasma cell granuloma, also known as inflammatory pseudotumor is a tumor-like lesion that manifests primarily in the lungs. But it may occur in various other anatomic locations like orbit, head and neck, liver and rarely in the oral cavity. We here report an exceedingly rare case of gingival plasma cell granuloma in a 58 year old woman who presented with upper gingival polypoidal growth. The histopathological examination revealed a mass composed of proliferation of benign spindle mesenchymal cells in a loose myxoid and fibrocollagenous stroma along with dense infiltrate of chronic inflammatory cells predominantly containing plasma cells. Immunohistochemistry for kappa and lambda light chains showed a polyclonal staining pattern confirming a diagnosis of plasma cell granuloma.

Pandav, Amitkumar B; Gosavi, Alka V; Lanjewar, Dhaneshwar N; Jagadale, Rakhi V

2012-01-01

166

[Infection and plasma procalcitonin].  

PubMed

Procalcitonin, a propeptide of calcitonin, is normally produced in the C-cells of the thyroid gland, but it's plasma level markedly increases, mostly due to extra-thyroidal production in cases of severe infections (bacterial, parasitic and fungal) with systemic manifestations, especially in the presence of septic shock. Since noninfectious inflammatory reaction, viral infection and localized bacterial infections manifest only small to modest increases of procalcitonin in plasma, procalcitonin levels may be useful in differentiating between these diseases and sepsis. In addition, it has been suggested that procalcitonin is an early and good marker of elevated cytokines in patients with sepsis, and that it's plasma level is correlated with Sepsis-related Organ Failure Assessment (SOFA) score. Since plasma procalcitonin is measured easily, quickly and accurately by immunoluminometric assay, it is useful for early diagnosis of sepsis in patients with severe systemic inflammatory response syndrome and as an indicator of severity of sepsis in such patients. PMID:15741695

Yukioka, Hidekazu

2005-03-01

167

Plasma Erosion Opening Switch.  

National Technical Information Service (NTIS)

The Plasma Erosion Opening Switch (PEOS) can conduct high current (approx. MA), open quickly (<10ns), and withstand high voltage (approx. MV). This switching technique has been used in inductive energy storage experiments and can be used with existing gen...

R. J. Commisso G. Cooperstein R. A. Meger J. M. Neri P. F. Ottinger

1985-01-01

168

Electric Probes in Plasmas.  

National Technical Information Service (NTIS)

This paper provides a background for the use of Langmuir and gridded energy analyzer probes in diagnosing plasmas with varied characteristics. Theory is illustrated which governs the analysis of data from, and the design of these probes. Several probe ana...

B. Lipschultz I. Hutchinson B. LaBombard A. Wan

1985-01-01

169

Relativistic Plasma Dispersion Relation.  

National Technical Information Service (NTIS)

The relativistic plasma dispersion relation for waves propagating perpendicular to a constant magnetic field is transformed into a rapidly converging series of integrals. Landau damping of the electrostatic waves is recovered in the limit of zero magnetic...

B. N. A. Lamborn

1969-01-01

170

Relativistic plasma dispersion relation  

Microsoft Academic Search

The relativistic plasma dispersion relation for waves propagating perpendicular to a constant magnetic field is transformed into a rapidly converging series of integrals. Landau damping of the electrostatic waves is recovered in the limit of zero magnetic field.

B N A Lamborn; B. N. A

1969-01-01

171

Plasma Stabilization by Feedback  

NASA Astrophysics Data System (ADS)

A simple model is discussed which illustrates the general features of plasma stabilization by an external feedback system. This indicates that different phase relations in the feedback loop are needed to stabilize differing classes of electrostatic instability.

Taylor, J. B.; Lashmore-Davies, C. N.

1970-06-01

172

Lassa Fever Immune Plasma.  

National Technical Information Service (NTIS)

Lassa fever immune plasma is being obtained in Liberia, West Africa for the U.S. Army Medical Institute of Infectious Diseases by Columbia University associated with the Liberian Institute for Biomedical Research (LIBR). Additionally, epidemiological inve...

J. D. Frame

1979-01-01

173

PHOTOIONIZATIONAL PLASMAS. I. THEORY  

SciTech Connect

In this paper, an attempt is made to define the subject of photoionizational plasmas through rigorous mathematical formalism. The central results of this paper are the following. (1) A set of recursive equations is introduced for the computation of the charge state distributions in photoionizational plasmas. (2) Quantitative validity limits are given for both the collisional and the photoionizational domains. (3) A parameter that determines the charge state distribution in the photoionizational regime is introduced. (4) We provide detailed discussion about the most important components of the emission spectrum in the different equilibrium domains of the emitting plasma. Some of these components have not been reported so far as included in the analysis of such plasmas.

Salzmann, David; Wang Feilu; Zhao Gang [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Takabe, Hideaki, E-mail: David.Salzmann@weizmann.ac.il [Institute for Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan)

2011-11-20

174

Magnetospheric Plasma Physics  

NASA Astrophysics Data System (ADS)

Magnetospheric Plasma Physics is volume 4 of an ongoing series of review books entitled Developments in Earth and Planetary Sciences organized by the Center for Academic Publications Japan. The series is intended to stress Japanese work; however, the present volume was written by seven internationally selected authors who have reviewed works from a broad range of sources. This volume is composed of articles drawn from five lecture series presented at the Autumn College o f Plasma Physics, International Center for Theoretical Physics, Trieste, Italy, October-November 1979. The audiences for these lecture series were plasma and/or space plasma physicists, or students of the same, and the level and tone of this volume clearly reflect that condition.

Mauk, Barry H.

175

Transverse Plasma Wave Echos.  

National Technical Information Service (NTIS)

Transverse plasma echos can arise from two spatially separated, steady-state excitations, a transverse one at frequency omega 1 and a longitudinal one at frequency omega 2. Our theoretical results for the location, polarization, and other characteristics ...

B. D. Fried C. Olson

1968-01-01

176

Inductive Plasma Accelerator Development.  

National Technical Information Service (NTIS)

The work described in the report comprises: (a) Theoretical studies of the performance of an electromagnetic induction plasma accelerator for radiation-cooled applications, and for pulsed operation. (b) The improvement of pre-existing instrumentation for ...

G. Fonda-Bonardi R. Rosen

1968-01-01

177

Cold plasma dispersion surfaces  

Microsoft Academic Search

Following the work of Stringer (1963), this study presents three-dimensional plots of dispersion in a cold anisotropic plasma. The omega(k, theta) surfaces (where k is the wave vector for a fixed angle of propagation) provide a clear picture of the behavior of cold plasma waves as the direction of propagation is varied. The group velocity (dw\\/dk) has a simple geometrical

M. E. Oakes; R. B. Michie; K. H. Tsui; J. E. Copeland

1979-01-01

178

Plasma klystron amplifier  

NASA Astrophysics Data System (ADS)

A body of dense plasma is established within a short drift tube of a klystron amplifier between input and output resonator cavities thereof to support current modulation of microwave energy by interaction with an electron beam propagated through the drift tube. The plasma is confined to a column radially spaced from the electron beam for two-stream interaction enabling enhancement of current modulation under simultaneous high-power and high frequency operation.

Uhm, Han S.

1993-05-01

179

Plasma klystron amplifier  

NASA Astrophysics Data System (ADS)

A body of dense plasma is established within a short drift tube of a klystron amplifier between input and output resonator cavities thereof to support current modulation of microwave energy by interaction with an electron beam propagated through the drift tube. The plasma is confined to a column radially spaced from the electron beam for two-stream interaction enabling enhancement of current modulation under simultaneous high-power and high frequency operation.

Uhm, Han S.

1995-01-01

180

The plasma scalpel.  

PubMed

The plasma scalpel simultaneously cuts tissue and cauterizes blood vessels measuring 3 mm in diameter with a small, hot (3000 C) gas jet. In animal studies, the amount of hemorrhage has been shown to be less with the plasma scalpel than with steel or electrosurgical scalpels, and incisions have healed without complications. Amount of damaged tissue is limited. Human trials are under way, and the device shows promise as a clinical tool. PMID:1018700

Link, W J; Incropera, F P; Glover, J L

1976-01-01

181

Voriconazole plasma monitoring  

Microsoft Academic Search

Aims:Very little information is available regarding the use of voriconazole drug monitoring in children with invasive fungal infections. The purpose of this study was to report the cases of five paediatric patients treated with voriconazole, in which plasma levels were used to monitor therapy.Methods:Five children treated with voriconazole were included in this case series. Voriconazole plasma levels were determined using

A C Pasqualotto; M Shah; R Wynn; D W Denning

2008-01-01

182

Fueling by coaxial plasma guns  

Microsoft Academic Search

A review of the operational characteristics of ''snowplow'' and ''deflagration'' coaxial plasma guns is given. The injection of these plasmas into containment fields is discussed. The effect of a background plasma on low-beta injection is mentioned. The use of high-beta injection for reactor plasmas is described. (MOW)

1977-01-01

183

Plasma-based accelerator structures  

SciTech Connect

Plasma-based accelerators have the ability to sustain extremely large accelerating gradients, with possible high-energy physics applications. This dissertation further develops the theory of plasma-based accelerators by addressing three topics: the performance of a hollow plasma channel as an accelerating structure, the generation of ultrashort electron bunches, and the propagation of laser pulses is underdense plasmas.

Schroeder, Carl B.

1999-12-01

184

Dust phenomena in processing plasmas  

Microsoft Academic Search

Dust phenomena in processing plasmas are reviewed from the new viewpoint of birth of material in the plasma. The gas-phase growth of particles has been extensively studied for Si4 RF plasmas. The Si particles usually grow through three distinctive stages: an initial growth phase up to about 10 nm, whose size is between size ranges dominated by plasma properties and

Yukio Watanabe

1997-01-01

185

Light ion helicon plasma sources  

Microsoft Academic Search

Helicon plasma sources are capable of producing high density plasma using steady state solenoid or mirror-like magnetic fields with a wide variety of gases. Power to produce the plasma is supplied by various antenna configurations driven at frequencies typically ranging from 1 to 50 MHz. The ability to obtain high plasma densities with high fractional ionization using readily available, low-cost

M. D. Carter; F. W. Baity; R. H. Goulding; E. F. Jaeger; F. R. Chang-Díaz; J. P. Squire

2001-01-01

186

ITER plasma-facing components  

Microsoft Academic Search

The ITER plasma-facing components directly face the thermonuclear plasma and include the divertor, the blanket and the test blanket modules with their corresponding frames.The divertor is located at the bottom of the plasma chamber and is aimed at exhausting the major part of the plasma thermal power (including alpha power) and at minimising the helium and impurity content in the

Mario Merola; D. Loesser; A. Martin; P. Chappuis; R. Mitteau; V. Komarov; R. A. Pitts; S. Gicquel; V. Barabash; L. Giancarli; J. Palmer; M. Nakahira; A. Loarte; D. Campbell; R. Eaton; A. Kukushkin; M. Sugihara; F. Zhang; C. S. Kim; R. Raffray; L. Ferrand; D. Yao; S. Sadakov; A. Furmanek; V. Rozov; T. Hirai; F. Escourbiac; T. Jokinen; B. Calcagno; S. Mori

2010-01-01

187

Inductively coupled helium plasma torch  

DOEpatents

An inductively coupled plasma torch including a base member, a plasma tube and a threaded insert member within the plasma tube for directing the plasma gas in a tangential flow pattern. The design of the torch eliminates the need for a separate coolant gas tube. The torch can be readily assembled and disassembled with a high degree of alignment accuracy.

Montaser, Akbar (Potomac, MD); Chan, Shi-Kit (Washington, DC); Van Hoven, Raymond L. (Alexandria, VA)

1989-01-01

188

Solar and Fusion Plasmas  

SciTech Connect

The poster describes work I have published with co-authors in theoretical and experimental studies of plasmas: both in the laboratory, with relevance to magnetically confined fusion, and naturally occurring, in the Sun's atmosphere (the corona). In the case of fusion plasmas, recent work on recombining plasmas in a linear plasma device, the ULS, is described, which develops understanding of the processes by which detachment is obtained in a tokamak divertor. Results of experimental studies of recombining plasmas are presented, interpreted through 1D plasma models and collisional-radiative models. In the case of the solar corona, we discuss coronal heating by magnetic reconnection. The question of how the solar corona is heated to temperatures of millions of degrees is a major outstanding problem in astrophysics. Some recent results of numerical simulation of forced magnetic reconnection are presented, focusing on the energy release, and we describe how relaxation theory can be used to calculate heating by multiple reconnection events. The presence of high-energy charged particles is an important diagnostic of magnetic reconnection, and models of particle acceleration by reconnecting fields are also presented.

Browning, Philippa [School of Physics and Astronomy, University of Manchester (United Kingdom)

2005-10-17

189

Plasma acceleration of particle beams  

SciTech Connect

Plasmas, being fully ionized gases, are immune from electrical breakdown and so can support ultra-high accelerating fields (order GeV/cm) in the form of relativistic plasma waves. Several schemes to excite these waves and use them for particle acceleration are reviewed in this article. These include the beat wave accelerator (laser driven) and the plasma wakefield transformer (particle beam driven). In addition, the possible use of plasmas to provide strong final focusing of beams (the plasma lens) is described.

Katsouleas, T.; Dawson, J. M.

1989-04-05

190

Plasma scattering of electromagnetic radiation  

Microsoft Academic Search

The scattered power spectrum is considered along with aspects of incoherent scattering, constraints on scattering experiments, optical systems, the theory concerning the scattered spectrum for a low-temperature plasma, and questions of scattering from a low-temperature stable plasma. Attention is also given to scattering from a magnetized plasma, scattering from a high-temperature plasma, scattering from unstable plasmas, the kinetic theory of

J. Sheffield

1975-01-01

191

Plasma dynamics in DUSTWHEEL  

NASA Astrophysics Data System (ADS)

The new experiment DUSTWHEEL consists of a set of 24 water-cooled magnets, which produce a steady-state magnetic field of B <= 0.7T that is homogeneous over a length of L = 1 m. DUSTWHEEL has a special design for the investigation of drift or flute modes under the influence of a dusty plasma environment. In contrast to other plasma constituents dust particles are strongly affected by gravitation. To deal with this the magnets of DUSTWHEEL are suspended in a wheel-shaped cage, which allows tilting the entire experiment. In this way, the angle between the magnetic field direction and gravity can be chosen at will. This allows exciting dust flows by a variation of the residual component of gravity. The plasma in DUSTWHEEL is produced by means of a capacitive high frequency discharge at 13.56 MHz. The low density plasma has a Gaussian shaped density profile with a peak density of 4 10^14 m-3. The electron temperature is nearly constant with a value of circa 4 eV. A detailed analysis of density and potential fluctuations using Langmuir probes shows a turbulent plasma state with almost no mode like behavior. As a control parameter to get different dynamic states a biasing voltage can be applied to the plasma. In this way the plasma can also be driven to mode-like states. Amplitude and structure Analysis reveals that the structures have drift wave dynamics. So, DUSTWHEEL is ready to put dust inside and study the modification of drift waves.

Greiner, F.; Knist, S.; Piel, A.

2007-11-01

192

Understanding helicon plasmas  

SciTech Connect

This paper presents a comprehensive overview of work on the helicon plasmas and also discusses various aspects of RF power deposition in such plasmas. Some of the work presented here is a review of earlier work on theoretical [A. Ganguli et al., Phys. Plasmas 14, 113503 (2007)] and experimental [A. Ganguli et al., Plasma Sources Sci. Technol. 20(1), 015021 (2011)] investigations on helicon plasmas in a conducting cylindrical waveguide for m = -1 mode. This work also presents an approach to investigate the mechanisms by which the helicon and associated Trivelpiece-Gould (TG) waves are responsible for RF power deposition in Helicon discharges. Experiment design adopts the recent theory of damping and absorption of Helicon modes in conducting waveguides [A. Ganguli et al., Phys. Plasmas 14, 113503 (2007)]. The effort has also been made to detect the warm electrons, which are necessary for ionization, because Helicon discharges are of high density, low T{sub e} discharges and the tail of the bulk electron population may not have sufficient high-energy electrons. Experimental set up also comprises of the mirror magnetic field. Measurements using RF compensated Langmuir probes [A. Ganguli et al., Plasma Sources Sci. Technol. 17, 015003 (2008)], B-dot probe and computations based on the theory shows that the warm electrons at low pressure (0.2-0.3 mTorr) Helicon discharges, are because of the Landau damping of TG waves. In collisional environment, at a pressure Almost-Equal-To 10 mTorr, these high-energy electrons are due to the acceleration of bulk electrons from the neighboring regions across steep potential gradients possibly by the formation of double layers.

Tarey, R. D. [Department of Physics, Indian Institute of Technology, New Delhi 110016 (India); Sahu, B. B. [Department of Applied Sciences and Humanities, Dronacharya College of Engineering, Gurgaon 123506 (India); Ganguli, A. [Centre for Energy Studies, Indian Institute of Technology, New Delhi 110016 (India)

2012-07-15

193

Plasma plume propagation characteristics of pulsed radio frequency plasma jet  

SciTech Connect

A 4 cm long helium cold atmospheric pressure plasma jet with pulsed radio frequency (rf) excitation was obtained by a copper electrode inside a quartz tube. The plasma bullet propagation characteristics common to the microseconds direct current pulse and kilohertz plasma jet is not observed in this case. The space-, time-, and wavelength-resolved optical emission profiles suggest the pulsed rf plasma channel out of the tube was strengthened by ions and metastables with longer life time than the rf period, and the plasma propagation was actually an illumination of the plasma channel caused by energetic electrons accelerated along the channel.

Liu, J. H.; Liu, X. Y.; Hu, K.; Liu, D. W.; Lu, X. P. [Advanced Electromagnetic Engineering and Technology Laboratory, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China); Iza, F.; Kong, M. G. [Department of Electronic and Electrical Engineering, Loughborough University, Leicestershire LE11 3TU (United Kingdom)

2011-04-11

194

Plasma-surface interactions  

NASA Astrophysics Data System (ADS)

Materials processing is at a crossroads. Currently a large fraction of industrially viable materials processing is via plasmas. Until recently it has been economical to just examine the influence the plasma properties on the desired surface processes and through this ultimately optimize manufacturing. For example, it is well known that the surface processes (etch or deposition), occur in the top few mono-layers of the surface. Thus, in film growth one requires that molecules from the gas-phase land and bond on the surface. However as processing has reached the nano-scale, development of viable processes has become more and more difficult. In part, this is because of all of the free parameters that exist in plasmas. To overcome this economic issue, tool vendors and semiconductor companies have turned to complex computational models of processing plasmas. For those models to work, one requires a through understanding of all of the gas-phase and surface-phase processes that are exhibited in plasmas. Unfortunately, these processes, particularly those at the surface, are not well understood. In this article we describe a viable model of the surface-phase based on cross sections for processes that occur. While originally developed of fluorocarbon systems, the model also appears to be applicable to hydrocarbon systems.

Goeckner, M. J.; Nelson, C. T.; Sant, S. P.; Jindal, A. K.; Joseph, E. A.; Zhou, B. S.; Padron-Wells, G.; Jarvis, B.; Pierce, R.; Overzet, L. J.

2008-10-01

195

Plasma Colloquium Travel Grant Program  

SciTech Connect

OAK B188 Plasma Colloquium Travel Grant Program. The purpose of the Travel Grant Program is to increase the awareness of plasma research. The new results and techniques of plasma research in fusion plasmas, plasma processing space plasmas, basic plasma science, etc, have broad applicability throughout science. The benefits of these results are limited by the relatively low awareness and appreciation of plasma research in the larger scientific community. Whereas spontaneous interactions between plasma scientists and other scientists are useful, a focused effort in education and outreach to other scientists is efficient and is needed. The academic scientific community is the initial focus of this effort, since that permits access to a broad cross-section of scientists and future scientists including undergraduates, graduate students, faculty, and research staff.

Hazeltine, R.D.

1998-09-14

196

Advances in Plasma Astrophysics (IAU S274)  

NASA Astrophysics Data System (ADS)

Preface; 1. Plasma astrophysics in the laboratory; 2. Interstellar, space and planetary plasmas; 3. Solar and stellar plasma; 4. Plasma around compact objects; 5. Observational and modelling programs for plasma astrophysics; 6. Plasmas in galaxies and galaxy clusters; 7. Plasma astrophysics in numerical simulations; Author index; Object index.

Bonanno, Alfio; de Gouveia Dal Pino, Elisabete; Kosovichev, Alexander G.

2011-08-01

197

Chapter 8: Plasma operation and control  

Microsoft Academic Search

The ITER plasma control system has the same functional scope as the control systems in present tokamaks. These are plasma operation scenario sequencing, plasma basic control (magnetic and kinetic), plasma advanced control (control of RWMs, NTMs, ELMs, error fields, etc) and plasma fast shutdown. This chapter considers only plasma initiation and plasma basic control. This chapter describes the progress achieved

Y. Gribov; D. Humphreys; K. Kajiwara; E. A. Lazarus; J. B. Lister; T. Ozeki; A. Portone; M. Shimada; A. C. C. Sips; J. C. Wesley

2007-01-01

198

Physics of Radio-Frequency Plasmas  

NASA Astrophysics Data System (ADS)

1. Introduction; 2. Plasma dynamics and equilibrium; 3. Bounded plasmas; 4. Radiofrequency sheaths; 5. Single frequency capacitively-coupled plasmas; 6. Multi-frequency capacitively-coupled plasmas; 7. Inductively-coupled plasmas; 8. Helicon plasmas; 9. Real plasmas; 10. Electrical measurements; Index.

Chabert, Pascal; Braithwaite, Nicholas

2011-02-01

199

Nanoparticle-Plasma Interactions in Dusty Argon-Hydrogen Plasmas  

NASA Astrophysics Data System (ADS)

We studied the role of hydrogen in altering the plasma-nanoparticle interactions in low pressure dusty Ar-H2 plasma. Most dusty plasmas in which particles form through chemical nucleation, are multi-component plasmas containing hydrogen. As hydrogen's ionization potential is close to that of argon, both gases may be ionized. The presence of the light mass hydrogen ions has the potential to modify the plasma and plasma-nanoparticle interactions. We developed a global model for dusty argon-hydrogen plasma. For given absorbed power, nanoparticle density, pressure, and chamber size, we solved the power balance, plasma species balance, and particle current balance equations. We included a system of rate equations for important argon-hydrogen plasma chemical reactions and obtained electron energy distribution function (EEDF) using ZDPlasKin. A trace amount of H2 gas in Ar discharge causes Ar^+, ArH^+, and H3^+ to be the dominant ions. Their relative densities are dependent on chamber pressure, gas composition, and the nanoparticle density. Increase in H2 gas fraction reduces the plasma density. The presence of light ions reduces the average particle charge. Electron collisions with hydrogen and with the nanoparticles affect the EEDF shape. Overall, we find that the presence of H2 in the discharge significantly alters the plasma properties and the fundamental plasma-nanoparticle interactions. This work was supported by the US Dept. of Energy Plasma Science Center and DOE grant DE/SC-0002391.

Kortshagen, Uwe; Mamunuru, Meenakshi

2012-10-01

200

Fundamentals of plasma simulation  

SciTech Connect

With the increasing size and speed of modern computers, the incredibly complex nonlinear properties of plasmas in the laboratory and in space are being successfully explored in increasing depth. Of particular importance have been numerical simulation techniques involving finite size particles on a discrete mesh. After discussing the importance of this means of understanding a variety of nonlinear plasma phenomena, we describe the basic elements of particle-in-cell simulation and their limitations and advantages. The differencing techniques, stability and accuracy issues, data management and optimization issues are discussed by means of a simple example of a particle-in-cell code. Recent advances in simulation methods allowing large space and time scales to be treated with minimal sacrifice in physics are reviewed. Various examples of nonlinear processes successfully studied by plasma simulation will be given.

Forslund, D.W.

1985-01-01

201

Plasma Equilibrium in Tokamaks  

SciTech Connect

The task of the theory of tokamak equilibrium is to determine the global magnetic confinement topology and physical characteristics of the underlying basic equilibrium state, which is assumed to be static (both [partial derivative]/[partial derivative]t = 0 and background velocity v{sub 0} = 0). This could be considered to be the most boring case of plasma behavior, viz. total absence of dynamics: a corresponding fluid dynamics problem hardly exists. The reason for our interest in this plasma state is the prospect of obtaining clean, abundant, and cheap energy from controlled thermonuclear fusion reactions. Of course, criticism and doubt immediately enter the mind after a statement like this. Nevertheless, let us study this plasma state, leaving questions like 'is there such a state at all?' and 'is it actually so desirable?' for later (Sec. 5)

Goedbloed, J.P. [FOM- Institute for Plasma Physics 'Rijnhuizen' (Netherlands)

2004-03-15

202

Plasma Simulation Program  

SciTech Connect

Many others in the fusion energy and advanced scientific computing communities participated in the development of this plan. The core planning team is grateful for their important contributions. This summary is meant as a quick overview the Fusion Simulation Program's (FSP's) purpose and intentions. There are several additional documents referenced within this one and all are supplemental or flow down from this Program Plan. The overall science goal of the DOE Office of Fusion Energy Sciences (FES) Fusion Simulation Program (FSP) is to develop predictive simulation capability for magnetically confined fusion plasmas at an unprecedented level of integration and fidelity. This will directly support and enable effective U.S. participation in International Thermonuclear Experimental Reactor (ITER) research and the overall mission of delivering practical fusion energy. The FSP will address a rich set of scientific issues together with experimental programs, producing validated integrated physics results. This is very well aligned with the mission of the ITER Organization to coordinate with its members the integrated modeling and control of fusion plasmas, including benchmarking and validation activities. [1]. Initial FSP research will focus on two critical Integrated Science Application (ISA) areas: ISA1, the plasma edge; and ISA2, whole device modeling (WDM) including disruption avoidance. The first of these problems involves the narrow plasma boundary layer and its complex interactions with the plasma core and the surrounding material wall. The second requires development of a computationally tractable, but comprehensive model that describes all equilibrium and dynamic processes at a sufficient level of detail to provide useful prediction of the temporal evolution of fusion plasma experiments. The initial driver for the whole device model will be prediction and avoidance of discharge-terminating disruptions, especially at high performance, which are a critical impediment to successful operation of machines like ITER. If disruptions prove unable to be avoided, their associated dynamics and effects will be addressed in the next phase of the FSP.

Greenwald, Martin

2011-10-04

203

The 2012 Plasma Roadmap  

NASA Astrophysics Data System (ADS)

Low-temperature plasma physics and technology are diverse and interdisciplinary fields. The plasma parameters can span many orders of magnitude and applications are found in quite different areas of daily life and industrial production. As a consequence, the trends in research, science and technology are difficult to follow and it is not easy to identify the major challenges of the field and their many sub-fields. Even for experts the road to the future is sometimes lost in the mist. Journal of Physics D: Applied Physics is addressing this need for clarity and thus providing guidance to the field by this special Review article, The 2012 Plasma Roadmap. Although roadmaps are common in the microelectronic industry and other fields of research and development, constructing a roadmap for the field of low-temperature plasmas is perhaps a unique undertaking. Realizing the difficulty of this task for any individual, the plasma section of the Journal of Physics D Board decided to meet the challenge of developing a roadmap through an unusual and novel concept. The roadmap was divided into 16 formalized short subsections each addressing a particular key topic. For each topic a renowned expert in the sub-field was invited to express his/her individual visions on the status, current and future challenges, and to identify advances in science and technology required to meet these challenges. Together these contributions form a detailed snapshot of the current state of the art which clearly shows the lifelines of the field and the challenges ahead. Novel technologies, fresh ideas and concepts, and new applications discussed by our authors demonstrate that the road to the future is wide and far reaching. We hope that this special plasma science and technology roadmap will provide guidance for colleagues, funding agencies and government institutions. If successful in doing so, the roadmap will be periodically updated to continue to help in guiding the field.

Samukawa, Seiji; Hori, Masaru; Rauf, Shahid; Tachibana, Kunihide; Bruggeman, Peter; Kroesen, Gerrit; Whitehead, J. Christopher; Murphy, Anthony B.; Gutsol, Alexander F.; Starikovskaia, Svetlana; Kortshagen, Uwe; Boeuf, Jean-Pierre; Sommerer, Timothy J.; Kushner, Mark J.; Czarnetzki, Uwe; Mason, Nigel

2012-06-01

204

Electromagnetic strong plasma turbulence  

SciTech Connect

The first large-scale simulations of continuously driven, two-dimensional electromagnetic strong plasma turbulence are performed, for electron thermal speeds 0.01c{<=}v{<=}0.57c, by integrating the Zakharov equations for coupled Langmuir and transverse (T) waves near the plasma frequency. Turbulence scalings and wave number spectra are calculated, a transition is found from a mix of trapped and free T eigenstates for v{>=}0.1c to just free eigenstates for v{<=}0.1c, and wave energy densities are observed to undergo slow quasiperiodic oscillations.

Melatos, A.; Jenet, F. A.; Robinson, P. A. [School of Physics, University of Melbourne, Parkville, VIC 3010 (Australia); Department of Physics and Astronomy, University of Texas at Brownsville, Brownsville, Texas 78520 (United States); School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

2007-02-15

205

Ultracold Plasma Imaging  

NASA Astrophysics Data System (ADS)

Ultracold Plasma Imaging C. E. Simien, P. Gupta, S. Laha, S. B. Nagel, T. C. Killian Department of Physics & Astronomy, Rice University;Houston, TX 77005 We image ultra-cold plasmas of Strontium (Sr) using laser light on the 2S1/2-2P1/2 transition in the Sr+ ion at 422nm. The light is produced by frequency doubling a diode-laser in a linear enhancement cavity for the infrared. The photons scattered from the ions are imaged with an intensified CCD camera. We will present details of the generation of 422nm light and results from the imaging.

Simien, Clayton; Gupta, Priya; Laha, Sampad; Nagel, Sarah; Killian, Thomas

2003-05-01

206

DUST-PLASMA INTERACTIONS  

SciTech Connect

The objective of our theoretical research under this grant over the past 3 years was to develop new understanding in a range of topics in the physics of dust-plasma interactions, with application to space and the laboratory. We conducted studies related to the physical properties of dust, waves and instabilities in both weakly coupled and strongly coupled dusty plasmas, and innovative possible applications. A major consideration in our choice of topics was to compare theory with experiments or observations, and to motivate new experiments, which we believe is important for developing this relatively new field. Our research is summarized, with reference to our list of journal publications.

Dr. M. Rosenberg

2010-01-05

207

Plasma fractionation issues.  

PubMed

Procurement and processing of human plasma for fractionation of therapeutic proteins or biological medicines used in clinical practice is a multi-billion dollar international trade. Together the private sector and public sector (non-profit) provide large amounts of safe and effective therapeutic plasma proteins needed worldwide. The principal therapeutic proteins produced by the dichotomous industry include gamma globulins or immunoglobulins (including pathogen-specific hyperimmune globulins, such as hepatitis B immune globulins) albumin, factor VIII and Factor IX concentrates. Viral inactivation, principally by solvent detergent and other processes, has proven highly effective in preventing transmission of enveloped viruses, viz. HBV, HIV, and HCV. PMID:19289290

Farrugia, Albert; Evers, Theo; Falcou, Pierre-Francois; Burnouf, Thierry; Amorim, Luiz; Thomas, Sylvia

2009-03-16

208

Plasma Facing Components  

NASA Astrophysics Data System (ADS)

Energy escapes from a magnetically confined plasma by convection and diffusion from closed flux regions to open field lines where it is transported to solid surfaces on the device walls. Particle and energy transport along the field lines is much more rapid than transport perpendicular to the field. This means the flux of power and particles on surfaces is quite narrow. Extremely high heat flux can be mitigated by tilting the plasma facing surface, spreading the magnetic field, and adding radiating impurities. Even so the peak heat flux can be in the range of 10-30 MW/m^2. While this heat flux can be removed by structures having adequate thermal conductivity and aggressive cooling, the existence of severe intermittent heat flux 10 to 100 times higher limits the choice of materials and heat sink design. Future fusion devices will have to operate successfully with particle fluence hundreds of times greater than existing devices, and fusion reactor grade plasmas will add energetic neutron damage to the picture. Advances in either materials or design of plasma facing components (PFCs) have had a profound effect on core plasma performance. Early advances relied on selection of carbon based materials that had good thermal conductivity and no melting rather than refractory metals. Carbon fiber reinforced carbon composites provided further performance improvement. Divertor plasmas allowed exploration of plasma sweeping and more effective particle control, but concentrated the heat flux onto a smaller region. Hydrogen retention in carbon is one of the challenges facing the next generation of fusion devices. Impurity shielding in divertor plasmas allows all metal PFCs to be considered. Engineering of high Z refractory metal PFCs with active cooling has matured for use on long pulse devices. Exploratory studies have shown that liquid PFCs may be able to remove high heat flux with no erosion or nuclear damage issues. The major issue for liquid surfaces is control of the magneto-hydrodynamic interaction between the liquid and the spatially and temporally varying fields in a fusion device. This paper will review the advances that have enabled fusion devices and examine the paths that are likely to meet the needs of future devices.

Ulrickson, Michael

2005-10-01

209

Some plasma aspects and plasma diagnostics of ion sources.  

PubMed

We consider plasma properties in the most advanced type of plasma ion sources, electron cyclotron resonance ion sources for highly charged ions. Depending on the operation conditions the plasma in these sources may be highly ionized, which completely changes its transport properties. The most striking difference to weakly ionized plasma is that diffusion will become intrinsically ambipolar. We further discuss means of plasma diagnostics. As noninvasive diagnostic methods we will discuss analysis of the ion beam, optical spectroscopy, and measurement of the x-ray bremsstrahlung continuum. From beam analysis and optical spectroscopy one may deduce ion densities, and electron densities and distribution functions as a mean over the line of sight along the axis (optical spectroscopy) or at the plasma edge (ion beam). From x-ray spectra one obtains information about the population of highly energetic electrons and the energy transfer from the driving electromagnetic waves to the plasma -- basic data for plasma modeling. PMID:18315191

Wiesemann, Klaus

2008-02-01

210

Plasma enhanced surface treatments using electron beam-generated plasmas  

Microsoft Academic Search

NRL has developed a ‘large area plasma processing system’ (LAPPS) utilizing a high energy (?2 keV) modulated electron beam to drive the plasma ionization. This system has been shown to be (1) efficient at producing plasma in any gas composition, (2) capable of producing low temperature plasma electrons (<0.5 eV) in high densities (109–1012 cm?3) and (3) scalable to large

D. Leonhardt; C. Muratore; S. G. Walton; R. A. Meger

2004-01-01

211

A contoured gap coaxial plasma gun with injected plasma armature  

Microsoft Academic Search

A new coaxial plasma gun is described. The long term objective is to accelerate 100-200 mug of plasma with density above 1017 cm-3 to greater than 200 km\\/s with a Mach number above 10. Such high velocity dense plasma jets have a number of potential fusion applications, including plasma refueling, magnetized target fusion, injection of angular momentum into centrifugally confined

F. Douglas Witherspoon; Andrew Case; Sarah J. Messer; Richard Bomgardner; Michael W. Phillips; Samuel Brockington; Raymond Elton

2009-01-01

212

Tomographic Investigation of Plasma Jets Produced by Multielectrode Plasma Torches  

Microsoft Academic Search

Recent advances in the development of new plasma torches rely on the use of multiple electrodes to improve plasma jet stability.\\u000a Examples are the Triplex, employing three cathodes and a single anode, and the Delta, which uses three anodes with a single\\u000a common cathode. To characterize the plasma jet produced by these plasma torches, initial experiments have been performed using

J. Schein; M. Richter; K. D. Landes; G. Forster; J. Zierhut; M. Dzulko

2008-01-01

213

Complex plasmas: I. complex plasmas as unusual state of matter  

Microsoft Academic Search

This paper opens a series of review papers devoted to the physics of the so-called complex plasmas. The review contains a\\u000a description of new physical phenomena met in dusty plasmas and complex plasmas. The term complex plasma is used for a state\\u000a where some components (dust) are in crystal or liquid state, while the others (electron, ions, and neutral atoms)

V. N. Tsytovich; G. E. Morfill; H. Thomas

2002-01-01

214

Thermal plasma processing of materials  

SciTech Connect

Emphasis has been on plasma synthesis of fine powders, plasma Chemical Vapor Deposition (CVD), on related diagnostics, and on modeling work. Since plasma synthesis as well as plasma CVD make frequent use of plasma jets, the beginning has been devoted of plasma jets and behavior of particulates injected into such plasma jets. Although most of the construction of the Triple-Torch Plasma Reactor (TTPR) has already been done, modifications have been made in particular modifications required for plasma CVD of diamond. A new reactor designed for Counter-Flow Liquid Injection Plasma Synthesis (CFLIPS) proved to be an excellent tool for synthesis of fine powders as well as for plasma CVD. An attempt was made to model flow and temperature fields in this reactor. Substantial efforts were made to single out those parameters which govern particle size, size distribution, and powder quality in our plasma synthesis experiments. This knowledge is crucial for controlling the process and for meaningful diagnostics and modeling work. Plasma CVD of diamond films using both reactors has been very successful and we have been approached by a number of companies interested in using this technology for coating of tools.

Pfender, E.; Heberlein, J.

1992-02-01

215

Impurity Content of Plasma Produced by a Coaxial Plasma Gun  

Microsoft Academic Search

The impurity content of plasmas produced by a coaxial plasma gun, while ; low, has generally been estimated by measurements of qualitative nature. Since ; impurities constitute the primary source of radiation loss and cooling, a study ; was made to explore this plasma property. (R.E.U.);

Harold P. Eubank

1963-01-01

216

Studies of Plasma Expelled from a Coaxial Plasma Gun  

Microsoft Academic Search

An experimental study of the plasma leaving a coaxial gun is described. The plasma shows a conical shape with a central axial pinch. When a radial magnetic field is applied at the muzzle of the gun, magnetized plasma rings are formed. Under certain conditions the central pinch shows a helical instability, resulting in a considerable increase of the poloidal magnetic

L. Lindberg; C. T. Jacobsen

1964-01-01

217

Complex plasma—the plasma state of soft matter  

Microsoft Academic Search

Complex plasma is the plasma state of soft matter which consists of weakly ionized gas (plasma) and highly charged microparticles. The microparticles are large enough to be visualized individually and their dynamics can be observed with great accuracy using simple video microscopic technique. These features allow to perform experiments with high temporal and spatial resolutions (in terms of the appropriate

Manis Chaudhuri; Sergei A. Khrapak; Gregor E. Morfill

2010-01-01

218

Complex plasma-the plasma state of soft matter  

Microsoft Academic Search

Complex plasma is the plasma state of soft matter which consists of weakly ionized gas (plasma) and highly charged microparticles. The microparticles are large enough to be visualized individually and their dynamics can be observed with great accuracy using simple video microscopic technique. These features allow to perform experiments with high temporal and spatial resolutions (in terms of the appropriate

Manis Chaudhuri; Sergei A. Khrapak; Gregor E. Morfill

2010-01-01

219

Plasma treatments and plasma deposition of polymers for biomedical applications  

Microsoft Academic Search

The aim of this review is to describe how biomaterial engineering processes, particularly in the field of polymer modifications for enhanced blood-compatibility, can take advantage of low-pressure plasma techniques. It will also be emphasized how a diagnostic approach on both plasma and surface reactions can lead to understand and control the chemistry of plasma processes.

Pietro Favia; Riccardo d’Agostino

1998-01-01

220

A low energy plasma flood gun using RF plasma formation  

Microsoft Academic Search

A plasma flood gun (PFG) system useful for 300 mm wafer has been developed by using an RF plasma for the medium current implanter EXCEED2300. To produce low energy electrons, the electron energy is filtered by magnetic fields. To eliminate dose shift, a low flow rate of Xe gas is adopted. A linear geometry of the plasma production source chamber

S. Sakai; N. Hamamoto; T. Ikejiri; M. Tanjyo

2000-01-01

221

LASER PLASMA: Resonant optical characteristics of an ultracold laser plasma  

NASA Astrophysics Data System (ADS)

We report a computer simulation study of light absorption, scattering and emission at 397 nm in an ultracold calcium ion plasma under resonant excitation. The results point to spectral asymmetry of light scattering, nonlinear absorption, and emission in the plasma. An approach is proposed for ultracold plasma diagnostics using resonant optical characteristics.

Kosarev, N. I.; Shaparev, N. Ya

2009-12-01

222

Neutral plasma oscillations.  

National Technical Information Service (NTIS)

We examine the conditions for the existence of spectrally stable neutral modes in a Vlasov-Poisson plasma and show that for stable equilibria of systems that have unbounded spatial domain, the only possible neutral modes are those with phase velocities th...

B. A. Shadwick P. J. Morrison

1993-01-01

223

Plasma based accelerators  

NASA Astrophysics Data System (ADS)

A plasma medium can support a variety of wave motions which may be useful for accelerating charged particles. For highly relativistic beams the longitudinal electrostatic wave is most suitable and may be driven by laser or by particle beams. The basic principles, limitations and prospects for these devices are discussed.

Evans, R. G.

1987-05-01

224

Plasma sodium and hypertension  

Microsoft Academic Search

Plasma sodium and hypertension. Dietary salt is the major cause of the rise in the blood pressure with age and the development of high blood pressure in populations. However, the mechanisms whereby salt intake raises the blood pressure are not clear. Existing concepts focus on the tendency for an increase in extracellular fluid volume (ECV), but an increased salt intake

Hugh E. de Wardener; Feng J. He; Graham A. MacGregor

2004-01-01

225

Plasma jet ignition device  

Microsoft Academic Search

An ignition device of the plasma jet type is disclosed. The device has a cylindrical cavity formed in insulating material with an electrode at one end. The other end of the cylindrical cavity is closed by a metal plate with a small orifice in the center which plate serves as a second electrode. An arc jumping between the first electrode

M. E. McIlwain; Z. Golenko; J. F. Grant; A. D. Wittstein

1985-01-01

226

NRL: Plasma Formulary.  

National Technical Information Service (NTIS)

The NRL Plasma Formulary originated over twenty ve years ago and has been revised several times during this period. The guiding spirit and person primarily responsible for its existence is Dr. David Book. I am indebted to Dave for providing me with the TE...

J. D. Huba

2004-01-01

227

Plasma heating in JET  

Microsoft Academic Search

Heating the JET plasma well above temperatures reached in the ohmic phase is the aim of the two additional heating systems planned for JET: ion cyclotron resonance heating (ICRF) and neutral beam injection (NBI). Operations with the latter started in February 1986, initially with hydrogen injection, up to a power level of 7 MW. ICRF power has been delivered to

A. Ainsworth; H. Altmann; R. J. Anderson; J. Arbez; D. Bartlett; W. Bailey; K. Behringer; E. Bertolini; P. Bertoldi; C. H. Best; V. Bhatnagar; R. J. Bickerton; G. Boissin; T. Bonicelli; S. Booth; A. Boschi; G. Bosia; M. Botman; H. Brelen; H. Brinkschulte; M. L. Browne; M. Brusati; T. Budd; M. Bures; P. Butcher; H. Buttgereit; D. Cacaut; C. Caldwell-Nichols; D. Campbell; J. Carwardine; G. Celentano; C. D. Challis; A. Cheetman; J. Christiansen; C. Christodoulopoulos; P. Chuilon; R. Claesen; J. P. Coad; M. Cooke; J. G. Cordey; W. Core; S. Corti; A. E. Costley; G. Cottrell; J. Dean; E. Deksnis; G. Deschamps; K. J. Dietz; J. Dobbing; S. E. Dorling; D. F. Duechs; G. Duesing; H. Duquenoy; L. de Kock; A. Edwards; W. Engelhardt; F. Erhorn; B. Eriksson; H. Falter; T. Hellsten; J. L. Hemmerich; R. Hemsworth; F. Hendriks; R. F. Herzog; L. Horton; J. How; M. Huart; A. Hubbard; M. Hugon; P. Jones; J. Kaeline; A. Kaellne; A. Kaye; B. E. Keen; M. Keilhacker; G. Kinahan; A. Konstantellos; P. Kupschus; P. Lallia; J. R. Last; N. Foden; C. Froger; K. Fullard; A. Galetsas; A. Gallacher; A. Gibson; R. D. Gill; A. Geode; A. Gondhalekar; N. A. Gottardi; C. Gowers; R. Granetz; B. Green; S. Gregoli; F. S. Griph; R. Haange; C. J. Hancock; P. Harbour; R. F. Herog; J. Kaellne; L. Lauro-Taroni; E. Lazzaro; R. C. Lobel; P. Lomas; M. Lorenzo-Gottardi; C. Lowry; G. Magyar; D. Maissonneir; M. Malacarne; V. Marchese; P. Massmann; P. McMullen; M. J. Mead; P. Meriguet; V. Merlo; S. Mills; P. Millward; A. Moissonnier; P. L. Mondini; P. Morgan; G. Murphy; M. F. Nave; L. Nickesson; P. Nielson; P. Noll; S. Nowak; W. Obert; B. Oliver; M. Olsson; J. O'Rourke; M. G. Pacco; J. Paillere; L. Pannacione; S. Papastergiou; D. Pasini; M. Pescatore; J. Planncoulaine; J. P. Poffe; R. Prentice; T. Raimondi; C. Raymond; P. H. Rebut; J. Removille; W. Riediker; R. Roberts; A. Rolfe; R. T. Ross; G. Sadler; J. Saffert; N. Salmon; A. Sand; A. Santagiustina; R. Saunders; M. Schmid; F. C. Schueller; K. Selin; R. Shaw; D. Sigournay; R. Simonini; P. Smeulders; L. Sonnerup; K. Sonnenberg; M. Stamp; C. A. Steed; D. Stork; P. E. Stott; T. E. Stringer; D. Summers; A. Tanga; A. Taroni; A. Terrington; A. Tesini; P. R. Thomas; E. Thompson; F. Tibone; R. Tivery; E. Usselmann; H. Van der Beken; M. Von Hellerman; J. E. Van Montfoort; T. Wade; C. Walker; B. A. Wallander; M. Walravens; K. Walter; M. L. Watkins; M. Watson; D. Webberley; J. Wesson; J. Wilks; T. Winkel; C. Woodward; M. Wykes; D. Young; L. Zennelili; J. Zwart; B. Beaumont; D. Gambier; D. Moreau; J. Ehrenberg; H. Jaeckel; S. Kissel; U. Kuephnapfel; R. Mueller; A. Staebler; A. Weller; J. H. Hamnen; M. Evrared; M. Gadeberg; K. Thomsen; P. Dupperrex; G. Tonetti; N. Lopez-Cardozo; B. Tubbing; J. Von Seggern; J. Tagle; F. Bombarda; G. Bracco; R. Giannella; R. Carolan; M. Cox; M. Forrest; D. Goodall; N. Hawkes; P. Haynes; J. Hugill; K. D. Lawson; G. McCracken; J. Partridge; N. Peacock; J. Snipes; T. Todd; H. Schamel; H. Summers; S. Tsuji; G. Tallents

1986-01-01

228

Filamentary magnetohydrodynamic plasmas  

SciTech Connect

A filamentary construct of magnetohydrodynamical plasma dynamics, based on the Elsasser variables was developed. This approach is modeled after discrete vortex models of hydrodynamical turbulence, which cannot be expected in general to produce results identical to ones based on a Fourier decomposition of the fields. In a highly intermittent plasma, the induction force is small compared to the convective motion, and when this force is neglected. the plasma vortex system is described by a Hamiltonian. For a system with many such vortices we present a statistical treatment of a collection of discrete current-vorticity concentrations. Canonical and microcanonical statistical calculations show that both the vorticity and the current spectra are peaked at long wavelengths, and the expected states revert to known hydrodynamical states as the magnetic field vanishes. These results differ from previous Fourier-based statistical theories. but it is found that when the filament calculation is expanded to include the inductive force, the results approach the Fourier equilibria in the low-temperature limit, and the previous Hamiltonian plasma vortex results in the high-temperature limit. Numerical simulations of a large number of filaments are carried out and support the theory. A three-dimensional vortex model is outlined as well, which is also Hamiltonian when the inductive force is neglected.

Kinney, R.; Tajima, T.; Petviashvili, N. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies; McWilliams, J.C. [National Center for Atmospheric Research, Boulder, CO (United States)

1993-05-01

229

Plasma Reinforced Ceramic Coatings.  

National Technical Information Service (NTIS)

The introduction of metal reinforcement (W, Mo) into the plasma ceramic Al2O3 coatings results in the following: increased strength of their adhesion to the substrate and a prolonged service life due to a firm contact ensured by welding the reinforcing el...

D. M. Karpinos V. G. Zilberberg V. S. Klimenko

1974-01-01

230

Plasma-Propellant Interactions.  

National Technical Information Service (NTIS)

This is the second in a series of reports on our research on Propellant-Plasma Interactions. The first report described our facilities for testing propellants at high pressures. This report covers the design, fabrication and testing of equipment for produ...

W. G. Proud P. Kalafatis J. E. Field

2002-01-01

231

Plasma-Propellant Interactions.  

National Technical Information Service (NTIS)

In one series of experiments, see Sections 1-6, plasma/propellant interactions were studied. Four different propellants (see Section 3) were placed at chosen distances from the discharge. The discharges were made either in a high pressure vessel or at amb...

W. G. Proud P. Kalafatis M. J. Gifford M. W. Greenaway C. Dobson

2003-01-01

232

Laser Plasma Accelerators  

NASA Astrophysics Data System (ADS)

The continuing development of powerful laser systems has permitted to extend the interaction of laser beams with matter far into the relativistic domain, and to demonstrate new approaches for producing energetic particle beams. The extremely large electric fields, with amplitudes exceeding the TV/m level, that are produced in plasma medium are of relevance particle acceleration. Since the value of this longitudinal electric field, 10,000 times larger than those produced in conventional radio-frequency cavities, plasma accelerators appear to be very promising for the development of compact accelerators. The incredible progresses in the understanding of laser plasma interaction physic, allows an excellent control of electron injection and acceleration. Thanks to these recent achievements, laser plasma accelerators deliver today high quality beams of energetic radiation and particles. These beams have a number of interesting properties such as shortness, brightness and spatial quality, and could lend themselves to applications in many fields, including medicine, radio-biology, chemistry, physics and material science,security (material inspection), and of course in accelerator science.

Malka, Victor

233

Plasma antioxidants from chocolate  

Microsoft Academic Search

There is some speculation that dietary flavonoids from chocolate, in particular (-)epicatechin, may promote cardiovascular health as a result of direct antioxidant effects or through antithrombotic mechanisms. Here we show that consumption of plain, dark chocolate (Fig. 1) results in an increase in both the total antioxidant capacity and the (-)epicatechin content of blood plasma, but that these effects are

Mauro Serafini; Rossana Bugianesi; Giuseppe Maiani; Silvia Valtuena; Simone De Santis; Alan Crozier

2003-01-01

234

PLASMA ANTIOXIDANT MEASUREMENTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Measures of in vivo antioxidant status are important in understanding the role of oxidative events in the initiation and progression of numerous diseases, including cancer, atherosclerosis, and diabetes. In vivo antioxidant status can be assessed by measuring individual plasma or tissue levels of an...

235

Implicit plasma simulation  

SciTech Connect

Implicit time integration methods have been used extensively in numerical modelling of slowly varying phenomena in systems that also support rapid variation. Examples include diffusion, hydrodynamics and reaction kinetics. This article discussed implementation of implicit time integration in plasma codes of the ''particle-in-cell'' family, and the benefits to be gained.

Langdon, A.B.

1985-03-03

236

Plasma boundaries and shocks  

Microsoft Academic Search

The quadrennium has seen an explosive growth in our knowledge and understanding of the various plasma and magnetic field boundaries in the terrestrial magnetosphere. Nowhere is that more evident than at the magneto pause and bow shock. In the 1975 and 1979 quadrennial reports, the magnetopause was covered in a single paragraph each year. The bow shock received one paragraph

C. T. Russell; E. W. Greenstadt

1983-01-01

237

Hydrodynamic equations for anisotropic plasma  

Microsoft Academic Search

Equations for anisotropic, partly ionized plasma in the ionosphere and plasmasphere are obtained to a 16-moment approximation. Also presented are expressions for the heat fluxes of transverse and longitudinal energy in a multicomponent plasma.

Iu. V. Konikov; V. I. Kuzivanov; G. V. Khazanov

1980-01-01

238

Efficient Generation of Volumetric Plasmas.  

National Technical Information Service (NTIS)

Sources that generate cubic meter volumes of plasma are of commercial importance for ionized gas chemistry, toxic waste remediation, and surface treatments. Efficient plasma production is necessary for minimizing the net power budget, system complexity, a...

R. J. Vidmar

1997-01-01

239

Electrostatic-Inertial Plasma Confinement.  

National Technical Information Service (NTIS)

The work was directed towards an answer to the question: 'How dense a plasma can be confined by electrostatic-inertial means.' Electrostatic-inertial plasma confinement consists of trapping charged particles in potential wells (of the electric field), whi...

T. J. Dolan J. T. Verdeyen B. E. Cherrington D. J. Meeker

1970-01-01

240

Solitons and Chaos in Plasma.  

National Technical Information Service (NTIS)

Plasma exhibits a full variety of nonlinear phenomena. Active research in nonlinear plasma physics contributed to explore the concepts of soliton and chaos. Structure of the soliton equations and the dynamics of low dimensional Hamiltonian systems are dis...

Y. H. Ichikawa

1991-01-01

241

Plasma physics: Order from disorder  

NASA Astrophysics Data System (ADS)

The formation of a macroscopic self-organized electromagnetic-field structure during a collisionless interaction of supersonic plasma streams is challenging existing models of counter-streaming plasmas.

Lebedev, Sergey

2012-11-01

242

Strong Beam-Plasma Turbulence.  

National Technical Information Service (NTIS)

High-power broadband microwave radiation was observed when an intense relativistic electron beam was injected into an unmagnetized gun-produced plasma. From spectroscopic measurements of hf strong electric fields in the plasma, it was found that our beam-...

M. Masuzaki R. Ando M. Yoshikawa K. Kobayashi H. Koguchi

1994-01-01

243

Plasma spectroscopy for magnetically confined fusion plasma  

SciTech Connect

An emission line of neutral helium {lambda}667.8 nm (21P-31D) is observed with a set of line of sights which covers an entire poloidal cross section of LHD, a heliotron-type fusion experimental device. From the observed Zeeman splittings and the well-known magnetic field structure in the plasma, the emission locations on the line of sight are precisely determined. The distribution of line emissions over the observed poloidal cross section is derived from the results of all the line of sights through a tomographic analysis.Balmer series lines of neutral hydrogen are measured for the rotating radiation body in the Serpens mode [J. Miyazawa et al., Nucl. Fusion 46, 532 (2006)]. The electron temperature and density are derived from the observed spectra with the help of calculations with the collisional-radiative (CR) model. The derived electron density is confirmed with the Stark broadening of several lines from n = 7 to 16 levels, where n is the principal quantum number.We have developed a CR model code for neutral helium based on recently calculated cross section data of electron impact. Six emission lines of neutral helium for the transitions from n = 3 to n = 2 levels are measured for various discharges in LHD and an estimation of the electron temperature and density is attempted from the intensity ratios among three lines, {lambda}667.7 nm (21P-31D), {lambda}706.5 nm (23P-33S), and {lambda}728.1 nm (21P-31S), out of the six lines. Intensities of other three lines, {lambda}388.9 nm (23S-33P), {lambda}501.6 nm (21S-31P), and {lambda}587.6 nm (23P-33D), are calculated with the derived plasma parameters and the agreement with the measured line intensities is found satisfactory.

Goto, M.; Morita, S. [National Institute for Fusion Science, Toki 509-5292 (Japan)

2007-04-06

244

Plasma model for charging damage  

NASA Astrophysics Data System (ADS)

The mechanism responsible for charging damage is treated as beam/plasma driven differences in local floating potentials on the process surface. A cold plasma flood is shown to limit these potential differences. Beam/plasma J-V characteristics obtained with CHARM2 in a high current implanter are fit with the theory. With flood OFF, the fit corresponds to plasma buildup over the target surface.

Vella, M. C.; Lukaszek, W.; Current, M. I.; Tripsas, N. H.

1994-07-01

245

Plasma Processing for Carbon Nanomaterials  

NASA Astrophysics Data System (ADS)

Plasma is a useful tool to synthesize carbon nano-materials including diamond, fullerene, nanotube and graphene. This review introduces the overview of these carbon nano-materials produced by thermal or non-thermal plasmas and also the authors' work related to plasma-enhanced chemical vapor deposition of carbon nanotubes and its correlation with numerical simulation of CH4/H2 feedstock gas plasmas. The amount of carbon atoms in the CNTs grown and that calculated from simulation showed good agreement.

Suda, Yoshiyuki; Takikawa, Hirofumi; Tanoue, Hideto

246

Thermal plasmas in material processing  

Microsoft Academic Search

Thermal plasmas are partially ionized gases at atmospheric pressures, characterized by temperatures in the range of 2000–20,000\\u000a K and charged particle number densities in the range of 1019–1021 per m3. Thermal plasmas are produced by plasma torches as a highly constricted jet. The high temperatures, enthalpies and heat fluxes\\u000a in the plasma jet make it amenable to many chemical and

N Venkatramani

1995-01-01

247

Magnetoacoustic solitons in quantum plasma  

SciTech Connect

Nonlinear magnetoacoustic waves in collisionless homogenous, magnetized quantum plasma is studied. Two fluid quantum magneto-hydrodynamic model (QMHD) is employed and reductive perturbation method is used to derive Korteweg de Vries (KdV) equation for magnetoacoustic waves. The effects of plasma density and magnetic field intensity are investigated on magnetoacoustic solitary structures in quantum plasma. The numerical results are also presented, which are applicable to explain some aspects of the propagation of nonlinear magnetoacosutic wave in dense astrophysical plasma situations.

Hussain, S.; Mahmood, S. [Theoretical Plasma Physics Division (TPPD), PINSTECH, P.O. Nilore, Islamabad (Pakistan); Department of Physics and Applied Mathematics (DPAM), PIEAS, P.O. Nilore, Islamabad (Pakistan)

2011-08-15

248

Human Plasma Protein C  

PubMed Central

Protein C is a vitamin K-dependent protein, which exists in bovine plasma as a precursor of a serine protease. In this study, protein C was isolated to homogeneity from human plasma by barium citrate adsorption and elution, ammonium sulfate fractionation, DEAE-Sephadex chromatography, dextran sulfate agarose chromatography, and preparative polyacrylamide gel electrophoresis. Human protein C (Mr = 62,000) contains 23% carbohydrate and is composed of a light chain (Mr = 21,000) and a heavy chain (Mr = 41,000) held together by a disulfide bond(s). The light chain has an amino-terminal sequence of Ala-Asn-Ser-Phe-Leu- and the heavy chain has an aminoterminal sequence of Asp-Pro-Glu-Asp-Gln. The residues that are identical to bovine protein C are underlined. Incubation of human protein C with human ?-thrombin at an enzyme to substrate weight ratio of 1:50 resulted in the formation of activated protein C, an enzyme with serine amidase activity. In the activation reaction, the apparent molecular weight of the heavy chain decreased from 41,000 to 40,000 as determined by gel electrophoresis in the presence of sodium dodecyl sulfate. No apparent change in the molecular weight of the light chain was observed in the activation process. The heavy chain of human activated protein C also contains the active-site serine residue as evidenced by its ability to react with radiolabeled diisopropyl fluorophosphate. Human activated protein C markedly prolongs the kaolin-cephalin clotting time of human plasma, but not that of bovine plasma. The amidolytic and anticoagulant activities of human activated protein C were completely obviated by prior incubation of the enzyme with diisopropyl fluorophosphate. These results indicate that human protein C, like its bovine counterpart, exists in plasma as a zymogen and is converted to a serine protease by limited proteolysis with attendant anticoagulant activity. Images

Kisiel, Walter

1979-01-01

249

HEMOGLOBIN AND PLASMA PROTEIN  

PubMed Central

Hemoglobin (presumably its essential protein globin), given intraperitoneally to a protein-fasting dog, will be used effectively to supply the protein requirements of the body. Nitrogen balance may thus be maintained for 20 days under favorable conditions. New hemoglobin and plasma protein will be formed related to hemoglobin injections in depleted dogs where there is urgent need for these proteins (anemia and hypoproteinemia). Obviously this calls for supplementary amino acids which in globin are low and we assume these amino acids must be contributed from body protein stores. Plasma proteins (in plasma) tested in the same manner are completely utilized with no loss of nitrogen, positive nitrogen balance, weight balance, and no change in the albumin-globulin ratios. Hemoglobin (globin) is less effectively utilized as compared with plasma protein given parenterally and there is some increase in urinary nitrogen above control periods. The albumin-globulin ratio may be somewhat modified by hemoglobin injections intraperitoneally. Hemoglobin (globin) digests contribute effectively to body maintenance of nitrogen equilibrium. These digests are about as effective as whole hemoglobin in maintaining nitrogen balance but cause a rise in undetermined nitrogen not seen when hemoglobin alone is given intraperitoneally. Pigment radicles derived from hemoglobin given intraperitoneally are thrown away and appear as surplus bile pigment even when there is urgent need for all available nitrogenous material—given protein fasting, anemia, and hypoproteinemia in a bile fistula dog. The body evidently prefers to make rather than conserve the pyrrol aggregate (pigment radicle). We assume that the injected hemoglobin (globin) or hemoglobin digests contribute to the body protein pool and from this pool various proteins emerge to supply protein requirements of tissue or organ cells or to produce new hemoglobin or plasma protein if needed. We have no explanation as to what determines the pattern of this protein flow but new hemoglobin is very high on the priority list.

Miller, L. L.; Robscheit-Robbins, F. S.; Whipple, G. H.

1945-01-01

250

Enhanced incoherent scatter plasma lines  

Microsoft Academic Search

Detailed model calculations of auroral second- ary and photoelectron distributions for varying conditions have been used to calculate the theoretical enhancement of incoherent scatter plasma lines. These calculations are compared with EISCAT UHF radar measurements of enhanced plasma lines from both the E and F regions, and published EISCAT VHF radar measurements. The agreement between the calculated and observed plasma

H. Nilsson; S. Kirkwood; J. Lilensten; M. Galand

1996-01-01

251

Plasma Crystallization of Silicon Nanoparticles  

NASA Astrophysics Data System (ADS)

Using nonthermal plasmas for synthesis of silicon nanocrystals is well-established. However, nanoparticle heating in the plasma, which leads to particle crystallinity, is poorly understood. The mechanism behind heating of these particles has only been studied through modeling. In-situ measurement of particle temperature during plasma processes is difficult, but particles themselves can serve as thermometers, as their crystallinity will change depending on heating in the plasma. Here we investigate the heating and crystallization of nanoparticles using a double-plasma configuration, examining both the particles and the plasma. Amorphous silicon nanoparticles are formed in a low-power plasma, then injected into a separate plasma which is operated with variable power. Nanoparticle characterization confirms that crystallization of the particles occurs at a threshold power to the secondary plasma, around 30W (nominal) for 5nm particles. Optical emission spectroscopy on the plasma provides estimates of the electron temperature during nanoparticle crystallization, and capacitive probe measurements reveal ion densities at varying plasma powers. We will compare our outcomes to previous modeling results to build a complete picture of nanoparticle heating in plasmas.

Anthony, Rebecca; Kramer, Nicolaas; Aydil, Eray; Kortshagen, Uwe

2012-10-01

252

Plasma Physics for Nuclear Fusion  

Microsoft Academic Search

The book focuses on the properties of gaseous plasmas needed in the attainment of controlled fusion reactions. The first five chapters develop the fundamentals of plasma physics and present the conditions of nuclear fusion reactions. The next four provide a magnetohydrodynamic description of plasmas, followed by four chapters that explain wave phenomena and instabilities by means of a kinetic model.

K. Miyamoto; Robert L. Dewar

1980-01-01

253

Modeling of magnetron sputtering plasmas  

Microsoft Academic Search

Partially ionized, low-temperature plasmas have been used extensively in many areas of technology. These applications of plasma include surface processing and lighting devices. There are three major categories in surface processing: sputtering, etching and surface modification. The examples of lighting device application are light bulbs, lasers and plasma display devices. In this discussion, simulation study of magnetron sputtering system are

C. H Shon; J. K Lee

2002-01-01

254

High-temperature plasma physics  

SciTech Connect

Both magnetic and inertial confinement research are entering the plasma parameter range of fusion reactor interest. This paper reviews the individual and common technical problems of these two approaches to the generation of thermonuclear plasmas, and describes some related applications of high-temperature plasma physics.

Furth, H.P.

1988-03-01

255

Plasma catalytic reforming of methane  

Microsoft Academic Search

Thermal plasma technology can be efficiently used in the production of hydrogen and hydrogen-rich gases from methane and a variety of fuels. This article describes progress in plasma reforming experiments and calculations of high temperature conversion of methane using heterogeneous processes. The thermal plasma is a highly energetic state of matter that is characterized by extremely high temperatures (several thousand

L Bromberg; D. R Cohn; A Rabinovich; N Alexeev

1999-01-01

256

Low-temperature plasma diagnostics  

Microsoft Academic Search

The work covers theory, methodology and instrumentation pertaining to the diagnostics - induction, spectroscopic, laser, microwave, etc. - of low temperature plasma. Particular papers are presented on such topics as investigation of plasma conductivity in MHD generator facilities, study of the parameters of a combustion-product plasma, measurements of shock-heated gas flow, and the use of a laser beam scanning method

E. M. Shelkov

1979-01-01

257

Antimatter Plasmas in the Laboratory  

Microsoft Academic Search

Progress in the ability to accumulate and cool positrons and antiprotons is enabling new scientific and technological opportunities. The driver for this work is plasma physics research - developing new ways to create and manipulate antimatter plasmas [1]. This talk presents an overview of the enabling plasma technology, recent physics results, and near-term goals and challenges. In atomic physics, new

Clifford M. Surko

2003-01-01

258

Solar array arcing in plasmas  

Microsoft Academic Search

Solar cells in space plasma conditions are known to arc into the plasma when the interconnects are at a negative potential of a few hundred volts, relative to plasma potential. For cells with silver-coated interconnects, a threshold voltage for arcing exists at about -230 V, as found in both ground and LEO experiments. The arc rate beyond the threshold voltage

Dale C. Ferguson

1990-01-01

259

TOPICAL REVIEW: Thermal plasma modelling  

Microsoft Academic Search

Electrical arcs and, more generally thermal plasmas, are widely used in many applications and the understanding or the improvement of the corresponding processes or systems, often requires precise modelling of the plasma. We present, here, a double approach to thermal plasma modelling, which combines the scientific procedure with an engineering point of view. First, we present the fundamental properties of

A. Gleizes; J. J. Gonzalez; P. Freton

2005-01-01

260

Radio Frequency Plasma in Water  

Microsoft Academic Search

We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000-4500 K. Spectroscopic measurements show

Tsunehiro Maehara; Hiromichi Toyota; Makoto Kuramoto; Atsushi Iwamae; Atsushi Tadokoro; Shinobu Mukasa; Hiroshi Yamashita; Ayato Kawashima; Shinfuku Nomura

2006-01-01

261

Plasma Turbulence Calculations On Supercomputers  

Microsoft Academic Search

To predict the size, expense, and performance of mag netic fusion reactors, it is critical to know the scaling of particle transport and losses across the magnetic field with machine and plasma parameters. The mechanism for transport in magnetically confined plasmas is not yet known. However, at the plasma edge, losses larger than those predicted by classical theory have been

B. A. Carreras; N. Dominguez; J. B. Drake; J.-N. Leboeuf; L. A. Charlton; J. A. Holmes; D. K. Lee; V. E. Lynch; L. Garcia

1990-01-01

262

Numerical simulation of dusty plasmas  

SciTech Connect

The numerical simulation of physical processes in dusty plasmas is reviewed, with emphasis on recent results and unresolved issues. Three areas of research are discussed: grain charging, weak dust-plasma interactions, and strong dust-plasma interactions. For each area, we review the basic concepts that are tested by simulations, present some appropriate examples, and examine numerical issues associated with extending present work.

Winske, D.

1995-09-01

263

Tomographic Investigation of Plasma Jets Produced by Multielectrode Plasma Torches  

NASA Astrophysics Data System (ADS)

Recent advances in the development of new plasma torches rely on the use of multiple electrodes to improve plasma jet stability. Examples are the Triplex, employing three cathodes and a single anode, and the Delta, which uses three anodes with a single common cathode. To characterize the plasma jet produced by these plasma torches, initial experiments have been performed using tomography in the visible range. Due to the improved stability of the plasma jet in the multielectrode configuration it is possible to carry out tomography by means of a regular charge-coupled device (CCD) camera, which is rotated around the plasma jet axis. The two-dimensional information obtained by the CCD camera is subsequently processed to produce an image of the three-dimensional emission distribution. The tomographic analysis is mated with a simple but effective simulation tool, which can be used as a basis for parameter-dependent multielectrode plasma torch design.

Schein, J.; Richter, M.; Landes, K. D.; Forster, G.; Zierhut, J.; Dzulko, M.

2008-09-01

264

Merging and splitting of plasma spheroids in a dusty plasma.  

PubMed

Dust particle growth in a plasma is a strongly disturbing phenomenon for the plasma equilibrium. It can induce many different types of low-frequency instabilities that can be experimentally observed, especially using high-speed imaging. A spectacular case has been observed in a krypton plasma where a huge density of dust particles is grown by material sputtering. The instability consists of well-defined regions of enhanced optical emission that emerge from the electrode vicinity and propagate towards the discharge center. These plasma spheroids have complex motions resulting from their mutual interaction that can also lead to the merging of two plasma spheroids into a single one. The reverse situation is also observed with the splitting of a plasma spheroid into two parts. These results are presented for the first time and reveal new behaviors in dusty plasmas. PMID:23368337

Mikikian, Maxime; Tawidian, Hagop; Lecas, Thomas

2012-12-14

265

Plasma dynamics in microsecond megaampere plasma opening switches  

SciTech Connect

The paper considers the transport of a magnetic field in highly ionized plasma of microsecond megaampere plasma opening switches. Self-similar solutions for plasma aggregation by a linearly increasing magnetic field are derived. For these solutions, the magnetic field energy in the current channel is much lower than the energy of the accelerated plasma flow. The effect of Joule heating of the plasma becomes profound only with a uniform current density. It is shown that the evolution of the magnetic field in the accelerated flow is reduced to diffusion with an effective electrical conductivity proportional to the harmonic average of the Spitzer conductivity and conductivity dependent on the magnetic field in the current channel. Thus, during about the first 100 ns of the current pulse the conductivity of the current channel increases due to the plasma heating and, as the plasma is accelerated, its conductivity decreases.

Loginov, S. V. [Institute of High Current Electronics SB RAS, Tomsk 634055 (Russian Federation)

2011-10-15

266

Interaction between electromagnetic waves and plasma waves in motional plasma  

SciTech Connect

The electromagnetic wave (EM wave) behavior and the electromagnetic instability caused by the interaction between an EM wave and a plasma wave in motional plasma are studied. The dispersion relation of EM waves and the dielectric tensor of motional plasma are derived by magnetohydrodynamics, and the wave phenomenon in motional plasma is displayed. As a result, the electromagnetic instability, which is excited by the interaction between the EM waves and the plasma waves, is revealed. The mechanism of the instability is the coupling between high frequency electromagnetic field and the transverse electron oscillation derived from the deflection of longitudinal electron oscillation due to self-magnetic field. The present research is useful with regard to the new type of plasma radiation source, ion-focusing accelerator, and plasma diagnostic technique.

Chen, S. Y.; Gao, M.; Tang, C. J. [College of Physical Science and Technology, Sichuan University, ChengDu 610065 (China); Peng, X. D. [Southwest Institution of Physics Center for Fusion Science, ChengDu 610041 (China)

2009-06-15

267

High beta plasma operation in a toroidal plasma producing device  

DOEpatents

A high beta plasma is produced in a plasma producing device of toroidal configuration by ohmic heating and auxiliary heating. The plasma pressure is continuously monitored and used in a control system to program the current in the poloidal field windings. Throughout the heating process, magnetic flux is conserved inside the plasma and the distortion of the flux surfaces drives a current in the plasma. As a consequence, the total current increases and the poloidal field windings are driven with an equal and opposing increasing current. The spatial distribution of the current in the poloidal field windings is determined by the plasma pressure. Plasma equilibrium is maintained thereby, and high temperature, high beta operation results.

Clarke, John F. (Oak Ridge, TN)

1978-01-01

268

Modelling of Complex Plasmas  

NASA Astrophysics Data System (ADS)

Nowadays plasmas are used for various applications such as the fabrication of silicon solar cells, integrated circuits, coatings and dental cleaning. In the case of a processing plasma, e.g. for the fabrication of amorphous silicon solar cells, a mixture of silane and hydrogen gas is injected in a reactor. These gases are decomposed by making a plasma. A plasma with a low degree of ionization (typically 10_5) is usually made in a reactor containing two electrodes driven by a radio-frequency (RF) power source in the megahertz range. Under the right circumstances the radicals, neutrals and ions can react further to produce nanometer sized dust particles. The particles can stick to the surface and thereby contribute to a higher deposition rate. Another possibility is that the nanometer sized particles coagulate and form larger micron sized particles. These particles obtain a high negative charge, due to their large radius and are usually trapped in a radiofrequency plasma. The electric field present in the discharge sheaths causes the entrapment. Such plasmas are called dusty or complex plasmas. In this thesis numerical models are presented which describe dusty plasmas in reactive and nonreactive plasmas. We started first with the development of a simple one-dimensional silane fluid model where a dusty radio-frequency silane/hydrogen discharge is simulated. In the model, discharge quantities like the fluxes, densities and electric field are calculated self-consistently. A radius and an initial density profile for the spherical dust particles are given and the charge and the density of the dust are calculated with an iterative method. During the transport of the dust, its charge is kept constant in time. The dust influences the electric field distribution through its charge and the density of the plasma through recombination of positive ions and electrons at its surface. In the model this process gives an extra production of silane radicals, since the growth of dust is not included. Results are presented for situations in which the dust signi_cantly changes the discharge characteristics, both by a strong reduction of the electron density and by altering the electric field by its charge. Simulations for dust with a radius of 2 mu-m show that the stationary solution of the dust density and the average electric field depend on the total amount of the dust. The presence of dust enhances the deposition rate of amorphous silicon 2 at the electrodes because of the rise in the average electron energy associated with the decrease of the electron density and the constraint of a constant power input. This increase of deposition rate has also been observed in experiments by others. To study the behavior of dust in a less complicated environment, experiments in non-reactive plasmas have been carried out by a number of research groups. In these experiments the dust particles are injected through the electrodes in an argon discharge. These experiments have shown very interesting phenomena. Dust particles start to interact with each other in the discharge and form two-dimensional Coulomb clusters. These experiments often show an appearance of a void, a dustfree region in the discharge. Similar experiments have also been carried out under microgravity. These experiments have shown three-dimensional Coulomb clusters of dust particles also with the appearance of a void. Also rotating dust clouds (vortices) near the edges of the electrodes have been observed, that tend to rotate as long as the plasmas is on. To understand the behavior of the particles, we have developed a two-dimensional fluid model for a dusty argon plasma in which the plasma and dust parameters are solved self-consistently to study the behavior of dust particles. Simulations for dust with a radius of 7.5 mu-m show that a double space charge layer is created around the sharp boundary of the dust crystal. The inter-particle interaction is taken into account by means of an equation of state for the dust. A central dust-free region (void) is created by the ion drag force. The con

Akdim, Mohamed Reda

2003-09-01

269

Electrical potential measurement in plasma columns of atmospheric plasma jets  

NASA Astrophysics Data System (ADS)

The electrical potential of plasma generated from an atmospheric plasma jet device with Ar or He gas is measured with a high voltage probe in a plasma column inside a tube as well as in the plasma ejected through the open end of the tube. When the double plasma jet devices with Ar-gas are operated by the opposite polarities of an ac voltage with a few kV at both ends of a glass tube, the electrical potential of plasma column is high at both ends of the column, while the electrical potential in the middle of the plasma column is a few tens of volts. When the plasma column is formulated with the double plasma jets of a high voltage electrode at one end of the glass tube and a grounded electrode at the other end of the tube, the plasma column potential decreases linearly from a high voltage to a very low value, as the measurement position moves from the side of high voltage to the grounded location. In the double plasma jets of He-gas operated by high voltages in opposite polarities, the ejected plasma jets are attractive to each other at the intersection, merging together and having the electrical potential of a few tens of volts. On the other hand, if the two plasma jet columns are operated by high voltages of same polarity the ejected plasma jets are repulsive to each other at the intersection, having the electrical potential of a few hundreds of volts and causing an electrical shock.

Cho, Gunagsup; Kim, Junghyun; Kang, Hanlim; Kim, Yunjung; Kwon, Gi-Chung; Uhm, Han S.

2012-11-01

270

Resonant-cavity antenna for plasma heating  

Microsoft Academic Search

This patent describes a magnetic confinement plasma device having a plasma. The plasma is immersed in a strong magnetic field and confined within an evacuated plasma chamber. A wave launcher for launching electromagnetic waves in the range of frequencies of 10 MHz to 200 MHz energizes and thereby heats the plasma. The wave launcher is spaced-apart from the plasma. The

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

1987-01-01

271

Experimental Studies of Coaxial Plasma Gun Current  

Microsoft Academic Search

In this investigation of a coaxial plasma gun, plasma sheath currents and related behavior are examined. Plasma behavior in the gun affects gun characteristics. Plasma gun applications are determined by the plasma behavior. The AFWL PUFF capacitor bank (72 mu F, 29 nH, 120 kV) drives the plasma gun using a deuterium fill gas. The gas breakdown site is isolated

David Wayne Price

1988-01-01

272

Plasma processing and synthesis of materials  

SciTech Connect

These proceedings compile papers about plasma. Topics include: Plasma arc spraying, vacuum melting, plasma melters for nuclear waste vitrification, thermal degradation of metal oxides in plasma, electrohydrodynamics, laser-induced fluorescence, measurements of temperature in plasma, and modeling and diagnostics in plasma processing.

Apelian, D.; Szekely, J.

1987-01-01

273

Closed inductively coupled plasma cell  

DOEpatents

A closed inductively coupled plasma cell generates a relatively high power, low noise plasma for use in spectroscopic studies is disclosed. A variety of gases can be selected to form the plasma to minimize spectroscopic interference and to provide a electron density and temperature range for the sample to be analyzed. Grounded conductors are placed at the tube ends and axially displaced from the inductive coil, whereby the resulting electromagnetic field acts to elongate the plasma in the tube. Sample materials can be injected in the plasma to be excited for spectroscopy. 1 fig.

Manning, T.J.; Palmer, B.A.; Hof, D.E.

1990-11-06

274

Particle Simulation of Dusty Plasmas  

NASA Astrophysics Data System (ADS)

The NRL Dynamically Shielded Dust (DSD) particle simulation code has been developed to model dusty plasmas. The code uses the techniques of molecular dynamics, particle-in-cell plasma simulations, and the test particle formulation of plasma kinetic theory. In addition, the interaction potential between dust particles is broken into long and short range parts using the P3M technique of Hockney and Eastwood. The resulting simulation code avoids the necessity of integrating on plasma time scales, but still is able to include plasma effects.

Joyce, G.; Lampe, M.; Ganguli, G.

275

Plasma beat-wave accelerator  

SciTech Connect

We perform an analytic study of some quantities relevant to the plasma beat-wave accelerator (PBWA) concept. We obtain analytic expressions for the plasma frequency, longitudinal electron velocity, plasma density and longitudinal plasma electric field of a nonlinear longitudinal electron plasma oscillation with amplitude less than the wave-breaking limit and phase velocity approaching the speed of light. We also estimate the luminosity of a single-pass e/sup +/e/sup -/ linear PBWA collider assuming the energy and collision beamstrahlung are fixed parameters.

Noble, R.J.

1983-06-01

276

Ecr Plasma Modified Polysulfone Membranes  

NASA Astrophysics Data System (ADS)

This study considers ion transport properties of membranes modified by action of ECR nitrogen plasma. The membranes are a kind of polysulfone membrane. They generally used for ion transportation and recovery. These membranes were pretreated to remove impurities. We showed that ECR nitrogen plasma changes various kinds of surface functionalities. Ion transport properties of membranes were taken into consideration. IR measurements of both non plasma modified and plasma modified membranes were taken between 4000-400cm-1 scale. Additionally, they were characterized by scanning electron microscopy (SEM). During laboratory experiments, plasma treated membranes react much more better than their untreated analogues to ion transportation.

Kir, Esengul; Oksuz, Lutfi; Gok, Aysegul; Helhel, Selcuk

2004-09-01

277

Closed inductively coupled plasma cell  

DOEpatents

A closed inductively coupled plasma cell generates a relatively high power, low noise plasma for use in spectroscopic studies. A variety of gases can be selected to form the plasma to minimize spectroscopic interference and to provide a electron density and temperature range for the sample to be analyzed. Grounded conductors are placed at the tube ends and axially displaced from the inductive coil, whereby the resulting electromagnetic field acts to elongate the plasma in the tube. Sample materials can be injected in the plasma to be excited for spectroscopy.

Manning, Thomas J. (Gainesville, FL); Palmer, Byron A. (Los Alamos, NM); Hof, Douglas E. (Santa Fe, NM)

1990-01-01

278

Spectra of plasma turbulence, particle acceleration and heating by plasma waves in the interacting plasma  

Microsoft Academic Search

The present state of weak and strong plasma turbulence and plasma heating by waves is reviewed, with emphasis on the exact solutions of the wave kinetic equations, such as the power-law Kolmogorov spectra and streamers in k-vector space. The strong plasma turbulence generated by the modulational instability of linearly excited waves and their collapse is represented by strong Langmuir turbulence.

A. A. Galeev

1989-01-01

279

Spectra of plasma turbulence, particle acceleration and heating by plasma waves in the interacting plasma  

Microsoft Academic Search

The present state of weak and strong plasma turbulence and plasma heating by waves are reviewed, with emphasis on the exact solutions of the wave kinetic equations, such as the power-law Kolmogorov spectra and streamers in k-space. The strong plasma turbulence generated by the modulational instability of linearly excited waves and their collapse is represented by strong Langmuir turbulence. Because

A. A. Galeev

1989-01-01

280

Transport processes in space plasmas  

SciTech Connect

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project represents a comprehensive research effort to study plasma and field transport processes relevant for solar-terrestrial interaction, involving the solar wind and imbedded magnetic field and plasma structures, the bow shock of the Earth`s magnetosphere and associated waves, the Earth`s magnetopause with imbedded flux rope structures and their connection with the Earth, plasma flow in the Earth`s magnetotail, and ionospheric beam/wave interactions. The focus of the work was on the interaction between plasma and magnetic and electric fields in the regions where different plasma populations exist adjacent to or superposed on each other. These are the regions of particularly dynamic plasma behavior, important for plasma and energy transport and rapid energy releases. The research addressed questions about how this interaction takes place, what waves, instabilities, and particle/field interactions are involved, how the penetration of plasma and energy through characteristic boundaries takes place, and how the characteristic properties of the plasmas and fields of the different populations influence each other on different spatial and temporal scales. These topics were investigated through combining efforts in the analysis of plasma and field data obtained through space missions with theory and computer simulations of the plasma behavior.

Birn, J.; Elphic, R.C.; Feldman, W.C. [and others

1997-08-01

281

Plasma and the universe  

SciTech Connect

Hannes Alfven has enjoyed a long and spectacular career in which he has time and again pioneered the path that other workers were able fruitfully to exploit. One thinks of the Alven waves, the concept of gyrocenter drift and the perturbation theory based on it, and the critical velocity phenomenon in the interaction of a plasma with a neutral gas. All of these discoveries have been of fundamental importance. By no means content to rest on his laurels, Alfven has, during the last decade, contributed to science in a major sense, especially in the field of cosmogeny. For example, he has used the latest data from the Voyager spacecraft to test his detailed predictions of the structure of the Saturnian rings. Alfven's current preoccupation is with the Plasma Universe and, as may be expected, some of his concepts are receiving observational support, while others are still controversial.

Falthammar, C.G. (Royal Inst. of Technology, Stockholm (SE))

1988-01-01

282

Plasma Temperatures at Mars  

NASA Astrophysics Data System (ADS)

Ion and electron temperatures in the ionosphere of Mars affect plasma densities. These quantities vary with altitude and time of day. Modeling results are used to interpret existing measurements and to support anticipated MAVEN measurements. A 1D fluid model of the Martian ionosphere has been coupled to a kinetic supra-thermal electron transport model in order to self-consistently calculate ion and electron densities and temperatures. The models include diurnal variations, revealing hundreds of Kelvin changes in dayside electron and ion temperatures at fixed altitude. The models treat each ion species separately, revealing hundreds of Kelvin differences between H+ and O2+ temperatures. Consistent with previous studies using single-ion plasma, solar EUV heating alone is insufficient to heat the thermal electrons and ion species to observed temperatures, indicating the presence of additional heating sources.

Mayyasi-Matta, Majd; Mendillo, M.; Galand, M.; Moore, L.; Withers, P.

2013-10-01

283

Plasma jet takes off.  

PubMed

Thanks to a series of joint research projects by Los Alamos National Laboratory, Beta Squared of Allen, Texas, and the University of California at Los Angeles, there is now a more environmentally sound method for cleaning semiconductor chips that may also be effective in cleaning up chemical, bacterial, and nuclear contaminants. The Atmospheric Pressure Plasma Jet uses a type of ionized gas called plasma to clean up contaminants by binding to them and lifting them away. In contrast to the corrosive acids and chemical solvents traditionally used to clean semiconductor chips, the jet oxidizes contaminants, producing only benign gaseous by-products such as oxygen and carbon dioxide. The new technology is also easy to transport, cleans thoroughly and quickly, and presents no hazards to its operators. PMID:10417375

Frazer, L

1999-08-01

284

Simulations of Ultracold Plasmas  

NASA Astrophysics Data System (ADS)

Ultracold plasmas are formed by the laser photo-ionization of clusters of laser-cooled ions. [S. Kulin, T. C. Killian, S. D. Bergeson, and S. L. Rolston, Phys. Rev. Lett. 85, 318 (2000).] The laser-cooled atoms are localized in a small region (rms radius typically 200 ?m) with a very low temperature (as low as 10 ?K). The frequency and intensity of the ionizing laser can be varied, so that initial electron energies can range from 0.1 K to 1000 K, with peak electron densities ranging from 10^5 to 10^9 cm-3. Using a variety of techniques, we simulate the prompt electron loss and the plasma oscillations excited, the evaporative electron loss, and the electron thermalization via electron-ion and electron-electron collisons. We also investigate the electron temperature evolution and electron loss during the free expansion (Coulomb explosion) of the electron-ion cloud.

Hanson, J. D.; Robicheaux, F.

2001-10-01

285

Radio Frequency Plasma in Water  

NASA Astrophysics Data System (ADS)

We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000-4500 K. Spectroscopic measurements show that hydrogen and oxygen are excited in the plasma. The plasma is also obtained in tap water or NaCl solution with a high conductivity. In the solution, sodium spectral lines are observed. Colored water containing methylene blue is exposed to the plasma. The absorbence spectra of the colored water before and after exposure to the plasma suggest the decomposition of organic matter due to chemical reactions involving active species, such as OH-radicals.

Maehara, Tsunehiro; Toyota, Hiromichi; Kuramoto, Makoto; Iwamae, Atsushi; Tadokoro, Atsushi; Mukasa, Shinobu; Yamashita, Hiroshi; Kawashima, Ayato; Nomura, Shinfuku

2006-11-01

286

Hot plasmas in the magnetosphere  

NASA Astrophysics Data System (ADS)

The dynamics and properties of plasmas of energies from a few tens of eV to 100 keV, by which the solar wind transfers mass, momentum and energy to the magnetosphere, are discussed. Particular attention is given to the transport processes occurring through the plasma sheet boundary layer and magnetospheric boundary layer, magnetic field line reconnection at neutral lines as a model for magnetospheric substorms, the solar-wind magnetosphere coupling function and interactions of magnetosheath plasma with ambient magnetospheric plasma in the magnetospheric boundary layer. The hot plasmas in the plasma source regions are noted to have higher densities and lower temperatures than those in the storage regions, while those in the transport regions have intermediate densities and temperatures and often exhibit anisotropies and gradients, as well as enhanced electrostatic wave emission and electric currents. The importance of the outer magnetosphere for studies in collisionless plasma physics is emphasized.

Eastman, T. E.; Frank, L. A.

287

Plasma turbulence calculations on supercomputers  

SciTech Connect

To predict the size, expense, and performance of magnetic fusion reactors, it is critical to know the scaling of particle transport and losses across the magnetic field with machine and plasma parameters. The mechanism for transport in magnetically confined plasmas is not yet known. However, at the plasma edge, losses larger than those predicted by classical theory have been shown to be induced by fluctuations. Numerical calculations of plasma turbulence are expected to lead to the identification of the transport scaling parameters. This paper discusses how the fluid approach to plasma dynamics makes tractable some plasma turbulence problems for which kinetic theory calculations are, at present, too complex. Only with present supercomputers can this problem be treated for the edge plasma.

Carreras, B.A.; Dominquez, N.; Drake, J.B.; Leboeuf, J.N. (Oak Ridge National Lab., Oak Ridge, TN (US)); Charlton, L.A.; Holmes, J.A.; Lee, D.K.; Lynch, V.E. (Computing and Telecommunications Div., Martin Marietta Energy Systems, Inc., Oak Ridge, TN (US)); Garcia, L. (Univ. Complutense and Association CIEMAT-EURATOM, Madrid (ES))

1990-01-01

288

Plasma Calcitonin in Renal Osteodystrophy  

PubMed Central

Whether calcitonin plays a significant role in the pathogenesis of renal osteodystrophy is not known. Plasma calcitonin-like activity (CLA) was measured by means of an extraction procedure and bioassay in 17 patients with chronic renal failure. Recent bone biopsy data were available for 11 patients. Plasma CLA was found to be in the normal range in the patients studied. There was a positive and strong correlation between plasma calcium and plasma CLA. Chronic dialysis and renal transplantation had no significant effect on plasma CLA. The severity and type of bone lesions did not correlate with plasma CLA. Although plasma calcitonin in chronic renal failure does not appear to be directly related to renal osteodystrophy, normal mobilization of calcitonin may protect the skeleton to some degree from the high levels of parathyroid hormone usually present in such patients.

Chittal, S. M.; Oreopoulos, D. G.; deVeber, G. A.; Thomas, P.; Rabinovich, S.; Lloyd, G. J.; Kumar, M. A.; Rapoport, A.

1971-01-01

289

Generator powered plasma focus  

SciTech Connect

An earlier set of experiments will be described briefly, in which plate flux compression generators were used to power a Plasma Focus. Currents, voltages and 'rundown times' obtained in these experiments are shown to agree well with a simple model. This same model is then used to show how dramatic operational improvements could be obtained with use of an appropriate fuse, provided the model remained valid.

Fowler, C. M.

2002-01-01

290

Electrons, Ions and Plasma  

NSDL National Science Digital Library

This explanation of the factors that produce the polar aurora, (northern lights) discusses the role of electrons in the ionosphere, positive ions in the solar wind, and the mixing of the two to create plasma. The work of Kristian Birkeland of Norway in exploring the cause of the aurora is cited and a link leads to in-depth information on auroras, including some dramatic photographs.

Stern, David

291

Electrons, Ions and Plasmas  

NSDL National Science Digital Library

This series of web pages provides information on a range of topics regarding charged particles. Starting with the properties of atomic electrons, this material describes the Edison and photoelectric effects, the interaction between charged particles and magnetic fields, and the creation of plasmas and positive ions. Other topics, including the history of research on charges, are covered in linked pages. This is part of a series of non-mathematical, linked explorations of the Earth's Magnetosphere.

Peredo, Mauricio; Mendez, J.; Stern, David P. (David Peter), 1931-

2009-04-15

292

On neutral plasma oscillations  

SciTech Connect

We examine the conditions for the existence of spectrally stable neutral modes in a Vlasov-Poisson plasma and show that for stable equilibria of systems that have unbounded spatial domain, the only possible neutral modes are those with phase velocities that correspond to stationary inflection points of the equilibrium distribution function. It is seen that these neutral modes can possess positive or negative free energy.

Shadwick, B.A.; Morrison, P.J.

1993-06-01

293

Beam-Plasma Interactions  

SciTech Connect

We describe the theory of a cyclotron maser instability which appears to be a likely source of auroral kilometric radiation and its generation in a laboratory experiment. We then outline plans for future development of the experiment to investigate a wider range of instabilities resulting from the existence of electron beams in a plasma. The basic theory theory underlying a few of these is then discussed.

Cairns, R. A.; Vorgul, I. [School of Mathematics and Statistics, University of St Andrews, St Andrews, Fife, KY16 9SS UK (United Kingdom); Bingham, R. [SUPA Department of Physics, University of Strathclyde, Glasgow, G4 0NG (United Kingdom); Rutherford Appleton Laboratory, Chilton, Didcot, Oxon. OX11 0QX (United Kingdom); Ronald, K.; Speirs, D. C.; Phelps, A. D. R.; McConville, S. L.; Gillespie, K. M.; Cross, A. W.; Robertson, C. W.; Whyte, C. G. [SUPA Department of Physics, University of Strathclyde, Glasgow, G4 0NG (United Kingdom); Kellett, B. J. [Rutherford Appleton Laboratory, Chilton, Didcot, Oxon. OX11 0QX (United Kingdom)

2009-11-10

294

Screening Resonances In Plasmas  

SciTech Connect

When it was suggested that a new recombination mechanism (Resonant Radiative Recombination (RRR)) which, based on very general physical arguments, should happen in dense plasmas and promises to provide useful information for the local temperature and density diagnostics of plasmas, they assumed the existence of screening resonances. For model potentials the existence of screening resonances has been demonstrated beyond reasonable doubt in a number of calculations. The key question, how well those potentials describe the dominant effects of a real plasma remains open. The relation of theoretical predictions to experimentally measurable effects is an important issue at the present stage of their research. In particular, RRR is expected to account for enhanced recombination rates of low energetic electrons with their ions, since the first stage is the resonant capture of a slow electron by an atom or ion. The mechanism that traps an electron is a combination of complicated many-body interactions of the ions and electrons. For clarity they start here, however, with a discussion in terms of local potential traps the shapes of which are determined predominantly and in an average way by two factors: the degree of screening present at the ionic site and the degree of short-range order in the immediate neighborhood of this ion.

Winkler, P.

1998-12-01

295

A nanoparticle in plasma  

SciTech Connect

Charge and energy fluxes onto a nanoparticle under conditions typical of laboratory plasmas are investigated theoretically. Here, by a nanoparticle is meant a grain the size of which is much smaller than both the electron Larmor radius and Debye length and the thermionic emission from which is not limited by the space charge. Under conditions at which thermionic emission plays an important role, the electric potential and temperature T{sub p} of a nanoparticle are determined by solving a self-consistent set of equations describing the balance of energy and charge fluxes onto the nanoparticle. It is shown that, when the degree of plasma ionization exceeds a critical level, the potential of the nanoparticle and the energy flux onto it increase with increasing nanoparticle temperature, so that, starting from a certain temperature, the nanoparticle potential becomes positive. The critical degree of ionization starting from which the potential of a nanoparticle is always positive is determined as a function of the plasma density and electron temperature. The nanoparticle temperature T{sub p} corresponding to the equilibrium state of a positively charged nanoparticle is found as a function of the electron density for different electron temperatures.

Martynenko, Yu. V.; Nagel', M. Yu.; Orlov, M. A. [Russian Research Centre Kurchatov Institute (Russian Federation)

2009-06-15

296

Plasma Redshift of Photons  

NASA Astrophysics Data System (ADS)

Plasma redshift of photons in extended, hot, sparse plasma is given by ln ( 1+z )=3.326\\cdot 10-25\\cdot int_0^R N_e\\cdot dx., provided that the wavelength ? <= ? _cut-off? 7.12\\cdot 10-6\\cdot ? N_e/T cm, where Ne is the electron density in cm-3, T in ^0K, and R the distance in cm to the emitter. The theory is based on an overlooked interaction of photons with hot sparse electron plasma. It has been overlooked, because the conditions (high temperature and low densities over extended dimensions) necessary for its observation cannot be created in laboratory experiments. Its large magnitude when integrated over astronomical dimensions, nevertheless, has profound implications for our understanding of many astrophysical phenomena, including: the solar redshift, solar corona, transition to the corona and the outer limits of the heliosphere, the redshift of white dwarfs and quasars, and the cosmological redshift. A long series of experiments, including the recently discovered dimming of distant super nova, confirm the theory.

Brynjolfsson, Ari

2000-04-01

297

Undamped electrostatic plasma waves  

NASA Astrophysics Data System (ADS)

Dissipationless wave damping is a characteristic feature of plasma dynamics. However, when the equilibrium particle velocity distribution departs from the usual Maxwellian configuration due to the presence of a small plateau, plasma waves with certain frequency and wavenumber can survive against Landau damping: we name these waves ``corner modes'' since a significant contribution to the charge density associated to these oscillations mainly come from the sharp corners at the boundary of the velocity plateau. Here we show that these undamped waves can be obtained in a wide region of the (k; ?R) plane (?R being the real part of the wave frequency and k the wavenumber), away from the well-known ``thumb curve'' for Langmuir waves and EAWs based on the Maxwellian. The effect of altering the tails of the velocity distribution on the thumb curve is also discussed and a rule of thumb is obtained for assessing how the existence of a plateau shifts roots off of the thumb curve. Suggestions are made for interpreting recent experimental observations of electrostatic waves in nonneutral plasmas. Kinetic Vlasov-Poisson simulations are specifically designed to provide support to the analytical predictions.

Valentini, Francesco; Perrone, Denise; Califano, Francesco; Pegoraro, Francesco; Veltri, Pierluigi; Morrison, Philip; O'Neil, Thomas

2012-10-01

298

New Aspects of Plasma Physics  

NASA Astrophysics Data System (ADS)

Nonlinear collective processes in very dense plasmas / P. K. Shukla, B. Eliasson and D. Shaikh -- Quantum, spin and QED effects in plasmas / G. Brodin and M. Marklund -- Spin quantum plasmas - new aspects of collective dynamics / M. Marklund and G. Brodin -- Revised quantum electrodynamics with fundamental applications / B. Lehnert -- Quantum methodologies in beam, fluid and plasma physics / R. Fedele -- Plasma effects in cold atom physics / J. T. Mendonca ... [et al.] -- General properties of the Rayleigh-Taylor instability in different plasma configurations: the plasma foil model / F. Pegoraro and S. V. Bulanov -- The Rayleigh-Taylor instability of a plasma foil accelerated by the radiation pressure of an ultra intense laser pulse / F. Pegoraro and S. V. Bulanov -- Generation of galactic seed magnetic fields / H. Saleem -- Nonlinear dynamics of mirror waves in non-Maxwellian plasmas / O. A. Pokhotelov et al. -- Formation of mirror structures near instability threshold / E. A. Kuznetsov, T. Passot and P. L. Sulem -- Nonlinear dispersive Alfvén waves in magnetoplasmas / P. K. Shukla ... [et al.] -- Properties of drift and Alfvén waves in collisional plasmas / J. Vranjes, S. Poedts and B. P. Pandey -- Current driven acoustic perturbations in partially ionized collisional plasmas / J. Vranjes ... [et al.] -- Multifluid theory of solitons / F. Verheest -- Nonlinear wavepackets in pair-ion and electron-positron-ion plasmas / I. Kourakis et al. -- Electro-acoustic solitary waves in dusty plasmas / A. A. Mamun and P. K. Shukla -- Physics of dust in magnetic fusion devices / Z. Wang et al. -- Short wavelength ballooning mode in Tokamaks / A. Hirose and N. Joiner -- Effects of perpendicular shear superposition and hybrid ions intruduction on parallel shear driven plasma instabilities / T. Kaneko and R. Hatakeyama.

Schukla, Padma K.; Stenflo, Lennart; Eliasson, Bengt

2008-03-01

299

Precise plasma process control based on combinatorial plasma etching  

NASA Astrophysics Data System (ADS)

For the realization of super-fine plasma etching process, fluctuations of plasma parameters such as densities of radicals, ions and electrons is required to be minimized. In particular, conditions of inner surface of reactor wall can significantly influence on the radical density in subsequent plasma process owing to outgas consisting of deposited reaction products and adsorbed species from the previous process on the wall. To investigate variety of gaseous radical densities for H2/N2 plasma when inner wall condition was changed by the previous process, we analyzed the radical densities using vacuum ultraviolet absorption spectroscopy (VUVAS). It was clearly confirmed that the radical densities in 100-MHz capacitively coupled plasma (CCP) of H2/N2 were temporally changed subsequently after different kind of conditions for H2/N2 plasma, O2 plasma, and air exposure. We clarified how and what kind of etched products or process gases adsorbed on inner wall surface during the previous process and what species desorbed from the wall into bulk plasmas. Then we are trying to establish a precise process control systematically based on the plasma nano-science database that is constructing using the combinatorial plasma etching approach [1]. [4pt] [1] C. Moon, et al., Applied Physics Express 2 (2009) 096001.

Sekine, Makoto; Suzuki, Toshiya; Takeda, Keigo; Kondo, Hiroki; Ishikawa, Kenji; Setsuhara, Yuichi; Shiratani, Masaharu; Hori, Masaru

2012-10-01

300

Plasma Properties of Microwave Produced Plasma in a Toroidal Device  

NASA Astrophysics Data System (ADS)

We have modified a small tokamak, STOR-1M, on loan from University of Saskatchewan, to operate as a low-temperature (˜5 eV) toroidal plasma machine with externally induced toroidal magnetic fields ranging from zero to ˜50 G. The plasma is produced using microwave discharges at relatively high pressures. Microwaves are produced by a kitchen microwave-oven magnetron operating at 2.45 GHz in continuous operating mode, resulting in pulses ˜0.5 s in duration. Initial measurements of plasma formation in this device with and without applied magnetic fields are presented. Plasma density and temperature profiles have been measured using Langmuir probes and the magnetic field profile inside the plasma has been obtained using Hall probes. When the discharge is created with no applied toroidal magnetic field, the plasma does not fill the entire torus due to high background pressure. However, when a toroidal magnetic field is applied, the plasma flows along the applied field, filling the torus. Increasing the applied magnetic field seems to aid plasma formation - the peak density increases and the density gradient becomes steeper. Above a threshold magnetic field, the plasma develops low-frequency density oscillations due to probable excitation of flute modes in the plasma.

Singh, Ajay; Edwards, W. F.; Held, Eric

2011-11-01

301

Gravitational lensing in plasma: Relativistic images at homogeneous plasma  

NASA Astrophysics Data System (ADS)

We investigate the influence of plasma presence on relativistic images formed by Schwarzschild black hole lensing. When a gravitating body is surrounded by a plasma, the lensing angle depends on a frequency of the electromagnetic wave due to refraction properties, and the dispersion properties of the light propagation in gravitational field in plasma. The last effect leads to a difference, even in uniform plasma, of the gravitational deflection angle in plasma from the vacuum case. This angle depends on the photon frequency, which resembles the properties of the refractive prism spectrometer. Here we consider the case of a strong deflection angle for the light, traveling near the Schwarzschild black hole, surrounded by a uniform plasma. Asymptotic formulas are obtained for the case of a very large deflection angle, exceeding 2?. We apply these formulas for calculation of position and magnification of relativistic images in a homogeneous plasma, which are formed by the photons performing one or several revolutions around the central object. We conclude that the presence of the uniform plasma increases the angular size of relativistic rings or the angular separation of point images from the gravitating center. The presence of the uniform plasma increases also a magnification of relativistic images. The angular separation and the magnification become significantly larger than in the vacuum case, when the photon frequency goes to a plasma frequency.

Tsupko, Oleg Yu.; Bisnovatyi-Kogan, Gennady S.

2013-06-01

302

Momentum transfer to rotating magnetized plasma from gun plasma injection  

SciTech Connect

Numerical simulations are carried out to investigate the penetration and momentum coupling of a gun-injected plasma slug into a rotating magnetized plasma. An experiment along these lines is envisioned for the Maryland Centrifugal Experiment (MCX) [R. F. Ellis et al., Phys. Plasmas 8, 2057 (2001)] using a coaxial plasma accelerator gun developed by HyperV Technologies Corp. [F. D. Witherspoon et al., Bull. Am. Phys. Soc. 50, LP1 87 (2005)]. The plasma gun would be located in the axial midplane and fired off-axis into the rotating MCX plasma annulus. The numerical simulation is set up so that the initial momentum in the injected plasma slug is of the order of the initial momentum of the target plasma. Several numerical firings are done into the cylindrical rotating plasma. Axial symmetry is assumed. The slug is seen to penetrate readily and deform into a mushroom, characteristic of interchange deformations. It is found that up to 25% of the momentum in the slug can be transferred to the background plasma in one pass across a cylindrical chord. For the same initial momentum, a high-speed low density slug gives more momentum transfer than a low-speed high density slug. Details of the numerical simulations and a scaling study are presented.

Shamim, Imran; Hassam, A. B.; Ellis, R. F.; Witherspoon, F. D.; Phillips, M. W. [Institute for Research in Electronics and Applied Physics (IREAP), University of Maryland, College Park, Maryland 20742 (United States); HyperV Technologies Corporation, Chantilly, Virginia 20151 (United States)

2006-11-15

303

Lithium plasma emitter for collisionless magnetized plasma experiment  

NASA Astrophysics Data System (ADS)

This paper presents a newly developed lithium plasma emitter, which can provide quiescent and low-temperature collisionless conditions for magnetized plasma experiments. This plasma emitter generates thermal emissions of lithium ions and electrons to produce a lithium plasma. Lithium type beta-eucryptite and lanthanum-hexaboride (LaB6) powders were mixed and directly heated with a tungsten heater to synthesize ion and electron emissions. As a result, a plasma with a diameter of ~15 cm was obtained in a magnetic mirror configuration. The typical range of electron density was 1012-1013 m-3 and that of electron temperature was 0.1-0.8 eV with the emitter operation temperature of about 1500 K. The amplitude fluctuations for the plasma density were lower than 1%.

Kawamori, Eiichirou; Lee, Jyun-Yi; Huang, Yi-Jue; Syugu, Wun-Jheng; Song, Sung-Xuang; Hsieh, Tung-Yuan; Cheng, C. Z.

2011-09-01

304

Lithium plasma emitter for collisionless magnetized plasma experiment  

SciTech Connect

This paper presents a newly developed lithium plasma emitter, which can provide quiescent and low-temperature collisionless conditions for magnetized plasma experiments. This plasma emitter generates thermal emissions of lithium ions and electrons to produce a lithium plasma. Lithium type beta-eucryptite and lanthanum-hexaboride (LaB{sub 6}) powders were mixed and directly heated with a tungsten heater to synthesize ion and electron emissions. As a result, a plasma with a diameter of {approx}15 cm was obtained in a magnetic mirror configuration. The typical range of electron density was 10{sup 12}-10{sup 13} m{sup -3} and that of electron temperature was 0.1-0.8 eV with the emitter operation temperature of about 1500 K. The amplitude fluctuations for the plasma density were lower than 1%.

Kawamori, Eiichirou; Huang, Yi-Jue; Song, Sung-Xuang; Hsieh, Tung-Yuan [Institute of Space, Astrophysical and Plasma Sciences, National Cheng Kung University, Tainan, Taiwan (China); Lee, Jyun-Yi; Syugu, Wun-Jheng [Department of Physics, National Cheng Kung University, Tainan, Taiwan (China); Cheng, C. Z. [Plasma and Space Science Center, National Cheng Kung University, Tainan, Taiwan (China)

2011-09-15

305

Influence of Plasma Instabilities in Ceramic Suspension Plasma Spraying  

NASA Astrophysics Data System (ADS)

Direct current Suspension Plasma Spraying (SPS) allows depositing finely structured coatings. This article presents an analysis of the influence of plasma instabilities on the yttria-stabilized suspension drops fragmentation. A particular attention is paid to the treatment of suspension jet or drops according to the importance of voltage fluctuations (linked to those of the arc root) and depending on the different spray parameters such as the plasma forming gas mixture composition and mass flow rate and the suspension momentum. By observing the suspension drops injection with a fast shutter camera and a laser flash sheet triggered by a defined transient voltage level of the plasma torch, the influence of plasma fluctuations on jet or drops fragmentation is studied through the deviation and dispersion trajectories of droplets within the plasma jet.

Etchart-Salas, R.; Rat, V.; Coudert, J. F.; Fauchais, P.; Caron, N.; Wittman, K.; Alexandre, S.

2007-12-01

306

Plasma generating apparatus for large area plasma processing  

DOEpatents

A plasma generating apparatus for plasma processing applications is based on a permanent magnet line-cusp plasma confinement chamber coupled to a compact single-coil microwave waveguide launcher. The device creates an electron cyclotron resonance (ECR) plasma in the launcher and a second ECR plasma is created in the line cusps due to a 0.0875 tesla magnetic field in that region. Additional special magnetic field configuring reduces the magnetic field at the substrate to below 0.001 tesla. The resulting plasma source is capable of producing large-area (20-cm diam), highly uniform (.+-.5%) ion beams with current densities above 5 mA/cm.sup.2. The source has been used to etch photoresist on 5-inch diam silicon wafers with good uniformity.

Tsai, Chin-Chi (Oak Ridge, TN); Gorbatkin, Steven M. (Oak Ridge, TN); Berry, Lee A. (Oak Ridge, TN)

1991-01-01

307

Plasma cell development and survival.  

PubMed

Plasma cells have long been recognized as the basis of humoral immunity, yet we are only now beginning to appreciate the complexities of plasma cell development and the fact that not all plasma cells are created equal. In vivo, plasma cells can arise from two developmental routes: one occurring outside the follicle and another within the germinal center. A B cell's decision to follow one of these pathways is in part determined by the phenotypic subset to which it belongs and is also influenced by the nature of the antigen eliciting the response and the affinity of the B-cell receptor for that antigen. Once a plasma cell has chosen one of these pathways, the outcome of differentiation is relatively hard-wired. However, the phenotype of the plasma cells arising from these two pathways is distinct in terms of survival, location, and the quantity and quality of antibody they secrete. The extra-follicular pathway represents a relatively unchecked route to differentiation resulting in the generation of short-lived plasma cells that secrete low-affinity antibody. The germinal center response, however, allows the integration of external signals to delay plasma cell differentiation, eventually generating a plasma cell that secretes high-affinity antibody of an appropriate class, and that persists for a lifetime. The means by which these varying properties are conferred to a developing plasma cell are the subject of intense investigation. PMID:20727034

Oracki, Sarah A; Walker, Jennifer A; Hibbs, Margaret L; Corcoran, Lynn M; Tarlinton, David M

2010-09-01

308

Rydberg atoms in ultracold plasmas  

NASA Astrophysics Data System (ADS)

Ultracold plasmas are formed through the photoionization of laser-cooled atoms, or spontaneous ionization of a dense cloud of Rydberg atoms or now molecules[1]. Ultracold plasmas are inherently metastable, as the ions and electrons would be in a lower energy state bound together as atoms. The dominant process of atom formation in these plasmas is three-body recombination, a collision between two electrons and an ion that leads to the formation of a Rydberg atom. This collisional process is not only important in determining the lifetime and density of the plasma, but is also critical in determining the time evolution of the temperature. The formation of the Rydberg atoms is accompanied by an increase in electron energy for the extra electron in the collision, and is a source of heating in these plasmas. Classical three-body recombination theory scales as T-9/2, and thus as a plasma cools due to a process such as adiabatic expansion, recombination-induced heating turns on, limiting the temperature [2]. The Rydberg atoms formed live in the plasma and contribute to the temperature dynamics, as collisions with plasma electrons can change the principal quantum number of the Rydberg atom, driving it to more tightly bound states (a source of plasma heating) or to higher states (a source of plasma cooling). If the plasma is cold and dense enough to be strongly coupled, classical three-body recombination theory breaks down. Recent theoretical work [3] suggests that the rate limits as the plasma gets strongly coupled. I will review the role of Rydberg atoms in ultracold plasmas and prospects for probing Rydberg collisions in the strongly coupled environment. [4pt] [1] J. P. Morrison, et al., Phys. Rev. Lett. 101, 205005 (2008 [0pt] [2] R. S. Fletcher, X. Zhang, and S. L. Rolston, Phys. Rev. Lett. 99, 145001 (2007 [0pt] [3] T. Pohl, private communication.

Rolston, Steven

2009-05-01

309

Production of homogeneous plasmas for laser-plasma interaction experiments  

NASA Astrophysics Data System (ADS)

The plasma is created either by impact on solid targets, or by explosion of a thin polystyrene film using a neodymium laser. In the case of the thin film the plasma has an electronic density profile more or less parabolic in the laser axis sense and uniform in the perpendicular sense. A Mach Zehnder interferometer allowed optimization of the beam focusing conditions, as well as the targets. The resulting plasmas have the required uniformity.

Labaune, Christine; Amiranoff, Francois; Matthieussent, Gilles; Rousseaux, Christophe; Paire, Jean-Baptiste; Verdiell, Jean-Marc; Zeitoun, P.

1988-06-01

310

Metal plasma jet passage through plasma-optical transport system  

Microsoft Academic Search

The passage of a plasma jet of steady-state vacuum arc discharge through a plasma-optical transport (POT) system based on\\u000a a curvilinear magnetic field has been studied. Special features of the system are the absence of a metallic duct and the misfit\\u000a of axes of the guiding magnetic field and the plasma jet. It is demonstrated that the position and shape

V. L. Paperny; V. I. Krasov

2011-01-01

311

Towards Plasma Surgery: Plasma Treatment of Living Cells  

NASA Astrophysics Data System (ADS)

The physical, biological and technical background for high-precision plasma surgery is prepared in a multi-disciplinary team. The aim of the research is to achieve controlled removal of diseased cells and bacteria without harming the healthy rest of the tissue. For this purpose, a small, cold, flexible and non-toxic plasma is developed (the plasma needle) and tested on cultured cells and bacterial samples. The needle is an atmospheric discharge induced by a radio-frequency voltage applied to a metal pin. This plasma operates at room temperature, in the milliwatt power regime; it poses no risk of thermal or electrical damage to living tissues. Several beneficial responses of living cells to plasma treatment have been already identified. Plasma does not cause accidental cell death (necrosis), which leads to inflammation and tissue damage. Instead, it allows to detach cells from each other and from the scaffold, and thus to remove them in a non-destructive way. Moreover, plasma is capable of bacterial inactivation. I parallel, we have determined the electrical and optical properties of the plasma and found a method of precise positioning of the plasma needle with respect to the treated tissue.

Stoffels, E.; Kieft, I. E.; Sladek, R. E. J.; Slaaf, D. W.; van der Laan, E. P.; Jimenez-Moreno, P.; Steinbuch, M.

2004-12-01

312

A contoured gap coaxial plasma gun with injected plasma armature  

SciTech Connect

A new coaxial plasma gun is described. The long term objective is to accelerate 100-200 {mu}g of plasma with density above 10{sup 17} cm{sup -3} to greater than 200 km/s with a Mach number above 10. Such high velocity dense plasma jets have a number of potential fusion applications, including plasma refueling, magnetized target fusion, injection of angular momentum into centrifugally confined mirrors, high energy density plasmas, and others. The approach uses symmetric injection of high density plasma into a coaxial electromagnetic accelerator having an annular gap geometry tailored to prevent formation of the blow-by instability. The injected plasma is generated by numerous (currently 32) radially oriented capillary discharges arranged uniformly around the circumference of the angled annular injection region of the accelerator. Magnetohydrodynamic modeling identified electrode profiles that can achieve the desired plasma jet parameters. The experimental hardware is described along with initial experimental results in which approximately 200 {mu}g has been accelerated to 100 km/s in a half-scale prototype gun. Initial observations of 64 merging injector jets in a planar cylindrical testing array are presented. Density and velocity are presently limited by available peak current and injection sources. Steps to increase both the drive current and the injected plasma mass are described for next generation experiments.

Witherspoon, F. Douglas; Case, Andrew; Messer, Sarah J.; Bomgardner, Richard II; Phillips, Michael W.; Brockington, Samuel; Elton, Raymond [HyperV Technologies Corp., Chantilly, Virginia 20151 (United States)

2009-08-15

313

Whistler wave driven plasma thruster  

SciTech Connect

High density plasma can be generated by electron cyclotron resonance heating (ECRH) using whistler waves at densities for which the plasma frequency is much higher than the cyclotron frequency. This will result in a thruster operating at specific impulses of 10[sup 3]--10[sup 4] s and much higher power and thrust densities than usual for ECRH devices. As the plasma generation is by electromagnetic waves, there are no electrodes, and wall material problems are greatly eased, permitting reliable, long lifetime operation. The authors report on the modeling of such a thruster, including plasma flow as well as losses to an end wall and ionization. A helical antenna to couple the waves into the plasma column is analyzed, including effects of the anisotropic plasma dielectric constant. An initial experiment to test the concept is planned.

Hooper, E.B.; Stallard, B.W.; Makowski, M.A.

1992-10-05

314

Whistler wave driven plasma thruster  

SciTech Connect

High density plasma can be generated by electron cyclotron resonance heating (ECRH) using whistler waves at densities for which the plasma frequency is much higher than the cyclotron frequency. This will result in a thruster operating at specific impulses of 10{sup 3}--10{sup 4} s and much higher power and thrust densities than usual for ECRH devices. As the plasma generation is by electromagnetic waves, there are no electrodes, and wall material problems are greatly eased, permitting reliable, long lifetime operation. The authors report on the modeling of such a thruster, including plasma flow as well as losses to an end wall and ionization. A helical antenna to couple the waves into the plasma column is analyzed, including effects of the anisotropic plasma dielectric constant. An initial experiment to test the concept is planned.

Hooper, E.B.; Stallard, B.W.; Makowski, M.A.

1992-10-05

315

Whistler wave driven plasma thruster  

SciTech Connect

High density plasma can be generated by electron cyclotron resonance heating (ECRH) using whistler waves at densities for which the plasma frequency is much higher than the cyclotron frequency. This will result in a thruster operating at specific impulses of 10[sup 3]--10[sup 4] s and much higher power and thrust densities than usual for ECRH devices. As the plasma generation is by electromagnetic waves, there are no electrodes, and wall material problems are greatly eased, permitting reliable, long lifetime operation. We report on the modeling of such a thruster, including plasma flow as well as losses to an end wall and ionization. A helical antenna to couple the waves into the plasma column is analyzed, including effects of the anisotropic plasma dielectric constant. An initial experiment to test the concept is planned.

Bickford Hooper, E.; Stallard, B.W.; Makowski, M.A. (Lawrence Livermore National Laboratory L-637, P.O. Box 808 Livermore, CA 94550-9900 (United States))

1993-01-20

316

Surface currents on ideal plasmas  

SciTech Connect

The surface (or 'skin') current that can flow at a perturbed interface between plasma and vacuum is considered in the approximation where a surface marks a sharp transition from plasma to vacuum. A short magnetohydrodynamic calculation gives an exact and general expression for the component perpendicular to the average of the magnetic field either side of the surface, finding it proportional to the edge plasma pressure. A consequence is that for all plasmas with zero surface current at equilibrium, the surface current associated with any linear instability will flow parallel to the magnetic field. The surface current is calculated for a simple but realistic model of a cylindrical plasma, and found to depend on the type of instability, and consequently on the particular plasma equilibrium. This is illustrated for two well known cases.

Webster, Anthony J. [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom)

2010-11-15

317

A generalized plasma etching model  

NASA Astrophysics Data System (ADS)

A generalized plasma etching model was developed on the basis of the Zawaideh and Kim (1987) model, which includes the effects of multiion and multineutral gas species. New generalized plasma-transport equations were derived for multiion species, which are valid for collisional to weakly collisional plasma. In addition, a new particle-balance model is introduced, which incorporates the effects of gas composition, gas-flow rate, pumping rate, ion and neutral-gas chemistry, and atomic reactions on the neutral gas and plasma parameters such as densities and pressures of the neutral-gas and plasma species. Predictions obtained for SiO2 plasma etching with CF4 gas agreed well with the results of the measurements of etch rate as functions of neutral gas pressure, CF4 flow rate, and RF power.

Zawaideh, Emad; Kim, N. S.

1988-10-01

318

Resonance microwave volume plasma source  

SciTech Connect

A conceptual design of a microwave gas-discharge plasma source is described. The possibility is considered of creating conditions under which microwave energy in the plasma resonance region would be efficiently converted into the energy of thermal and accelerated (fast) electrons. Results are presented from interferometric and probe measurements of the plasma density in a coaxial microwave plasmatron, as well as the data from probe measurements of the plasma potential and electron temperature. The dynamics of plasma radiation was recorded using a streak camera and a collimated photomultiplier. The experimental results indicate that, at relatively low pressures of the working gas, the nonlinear interaction between the microwave field and the inhomogeneous plasma in the resonance region of the plasmatron substantially affects the parameters of the ionized gas in the reactor volume.

Berezhetskaya, N. K.; Kop'ev, V. A.; Kossyi, I. A.; Malykh, N. I.; Misakyan, M. A.; Taktakishvili, M. I.; Temchin, S. M. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation); Lee, Young Dong [Samsung Advanced Institute of Technology (Korea, Republic of)

2007-07-15

319

Electron cyclotron resonance plasma photos  

SciTech Connect

In order to observe and study systematically the plasma of electron cyclotron resonance (ECR) ion sources (ECRIS) we made a high number of high-resolution visible light plasma photos and movies in the ATOMKI ECRIS Laboratory. This required building the ECR ion source into an open ECR plasma device, temporarily. An 8MP digital camera was used to record photos of plasmas made from Ne, Ar, and Kr gases and from their mixtures. We studied and recorded the effect of ion source setting parameters (gas pressure, gas composition, magnetic field, and microwave power) to the shape, color, and structure of the plasma. The analysis of the photo series gave us many qualitative and numerous valuable physical information on the nature of ECR plasmas.

Racz, R.; Palinkas, J. [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem ter 18/c (Hungary); University of Debrecen, H-4010 Debrecen, Egyetem ter 1 (Hungary); Biri, S. [Institute of Nuclear Research (ATOMKI), H-4026 Debrecen, Bem ter 18/c (Hungary)

2010-02-15

320

Recovering aluminum via plasma processing  

NASA Astrophysics Data System (ADS)

A process based on the use of a plasma system for recovering aluminum from dross, beverage cans, and aluminum scrap has been developed. The plasma process is clean, and there is no need for the addition of any compound, such as salt. In principle, a higher recovery rate of aluminum is attainable, since no oxidation of the aluminum occurs during the process. An economic analysis shows that the operating costs for the plasma system are at least 23% cheaper than for the traditional process using air/gas or ail/oil burners; the plasma process also does not generate either of the common residues produced by the burners. The maintenance costs of the plasma process are also lower than that of the traditional process. Overall, the plasma system is cheaper, cleaner, and easier than the oil/gas burner technology when recovering aluminum from dross, beverage cans, and scrap.

Szente, R. N.; Schroeter, R. A.; Garcia, M. G.; Bender, O. W.

1997-11-01

321

Low energy plasma analyzer  

NASA Astrophysics Data System (ADS)

A low energy plasma analyzer (LEPA) capable of determining the 3D distribution function of electrons and positive ions in the energy range from 10 eV to 30 KeV is described. It simultaneously determines the location in the distribution function and the frequency at which coherent wave-particle interactions may occur. LEPA incorporates a particle correlator that provides a direct method of identifying regions of particle velocity space in which strong, wave-particle interactions occur. The LEPA correlator operates in the frequency range from 0 to 5.0 kHz.

Hardy, David A.; Walton, D. M.; Johnstone, A. D.; Smith, M. F.; Gough, M. P.; Huber, A.; Pantazis, J.; Burkhardt, R.

1993-04-01

322

FPD plasma heating systems  

SciTech Connect

Tandem mirror devices rely on a number of plasma heating systems to create and maintain potential and density profiles which axially confine the central cell and provide MHD stability. The Fusion Power Demonstrator (FPD) tandem mirror study was carried out in three stages, each facility was configured with a slightly different mission and set of constraints. Although the heating system requirements varied in the three stages, the potential peak and thermal barrier ECRH systems and the sloshing ion neutral beam system were common elements of the configurations. The heating systems' requirements, the design approach, and the systems' description are presented.

Freije, S.A.

1985-07-01

323

Laser plasma accelerators  

SciTech Connect

This review article highlights the tremendous evolution of the research on laser plasma accelerators which has, in record time, led to the production of high quality electron beams at the GeV level, using compact laser systems. I will describe the path we followed to explore different injection schemes and I will present the most significant breakthrough which allowed us to generate stable, high peak current and high quality electron beams, with control of the charge, of the relative energy spread and of the electron energy.

Malka, V. [Laboratoire d'Optique Appliquee, ENSTA-ParisTech, CNRS, Ecole Polytechnique, UMR 7639, 91761 Palaiseau (France)

2012-05-15

324

Renormalization and plasma physics  

SciTech Connect

A review is given of modern theories of statistical dynamics as applied to problems in plasma physics. The derivation of consistent renormalized kinetic equations is discussed, first heuristically, later in terms of powerful functional techniques. The equations are illustrated with models of various degrees of idealization, including the exactly soluble stochastic oscillator, a prototype for several important applications. The direct-interaction approximation is described in detail. Applications discussed include test particle diffusion and the justification of quasilinear theory, convective cells, E vector x B vector turbulence, the renormalized dielectric function, phase space granulation, and stochastic magnetic fields.

Krommes, J.A.

1980-02-01

325

Dusty plasma liquids  

NASA Astrophysics Data System (ADS)

Dusty plasma liquids are formed by suspending negatively charged micro-metre sized particles in a low pressure discharge background. They are good candidates for studying the generic spatio-temporal dynamical behaviours at the kinetic level through direct optical video-microscopy due to the sub-mm interparticle spacing and the slow time scale. In this paper, starting from the basic picture of the avalanche type stick slip cooperative hopping process under the interplay of mutual coupling and stochastic thermal agitation, we briefly review our recent study on particle micro-motion and the associated structural rearrangement. The effects of mesoscopic confinement and external slow shear drive are also discussed.

Chan, Chia-Ling; Lai, Ying-Ju; Woon, Wei-Yen; Chu, Hong-Yu; I, Lin

2005-05-01

326

Progress on laser plasma accelerators  

SciTech Connect

Several laser plasma accelerator schemes are reviewed, with emphasis on the Plasma Beat Wave Accelerator (PBWA). Theory indicates that a very high acceleration gradient, of order 1 GeV/m, can exist in the plasma wave driven by the beating lasers. Experimental results obtained on the PBWA experiment at UCLA confirms this. Parameters related to the PBWA as an accelerator system are derived, among them issues concerning the efficiency and the laser power and energy requirements are discussed.

Chen, P.

1986-04-01

327

Plasma characterization of dry ?-EDM  

Microsoft Academic Search

An attempt was made to characterize the dry microelectric discharge machining (?-EDM) plasma systematically by using optical\\u000a emission spectroscopy. In order to characterize the plasma and its parameters such as plasma temperature, electron density,\\u000a Debye length, and gamma parameter, the optical spectra were recorded for different energies and with different diameters of\\u000a tool electrode. From the recorded spectra, using line

S. Kanmani Subbu; G. Karthikeyan; J. Ramkumar; S. Dhamodaran

2011-01-01

328

Atmospheric-pressure plasma jet  

Microsoft Academic Search

Atmospheric-pressure plasma jet. A .gamma.-mode, resonant-cavity plasma discharge that can be operated at atmospheric pressure and near room temperature using 13.56 MHz rf power is described. Unlike plasma torches, the discharge produces a gas-phase effluent no hotter than 250.degree. C. at an applied power of about 300 W, and shows distinct non-thermal characteristics. In the simplest design, two concentric cylindrical

Selwyn; Gary S

1999-01-01

329

The plasma environment of comets  

SciTech Connect

U.S. research activities in the area of cometary plasma physics during 1987-1990 are reviewed. Consideration is given to mass loading and its consequences in the upstream region, the cometary shock, the cometosheath, the diamagnetic cavity boundary and the inner shock, and the plasma tail. Special attention is given to models and observations that have modified the pre-encounter understanding of cometary plasma environments. 211 refs.

Gombosi, T.I. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

330

Parallel plasma fluid turbulence calculations  

Microsoft Academic Search

The study of plasma turbulence and transport is a complex problem of critical importance for fusion-relevant plasmas. To this day, the fluid treatment of plasma dynamics is the best approach to realistic physics at the high resolution required for certain experimentally relevant calculations. Core and edge turbulence in a magnetic fusion device have been modeled using state-of-the-art, nonlinear, three-dimensional, initial-value

J. N. Leboeuf; B. A. Carreras; L. A. Charlton; J. B. Drake; V. E. Lynch; D. E. Newman; K. L. Sidikman; D. A. Spong

1994-01-01

331

PHOTOIONIZATIONAL PLASMAS. II. COMPUTATIONAL RESULTS  

SciTech Connect

A new computer code, PhiCRE, has been developed to calculate the ionization and population distributions in a photoionizational-collisional-radiative plasma. Comparisons with experiments show that the present code provides rather accurate ionization distributions in photoionized plasmas and show reasonable agreement with other codes. Using this code, we have carried out a systematic study of the behavior of the charge state distributions and the average charge as a function of several parameters of the incident radiation and the plasma parameters.

Wang Feilu; Salzmann, David; Zha, Gang [Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Takabe, Hideaki, E-mail: wfl@bao.ac.cn [Institute for Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan)

2011-11-20

332

Modelling and experimental analysis of vacuum plasma spraying. Part I: prediction of initial plasma properties at plasma gun exit  

Microsoft Academic Search

The plasma energy input rate of a dc Ar + H2 plasma jet has been measured experimentally under a series of vacuum plasma spraying (VPS) processing conditions. The plasma energy input rate increased approximately linearly with increasing plasma current and Ar flow rate, increased approximately parabolically with increasing H2 flow rate, but did not vary measurably with changes in VPS

Y. Y. Zhao; P. S. Grant; B. Cantor

2000-01-01

333

Issues in tokamak\\/stellarator transport and confinement enhancement mechanisms  

Microsoft Academic Search

At present, the mechanism for anomalous energy transport in low- toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E × B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish

Perkins

1990-01-01

334

Influence of anomalous thermal losses of ignition conditions  

SciTech Connect

In the process of achieving ignition conditions, it is likely that microinstabilities, which lead to anomalous thermal transport of the fusing nuclei, will be present. When such phenomena are taken into account, an appropriate formulation of ignition criteria becomes necessary. In particular, a new type of plasma density limit is identified.

Coppi, B.; Tang, W.M.

1986-05-01

335

Modeling of magnetron sputtering plasmas  

NASA Astrophysics Data System (ADS)

Partially ionized, low-temperature plasmas have been used extensively in many areas of technology. These applications of plasma include surface processing and lighting devices. There are three major categories in surface processing: sputtering, etching and surface modification. The examples of lighting device application are light bulbs, lasers and plasma display devices. In this discussion, simulation study of magnetron sputtering system are reviewed and future issues of these systems are discussed. A two-dimensional three-velocity particle-in-cell (PIC) code is used to simulate kinetic plasma properties in a planar magnetron system with realistic magnetic fields in two and three dimensions. Various plasma characteristics and erosion profiles of a target material are obtained with these magnetic fields. Scaling formulas are used in order to estimate the steady-state properties of plasma and reduce computation time. Variations in the geometry and the magnetic field optimize these erosion profiles and plasma characteristics. For the plasma characteristics, we also calculate the plasma temperature and the velocity distribution function. The velocity distribution function of electrons is nearly Maxwellian, while that of ions is non-Maxwellian. The electron temperature in the bulk coincides well with the experimentally measured values. The majority of ions are in the energy range below half of the applied voltage.

Shon, C. H.; Lee, J. K.

2002-05-01

336

Autoresonant Excitation of Antiproton Plasmas  

SciTech Connect

We demonstrate controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense, and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination.

Andresen, G. B.; Bowe, P. D.; Hangst, J. S. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Ashkezari, M. D.; Hayden, M. E. [Department of Physics, Simon Fraser University, Burnaby British Columbia, V5A 1S6 (Canada); Baquero-Ruiz, M.; Chapman, S.; Fajans, J.; Povilus, A.; So, C. [Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 (United States); Bertsche, W.; Butler, E.; Charlton, M.; Humphries, A. J.; Madsen, N.; Werf, D. P. van der [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); Carpenter, P. T.; Hurt, J. L.; Robicheaux, F. [Department of Physics, Auburn University, Auburn, Alabama 36849-5311 (United States); Cesar, C. L. [Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-972 (Brazil)

2011-01-14

337

Method for generating surface plasma  

DOEpatents

A method for generating a discharge plasma which covers a surface of a body in a gas at pressures from 0.01 Torr to atmospheric pressure, by applying a radio frequency power with frequencies between approximately 1 MHz and 10 GHz across a plurality of paired insulated conductors on the surface. At these frequencies, an arc-less, non-filamentary plasma can be generated to affect the drag characteristics of vehicles moving through the gas. The plasma can also be used as a source in plasma reactors for chemical reaction operations.

Miller, Paul A. (Albuquerque, NM); Aragon, Ben P. (Albuquerque, NM)

2003-05-27

338

Electrical characterization of rf plasmas  

SciTech Connect

Radio-frequency (rf) electrical sources are commonly used to generate plasmas for processing of industrial materials and for related experimental work. Published descriptions of such plasmas usually include generator-power measurements, and occasionally include plasma dc-bias measurements. One or both of these quantitites are also used in industrial feedback ccontrol systems for setpoint regulation. Recent work at Sandia an elsewhere with an experimental rf discharge device (the GEC RF Reference Cell'') has shown that power and dc-bias levels are often insufficient information for specifying the state of the plasma. The plasma can have nonlinear electrical characteristics that cause harmonic generation, and the harmonic levels can depend sensitively on the impedance of the external circuitry at harmonic frequencies. Even though the harmonics may be low in amplitude, they can be directly related to large changes in plasma power and to changes in optical emission from the plasma. Consequently, in order for a worker to truly master the plasma-generation process, it is necessary to understand, measure, and control electrical characteristics of the plamsa. In this paper we describe technique that have been developed from work with the Reference Cell for making electrical measurements on rf plasmas, and we describe surprising observations of harmonic behavior. 10 refs., 4 figs.

Miller, P.A.

1991-08-01

339

Quarantine Plasma: Quo vadis?  

PubMed Central

Summary Upon the introduction of mandatory nucleic acid amplification technology (NAT) testing in Germany for HCV, quarantining of fresh frozen plasma (FFP) was reduced in 2002 from 6 to 4 months. In 2004 HIV-1 NAT and in 2005 anti-HBc testing were introduced to further reduce the residual transmission risks for transfusion relevant viruses. After testing more than 40 million donations by HCV NAT it became obvious that NAT testing has a very significant impact on viral blood safety by reducing the residual risk by a factor of 10. Only one documented HCV transmission occurred during more than 10 years of NAT testing in Germany, indicating that the remaining risk is marginal. Similar data were obtained for HIV-1. The question arises whether we could discontinue quarantining of FFP or further reduce the quarantining interval for retesting of the donor. This could facilitate logistics and reduce losses as quarantine FFP can be released earlier after donation and at regular donation intervals. Essential parameters for estimating the remaining infectious risks are the minimal infectious dose and replication kinetics of the viruses involved, the detection limits of the NAT tests applied, and the volume of plasma transfused. In essence it can be assumed that discontinuation of quarantining would only marginally increase the residual risk and that the reduction of the quarantine period to only 4 weeks would add an additional benefit to the viral safety of quarantine FFP.

Roth, W. Kurt

2010-01-01

340

Plasma Redshift Cosmology  

NASA Astrophysics Data System (ADS)

The newly discovered plasma redshift cross section explains a long range of phenomena; including the cosmological redshift, and the intrinsic redshift of Sun, stars, galaxies and quasars. It explains the beautiful black body spectrum of the CMB, and it predicts correctly: a) the observed XRB, b) the magnitude redshift relation for supernovae, and c) the surface- brightness-redshift relation for galaxies. There is no need for Big Bang, Inflation, Dark Energy, Dark Matter, Accelerated Expansion, and Black Holes. The universe is quasi-static and can renew itself forever (for details, see: http://www.plasmaredshift.org). There is no cosmic time dilation. In intergalactic space, the average electron temperature is T = 2.7 million K, and the average electron density is N = 0.0002 per cubic cm. Plasma redshift is derived theoretically from conventional axioms of physics by using more accurate methods than those conventionally used. The main difference is: 1) the proper inclusion of the dielectric constant, 2) more exact calculations of imaginary part of the dielectric constant, and as required 3) a quantum mechanical treatment of the interactions.

Brynjolfsson, Ari

2011-04-01

341

Undamped electrostatic plasma waves  

SciTech Connect

Electrostatic waves in a collision-free unmagnetized plasma of electrons with fixed ions are investigated for electron equilibrium velocity distribution functions that deviate slightly from Maxwellian. Of interest are undamped waves that are the small amplitude limit of nonlinear excitations, such as electron acoustic waves (EAWs). A deviation consisting of a small plateau, a region with zero velocity derivative over a width that is a very small fraction of the electron thermal speed, is shown to give rise to new undamped modes, which here are named corner modes. The presence of the plateau turns off Landau damping and allows oscillations with phase speeds within the plateau. These undamped waves are obtained in a wide region of the (k,{omega}{sub R}) plane ({omega}{sub R} being the real part of the wave frequency and k the wavenumber), away from the well-known 'thumb curve' for Langmuir waves and EAWs based on the Maxwellian. Results of nonlinear Vlasov-Poisson simulations that corroborate the existence of these modes are described. It is also shown that deviations caused by fattening the tail of the distribution shift roots off of the thumb curve toward lower k-values and chopping the tail shifts them toward higher k-values. In addition, a rule of thumb is obtained for assessing how the existence of a plateau shifts roots off of the thumb curve. Suggestions are made for interpreting experimental observations of electrostatic waves, such as recent ones in nonneutral plasmas.

Valentini, F.; Perrone, D.; Veltri, P. [Dipartimento di Fisica and CNISM, Universita della Calabria, 87036 Rende (CS) (Italy); Califano, F.; Pegoraro, F. [Dipartimento di Fisica and CNISM, Universita di Pisa, 56127 Pisa (Italy); Morrison, P. J. [Institute for Fusion Studies and Department of Physics, University of Texas at Austin, Austin, Texas 78712-1060 (United States); O'Neil, T. M. [Department of Physics, University of California at San Diego, La Jolla, California 92093 (United States)

2012-09-15

342

Proton radiography in plasma  

NASA Astrophysics Data System (ADS)

Generation of high intensity and well collimated multi-energetic proton beams from laser-matter interaction extends the possibility to use protons as a diagnostic tool to image imploding target in Inertial Confinement Fusion (ICF) experiments. Due to the very large mass densities reached during implosion, protons traveling through the target undergo a very large number of collisions. Therefore the analysis of experimentally obtained proton images requires care and accurate numerical simulations using both hydrodynamic and Monte Carlo codes. The impact of multiple scattering needs to be carefully considered by taking into account the exact stopping power for dense matter and for the underdense plasma corona. In our paper, density, temperature and ionization degree profiles of the imploding target are obtained by 2D hydrodynamic simulations performed using CHIC code. Proton radiography images are simulated using the Monte Carlo code (MCNPX; adapted to correctly describe multiple scattering and plasma stopping power) in order to reconstruct the complete hydrodynamic history of the imploding target. Finally we develop a simple analytical model to study the performance of proton radiography as a function of initial experimental parameters, and identify two different regimes for proton radiography in ICF.

Volpe, L.; Batani, D.; Morace, A.; Nicolai, Ph.; Regan, C.; Ravasio, A.

2011-10-01

343

Periodically oscillating plasma sphere  

SciTech Connect

The periodically oscillating plasma sphere, or POPS, is a novel fusion concept first proposed by D. C. Barnes and R. A. Nebel [Fusion Technol. 38, 28 (1998)]. POPS utilizes the self-similar collapse of an oscillating ion cloud in a spherical harmonic oscillator potential well formed by electron injection. Once the ions have been phase-locked, their coherent motion simultaneously produces very high densities and temperatures during the collapse phase of the oscillation. A requirement for POPS is that the electron injection produces a stable harmonic oscillator potential. This has been demonstrated in a gridded inertial electrostatic confinement device and verified by particle simulation. Also, the POPS oscillation has been confirmed experimentally through observation that the ions in the potential well exhibit resonance behavior when driven at the POPS frequency. Excellent agreement between the observed POPS frequencies and the theoretical predictions has been observed for a wide range of potential well depths and three different ion species. Practical applications of POPS require large plasma compressions. These large compressions have been observed in particle simulations, although space charge neutralization remains a major issue.

Park, J.; Nebel, R.A.; Stange, S.; Murali, S. Krupakar [Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States); University of Wisconsin, Madison, Wisconsin 53706 (United States)

2005-05-15

344

Plasma networking in magnetically confined plasmas and diagnostics of nonlocal heat transport in tokamak filamentary plasmas  

NASA Astrophysics Data System (ADS)

The method of multilevel dynamical contrasting is applied to analyzing available data from tokamak plasmas. The results illustrate a possibility of extending the concept of the plasma percolating networks in dense Z pinches (and other inertially confined plasmas) to the case of magnetically confined plasmas. This extension suggests a necessity to append the conventional picture of the nonfilamentary plasma (which is nearly a fluid described by conventional magnetohydrodynamics) with a ``network'' component which is formed by the strongest long-living filaments of electric current and penetrate the ``fluid'' component. Signs of networking are found in visible light and soft x-ray images, and magnetic probing data. A diagnostic algorithm is formulated for identifying the role of plasma networking in observed phenomena of nonlocal (non-diffusive) heat transport in a tokamak.

Kukushkin, A. B.; Rantsev-Kartinov, V. A.

1999-02-01

345

Ablation plasma ion implantation  

NASA Astrophysics Data System (ADS)

The novel hybrid technique, Ablation Plasma Ion Implantation (APII), has been characterized and optimized for ion implantation and/or thin film deposition. In APII, a solid target is ablated by a laser; the resulting plasma plume is the source of ions, which are accelerated to high energy by a negative bias voltage imposed on the substrate. The ions are implanted into the substrate, and the neutral atoms in the ablation plume deposit on the substrate in the form of a thin film. Two configurations of APII are characterized and compared. The parallel target-substrate configuration yields ion-beam-assisted deposition and/or ion implantation, and the perpendicular target-substrate configuration yields pure ion implantation mode. A novel theory of the ion matrix sheath has been developed for APII. The ion current predicted by the Child-Langmuir sheath theory matches well with the experimental ion current. Two different target-substrate orientations have been compared for APII. Parallel target-substrate orientation yields ion-beam-assisted-deposition and ion implantation; to prevent arcing, a laser-voltage delay of several microseconds is required for this mode. For the optimized perpendicular target-substrate orientation, the laser can be fired during the voltage pulse, thereby accelerating ions to full energy. Furthermore, the ion dose is higher than that of the parallel target-substrate orientation by a factor of two. The parameters of plasma plumes have been thoroughly characterized by numerous diagnostics, which include electrical characteristics, optical emission spectroscopy, dye laser resonance absorption photography, resonant/non-resonant interferometry, and Langmuir probe. The total number of ions measured by Langmuir probe, and resonant interferometry, is in the range of 1014 ions per laser pulse. Ion dose measured by plasma diagnostics, has been correlated to the ion dose obtained from material analysis, including sputtering yield calculation, X-ray Energy Dispersive Spectroscopy and X-ray Photoelectron Spectroscopy. The retained and delivered ion doses are in the range of 10 12/cm2 per pulse, which is favorable compared to the ion dose obtained from conventional Plasma Immersion Ion Implantation (PHI). The APII ion implantation efficiency is estimated to be about 2%. Ion acceleration and implantation was demonstrated for both of the APB configurations. The feasibility of APII was verified by Cross-Sectional Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy. For parallel target-substrate configuration, the average deposition rate is 0.0075 nm/shot for the Ti -10 kV APII film. Atomic Force Microscopy implemented at Timken Research Lab indicates that the -4 kV APII film has the smoothest surface. Scratch tests performed at Timken Research lab also prove that APR produces excellent film adhesion.

Qi, Bo

346

Ion plasma waves in dusty plasmas - Halley's comet  

Microsoft Academic Search

Ion waves in a plasma are investigated in the presence of massive charged dust particles, a common space-plasma component now known to exist also in planetary rings and comets. An equation is derived describing low-frequency electrostatic perturbations on a nonhomogeneous background, where the inhomogeneity is due to a distribution of charged grains, each surrounded by an equilibrium statistical distribution of

U. de Angelis; V. Formisano; M. Giordano

1988-01-01

347

Suspension plasma spraying for hydroxyapatite powder preparation by RF plasma  

Microsoft Academic Search

Numerous techniques have been developed to synthesize ceramic powders with improved physical and chemical characteristics. This paper describes a new process called suspension plasma spraying (SPS), based on the use of radio frequency (RF) plasma technology. The objective of SPS is to prepare dense and spherical powders from a suspension of fine (<10 pm) or even ultrafine (<100 nm) powders.

Etienne Bouyer; F. Gitzhofer; M. I. Boulos

1997-01-01

348

EDITORIAL: 80 Years of Plasma 80 Years of Plasma  

Microsoft Academic Search

Irving Langmuir proposed the term 'plasma' in a paper in 1928 (Proc. Natl Acad. Sci. USA 14 627-637) to describe a 'region containing balanced charges of ions and electrons'. There does not appear to be any record of the thinking behind this proposal, so it is difficult to be definitive. One idea is that since the Greek word 'plasma' was

R. N. Franklin; N. St J. Braithwaite

2009-01-01

349

Plasma-wall transition in weakly collisional plasmas  

SciTech Connect

This paper reviews some theoretical and computational aspects of plasma-wall interactions, in particular the formation of sheaths. Some fundamental results are derived analytically using a simple fluid model, and are subsequently tested with kinetic simulations. The various regions composing the plasma-wall transition (Debye sheath, collisional and magnetic presheaths) are discussed in details.

Manfredi, G. [Institut de Physique et Chimie des Materiaux de Strasbourg, BP 43, F-67034 Strasbourg (France); Devaux, S. [Laboratoire de Physique des Milieux Ionises et Applications, Universite Henri Poincare, F-54506 Vandoeuvre-les-Nancy (France)

2008-10-15

350

Experimental results from detached plasmas in TFTR  

SciTech Connect

Detached plasmas are formed in TFTR which have the principal property of the boundary to the high temperature plasma core being defined by a radiating layer. This paper documents the properties of TFTR ohmic-detached plasmas with a range of plasma densities at two different plasma currents.

Strachan, J.D.; Boody, F.P.; Bush, C.E.; Cohen, S.A.; Grek, B.; Grisham, L.; Jobes, F.C.; Johnson, D.W.; Mansfield, D.K.; Medley, S.S.

1986-10-01

351

Drift and mirror modes in magnetized plasmas  

Microsoft Academic Search

Low frequency plasma instabilities driven by plasma inhomogeneity and velocity anisotropies are major candidates for the explanation of various phenomena observed in fusion and space plasmas. For low-beta fusion plasma, the influence of plasma rotation and finite ion temperature on the structure and the type of toroidal drift eigenmodes in tokamaks is investigated rigorously, including the effects induced by the

Ingmar Sandberg

2002-01-01

352

Isolation of Plasma Membrane from Porcine Spermatozoa  

Microsoft Academic Search

A procedure is reported for isolating plasma membrane from porcine spermatozoa. Sperm were separated from gel particles and seminal plasma and subjected to low-intensity sonication that fragmented the plasma membrane, but minimized damage to the acrosome, nucleus and mitochondria. After cytoplasmic droplets and plasma membrane-depleted sperm were removed by differential centrifugation, the plasma membrane fragments were purified by flotation through

D. D. Lunstra; E. D. Clegg; D. J. Morré

1974-01-01

353

The physics of laser plasma interactions  

Microsoft Academic Search

The interactions of laser plasmas are considered theoretically in an introduction for advanced students and practicing scientists. Chapters are devoted to the basic concepts and two-fluid descriptions of plasmas, computer simulations of plasmas using particle codes, EM wave propagation in plasmas, propagation of obliquely incident light waves in inhomogeneous plasmas, collisional absorption of EM waves, and parametric excitation of electron

William L. Kruer

1988-01-01

354

Purification of tantalum by plasma arc melting  

DOEpatents

Purification of tantalum by plasma arc melting. The level of oxygen and carbon impurities in tantalum was reduced by plasma arc melting the tantalum using a flowing plasma gas generated from a gas mixture of helium and hydrogen. The flowing plasma gases of the present invention were found to be superior to other known flowing plasma gases used for this purpose.

Dunn, Paul S. (Santa Fe, NM); Korzekwa, Deniece R. (Los Alamos, NM)

1999-01-01

355

Nonlinear plasma and beam physics in plasma wake-fields  

SciTech Connect

In experimental studies of the Plasma Wake-field Accelerator performed to date at the Argonne Advanced Accelerator Test Facility, significant nonlinearities in both plasma and beam behavior have been observed. The plasma waves driven in the wake of the intense driving beam in these experiments exhibit three-dimensional nonlinear behavior which has as yet no quantitative theoretical explanation. This nonlinearity is due in part to the self-pinching of the driving beam in the plasma, as the denser self-focused beam can excite larger amplitude plasma waves. The self-pinching is a process with interesting nonlinear aspects: the initial evolution of the beam envelope and the subsequent approach to Bennett equilibrium through phase mixing. 35 refs., 10 figs.

Rosenzweig, J.B.

1990-02-12

356

Analysis of First Plasma in Madison Plasma Dynamo Experiment  

NASA Astrophysics Data System (ADS)

The Madison Plasma Dynamo Experiment (MPDX) is designed to investigate the self-generation of magnetic fields in large astrophysical dynamos. Simulations show that an adequately large Magnetic Reynolds number is needed to produce a dynamo; therefore a large, hot, flowing and unmagnetized plasma is necessary. This poster presents an analysis of the first plasma in MPDX using electrodes that both heat and stir the plasma. A lanthanum hexaboride (LaB6) electron source is used within the 3000 Gauss multipole cusp magnetic field and ExB stirring electrodes govern the plasma flow. This poster analyzes the performance of the efficient and fast power supply used in conjunction with the stirring electrodes to create a controllable flow using a feedback loop. In addition, the effectiveness of the LaB6 electron source will be reported. Supported by the DOE and NSF.

Marchbanks, Christopher; Weisberg, David; Wallace, John; Cooper, Christopher; Forest, Cary

2012-10-01

357

Plasma wave propagation with a plasma density gradient  

SciTech Connect

Plasma waves with the plasma diffusion velocity u{sub n} due to a plasma density gradient are described in a positive column plasma. The ion wave is generated by the perturbation of the operating frequency 10{sup 6} s{sup -1} and it propagates with the group velocity u{sub g{approx}}c{sub s}{sup 2}/u{sub n{approx}}(10{sup 5}-10{sup 6}) m/s, where c{sub s} is the acoustic velocity in a fine tube fluorescent lamp, while the electron wave cannot be generated with a turbulence of low frequency less than the electron oscillation frequency {omega}{sub pe}. The propagation of the lighting signal observed in long tube fluorescent lamps is well understood with the propagation of ion waves occurring along the plasma density gradient.

Cho, Guangsup; Choi, Eun-Ha; Uhm, Han Sup [Department of Electrophysics, Kwangwoon University, 447-1 Nowon Wallgye, Seoul 139-701 (Korea, Republic of)

2011-03-15

358

Measurements of plasma potential in high-pressure microwave plasmas.  

PubMed

Plasma potential of a high-pressure ( approximately 1 Torr) microwave-generated argon plasma is measured using a Langmuir probe and a cold emissive probe. The operation of a hot emissive probe in a high-pressure plasma has been very difficult due to frequent burn-outs and significantly reduced lifetime of the probe filament, which, in turn, limits the possibility of collecting a wide range of data. The I-V characteristics from both Langmuir and emissive probes are interpreted using the collisionless probe theory since the collision correction factor is not very significant. The plasma potential determined from both Langmuir and cold emissive probe characteristics agrees well with one another and is observed to be dependent on the operating gas pressure but relatively unchanged as a function of the microwave power. An average plasma potential determined over the operating range of microwave powers varies nonlinearly with the gas pressure. PMID:19405659

Tarasova, A V; Podder, N K; Clothiaux, E J

2009-04-01

359

Plasma acetate turnover and oxidation.  

PubMed Central

Plasma acetate turnover and oxidation were determined in 11 healthy subjects by the constant infusion of a trace amount of [1-14C]acetate for 6 h. The subjects ages ranged from 22 to 57 yr. There was a positive correlation (P less than 0.001) between plasma acetate concentration and turnover rate, and a negative correlation (P less than 0.001) between turnover and age. The plasma acetate concentration in the subjects 22--28 yr old was 0.17 vs. 0.13 mM (P less than 0.02) in subjects 40--57 yr old. The plasma acetate turnover rate was also greater in the younger age group (8.23 +/- 0.66 vs. 4.98 +/- 0.64 mumol/min . kg, P less than 0.01). Approximately 90% of the plasma acetate turnover was immediately oxidized to CO2 in both age groups, however, 13.2 +/- 0.89% of the CO2 output in the younger group was derived from plasma acetate oxidation compared to 7.9 +/- 0.94% in the older group (P less than 0.01). The mean plasma acetate concentration, turnover, and oxidation in six cancer patients 47--63 yr old were similar to the values observed in the age-matched healthy subjects. Uptake or output of acetate by various tissues was measured by arterial-venous plasma acetate concentration differences. In seven of eight subjects undergoing elective surgery, the arterial-portal venous concentration difference was negative, which indicated that the gastrointestinal tract can contribute to plasma acetate production. Uptake of plasma acetate by both the leg and liver appeared to be dictated by the arterial acetate concentration. Net production of acetate by both the leg and liver was most often observed at arterial plasma acetate concentrations less than 0.08 mM.

Skutches, C L; Holroyde, C P; Myers, R N; Paul, P; Reichard, G A

1979-01-01

360

MHD control in burning plasmas MHD control in burning plasmas  

NASA Astrophysics Data System (ADS)

Fusion physics focuses on the complex behaviour of hot plasmas confined by magnetic fields with the ultimate aim to develop a fusion power plant. In the future generation of tokamaks like ITER, the power generated by the fusion reactions substantially exceeds the external input power (Pfusion}/Pin >= 10). When this occurs one speaks of a burning plasma. Twenty per cent of the generated fusion power in a burning plasma is carried by the charged alpha particles, which transfer their energy to the ambient plasma in collisions, a process called thermalization. A new phenomenon in burning plasmas is that the alpha particles, which form a minority but carry a large fraction of the plasma kinetic energy, can collectively drive certain types of magneto-hydrodynamic (MHD) modes, while they can suppress other MHD modes. Both types of MHD modes can have desirable effects on the plasma, as well as be detrimental to the plasma. For example, the so-called sawtooth instability, on the one hand, is largely responsible for the transport of the thermalized alpha particles out of the core, but, on the other hand, may result in the loss of the energetic alphas before they have fully thermalized. A further undesirable effect of the sawtooth instability is that it may trigger other MHD modes such as neoclassical tearing modes (NTMs). These NTMs, in turn, are detrimental to the plasma confinement and in some cases may even lead to disruptive termination of the plasma. At the edge of the plasma, finally, so-called edge localized modes or ELMs occur, which result in extremely high transient heat and particle loads on the plasma-facing components of a reactor. In order to balance the desired and detrimental effects of these modes, active feedback control is required. An additional complication occurs in a burning plasma as the external heating power, which is nowadays generally used for plasma control, is small compared to the heating power of the alpha particles. The scientific challenge in the field of burn control is to find the proper balance between desired and detrimental effects of the various MHD modes and to develop the methods and tools for active feedback control of MHD modes in burning plasmas. Therefore, it is necessary to understand the dynamics of the system, in this case the mutual interactions between the fast alpha particles and the MHD instabilities. Since burning plasmas do not yet exist, the relevant experimental work until ITER comes into full operation needs to be largely based on alpha-particle simulation experiments in which the alpha particles are accelerated to high energies by means of special heating techniques. The precise conditions of a burning plasma can be only partly mimicked in present tokamaks. Hence, also a detailed computational modelling effort is needed, in order to understand the impact of findings in present machines for those of the future. In 2011 two dedicated workshops were devoted to MHD control. Firstly, there was a workshop on Control of Burning Plasmas that took place from 21-25 March 2011 at the Lorentz Centre in Leiden, The Netherlands. Secondly, the 480th Wilhelm and Else Heraeus Seminar that took place from 16-18 June in Bad Honnef, Germany was devoted to Active Control of Instabilities in Hot Plasmas. This special issue presents a collection of papers that have been presented at the two workshops, along with a few papers that are the result of an open call to contribute to this special issue.

Donné, Tony; Liang, Yunfeng

2012-07-01

361

Microaffinity Assay for Plasma Fibronectin.  

National Technical Information Service (NTIS)

The quantitation of fibronectin in human plasma has been based exclusively on immunochemical methods to-date. An alternate method is described which utilizes gelatin-coated Sepharose 4B beads to bind the fibronectin present in plasma, and by a series of w...

N. Catsimpoolas B. Perilli-Palmer A. L. Griffith C. R. Valeri

1983-01-01

362

Inductively Coupled Discharge Plasma Accelerator  

Microsoft Academic Search

Summary form only given. Electromagnetic acceleration for generating an electrically neutral, high flux plasma beam and a system for carrying out this method are studied for the semiconductor etching process having no charging damage and space missions. In the capacitively coupled discharge plasma accelerator, a certain amount of electrode sputtering is inevitable from the ion bombardment flux. This causes serious

V. N. Volynets; Yu. N. Tolmachev; V. G. Pashkovsky; Jinwoo Yoo

2005-01-01

363

Magnetic guiding of laser plasmas  

Microsoft Academic Search

Summary form only given, as follows. The guiding of plasma produced by a KrF laser and Nd:YAG laser using straight and curved solenoidal magnetic field has been studied as a means of giving a debris free, controlled deposition source for the production of thin films. Details on the deflection and guiding of the laser produced plasma in curved and straight

Y. Y. Tsui; D. G. Redman; R. Rankin; C. E. Capjack; D. Vick; R. Fedosejevs

1998-01-01

364

Dispersion Properties of Dusty Plasmas.  

National Technical Information Service (NTIS)

The presence of charged dust particles in a plasma can change its dispersion properties. From the linear response of an equilibrium dusty plasma to the propagation of small perturbations, the authors found an average dielectric function epsilon(omega,k) f...

U. de Angelis R. Bingham V. N. Tsytovich

1989-01-01

365

Waves in Dusty Space Plasmas  

Microsoft Academic Search

In this volume a thorough review is given of waves in dusty plasmas, a fascinating new domain combining plasmas and charged dust, two omnipresent ingredients of the Universe. Spokes and braids observed in the rings of Saturn cannot be explained by gravitation alone, but need the presence of charged dust. Other examples abound, as in zodiacal light, noctilucent clouds, comets

Frank Verheest

2000-01-01

366

Plasma Anodized Lanthanum Titanate Films  

Microsoft Academic Search

This paper discusses the application of plasma anodization to the pyrochlore, lanthanum titanate (La2Ti2O7), and the use of this material as a thin film dielectric. The process involves co-evaporation of the metals, lanthanum and titanium, followed by plasma anodization. Evaporation and anodization techniques are fully discussed as are the electrical properties of the resulting films.

R. E. Whitmore; J. L. Vossen

1965-01-01

367

Model for resonant plasma probe.  

SciTech Connect

This report constructs simple circuit models for a hairpin shaped resonant plasma probe. Effects of the plasma sheath region surrounding the wires making up the probe are determined. Electromagnetic simulations of the probe are compared to the circuit model results. The perturbing effects of the disc cavity in which the probe operates are also found.

Warne, Larry Kevin; Johnson, William Arthur; Hebner, Gregory Albert; Jorgenson, Roy E.; Coats, Rebecca Sue

2007-04-01

368

Gas lens laser produced plasma.  

PubMed

A gas lens is used to focus a megawatt ruby laser beam on to a target to create a plasma. By using focal plane photographs and Faraday cup plasma diagnostics, the focusing ability of a gas lens is compared with an equivalent glass lens. In this experiment the gas lens compares favorably when the laser beam has a divergence of ~1 mrad. PMID:20555544

Notcutt, M; Waltham, J A; Michaelis, M M; Cunningham, P F; Cazalet, R S

1989-07-01

369

Plasma diagnostics by spectroscopic methods.  

PubMed

Spectroscopic techniques for the measurement of plasma parameters are reviewed for a range of temperatures up to 10(6) degrees K. Tables and figures of useful data have been prepared or have been collected from the literature for ready application to experimental measurements. The problem of making spatially resolved intensity measurements in an optically thin axisymmetric plasma column is discussed. PMID:20062112

Robinson, D; Lenn, P D

1967-06-01

370

The modified plasma dispersion function  

Microsoft Academic Search

The modified plasma dispersion function (MPDF), based on the generalized Lorentzian (kappa) particle distribution function, is introduced, and a comprehensive set of graphs of the real and imaginary parts of the MPDF is presented. For any positive integral value of kappa, MPDF is calculated in closed form as a finite series. It is demonstrated how the MPDF approaches the plasma

Danny Summers; Richard M. Thorne

1991-01-01

371

Fully relativistic plasma dispersion function  

Microsoft Academic Search

Properties of a relativistic plasma dispersion function (PDF) that is required for the description of waves propagating perpendicular to a magnetic field in a fully relativistic, magnetized, Maxwellian plasma, are presented. Series, asymptotic series, recurrence relations, integral representations, derivatives, generating functions, approximations, differential equations, and connections with standard transcendental functions are discussed, as are the PDF’s analytic properties.

Le´on P. J. Kamp

1994-01-01

372

Plasma Injection Lance Laboratory Experiments.  

National Technical Information Service (NTIS)

Remelting of ferroalloy fines by blowing the powder through a plasma lance which was immersed into molten metal at 1400C gave a yield of 98% to 99% of the injected metal as molten metal. The injection of solid particles through the plasma flame did not di...

O. Raaness J. Ovsthus S. Prytz

1984-01-01

373

Pellet injection into ATF plasmas  

Microsoft Academic Search

Based on the favorable empirical scaling of stellarator confinement with increasing electron density, pellet fueling is expected to result in significant performance improvement of the ATF plasma. With gas-puff fueling, NBI heated plasmas in ATF are limited by a thermal collapse. Pellet fueling provides a potential means to delay this effect and gain access to the favorable high density confinement

J. B. Wilgen; J. D. Bell; A. C. England; P. W. Fisher; H. C. Howe; M. Murakami; D. A. Rasmussen; R. K. Richards; T. Uckan; W. R. Wing; G. L. Bell; A. L. Qualls; S. Sudo

1990-01-01

374

Hollow Plasma in a Solenoid  

SciTech Connect

A ring cathode for a pulsed, high-current, multi-spot cathodic arc discharge was placed inside a pulsed magnetic solenoid. Photography is used to evaluate the plasma distribution. The plasma appears hollow for cathode positions close the center of the solenoid, and it is guided closer to the axis when the cathode is away from the center.

Anders, Andre; Kauffeldt, Marina; Oks, Efim M.; Roy, Prabir K.

2010-11-30

375

Plasma theory and simulation research  

SciTech Connect

Our research group uses both theory and simulation as tools in order to increase the understanding of instabilities, heating, diffusion, transport and other phenomena in plasmas. We also work on the improvement of simulation, both theoretically and practically. Our focus has been more and more on the plasma edge (the sheath''), interactions with boundaries, leading to simulations of whole devices (someday a numerical tokamak).

Birdsall, C.K.

1989-01-01

376

Global aspects of plasma structures  

Microsoft Academic Search

This topical review provides an overview of the progress achieved under Project 3.1, entitled Global Aspects of Plasma Structures (GAPS) during the lifetime of the Solar Terrestrial Energy Program (STEP) from 1990–97. The mandate of the GAPS project covered middle and high latitude plasma structuring. However, given the requirement of limited length for this overview, only high latitude studies will

Sunanda Basu; Cesar Valladares

1999-01-01

377

Electron Interactions in Reactive Plasmas  

Microsoft Academic Search

Gas discharge plasmas are complex systems that consist of various groups of interacting particles such as neutral gas atoms and molecules in the ground state or in excited states, electrons, ions, and photons. In principle, one needs to understand and describe all possible interactions between these particles in order to model the properties of the plasma and to predict its

Kurt Becker

2001-01-01

378

Doppler Shift in a Plasma.  

National Technical Information Service (NTIS)

It is first shown that the ideal electron plasma (presence of protons neglected) is unique among all dispersive media in that it does not distinguish any inertial frame of reference in terms of utility. The theory of the Doppler shift in an ideal plasma i...

B. Manz

1968-01-01

379

Advanced plasma technology in microelectronics  

Microsoft Academic Search

The current status and future trends of plasma technology for microelectronics are discussed. The low pressure high density plasma (HDP) source is advantageous for the etching of a gate electrode and a small deep contact hole. However, the high temperature electrons in the HDP may induce profile defects, notch and sidewall etching, and may degrade the electrical quality of the

C. O Jung; K. K Chi; B. G Hwang; J. T Moon; M. Y Lee; J. G Lee

1999-01-01

380

The plasma system of RFX  

Microsoft Academic Search

The “plasma system” of RFX includes the first wall, the vacuum vessel, the stabilizing shell, the vacuum and gas injection system, the remote handling system and the relevant auxiliary plants (cooling, baking, glow discharge cleaning, etc.).Since no limiters are provided, the full energy and particle flux from the plasma must be absorbed by the first wall. Taking into account the

F Gnesotto; P Sonato; W. R Baker; A Doria; F Elio; M Fauri; P Fiorentin; G Marchiori; G Zollino

1995-01-01

381

Industrial applications of thermal plasmas  

Microsoft Academic Search

The main characteristics and applications of thermal plasmas are reviewed here. The industrial applications of thermal plasmas can be divided in: low power–cutting, welding, spraying; metallurgical and steelmaking; materials; environment. Some of the processes described in this article include: powder spraying, metal refining, tundish and laddle heating, production of ferroalloys and ceramic materials, and treatment of residues (aluminum scrap, steel

Roberto Nunes Szente

1995-01-01

382

Industrial plasma torches and applications  

Microsoft Academic Search

Plasma technology has given a new direction and impetus to many industrial operations by opening up a new range of mechanical, chemical and metallur- gical processing techniques. The high temperatures together with the high reactivity due to the presence of free ions and radicals, make the plasma a powerful medium to promote high heat transfer rates and chemical reactions. This

N. Venkatramani

383

How to model quantum plasmas  

Microsoft Academic Search

Traditional plasma physics has mainly focused on regimes characterized by high temperatures and low densities, for which quantum-mechanical effects have virtually no impact. However, recent technological advances (particularly on miniaturized semiconductor devices and nanoscale objects) have made it possible to envisage practical applications of plasma physics where the quantum nature of the particles plays a crucial role. Here, I shall

Giovanni Manfredi

2005-01-01

384

Collective quantum scattering in plasma  

Microsoft Academic Search

Collective quantum plasma effects in scattering of photons on electrons are derived. The generalization of Klein-Nishina scattering is obtained. The dependence of scattering on the collective plasma parameter and the ratio of the photon energy to the electron thermal energy is investigated.

V. N. Tsytovich

1996-01-01

385

Plasma homocysteine and menopausal status.  

PubMed

The aim of the study was to measure the concentrations of plasma homocysteine in premenopausal and postmenopausal women, and to examine a possible relationship between plasma homocysteine and oestrogen status. Homocysteine metabolism was studied by a standardized oral methionine loading test, and oestrogen status was assessed by the measurement of serum 17 beta-oestradiol. Forty-six premenopausal and 26 postmenopausal healthy women without a history of vascular disease or adverse pregnancy outcome were recruited by public advertisement. The main outcome measures were the concentrations of fasting and postmethionine plasma homocysteine, and serum 17 beta-oestradiol. Fasting plasma homocysteine concentrations (mean +/- SD) were significantly higher in postmenopausal women as compared to premenopausal women (12 +/- 4 mumol L-1 and 10 +/- 3 mumol L-1, respectively) as well as postmethionine plasma homocysteine concentrations (46 +/- 16 mumol L-1 and 32 +/- 9 mumol L-1, respectively). In premenopausal women, postmethionine plasma homocysteine was negatively and significantly correlated to serum 17 beta-oestradiol (r = -0.34). It is concluded that plasma homocysteine concentrations, both fasting and after methionine loading, are significantly higher in postmenopausal women than in premenopausal women. In premenopausal women, the higher concentrations of serum 17 beta-oestradiol may account in part for the lower concentrations of postmethionine plasma homocysteine. PMID:8582443

Wouters, M G; Moorrees, M T; van der Mooren, M J; Blom, H J; Boers, G H; Schellekens, L A; Thomas, C M; Eskes, T K

1995-11-01

386

Biocompatibility of plasma nanostructured biopolymers  

NASA Astrophysics Data System (ADS)

Many areas of medicine such as tissue engineering requires not only mastery of modification techniques but also thorough knowledge of the interaction of cells with solid state substrates. Plasma treatment can be used to effective modification, nanostructuring and therefore can significantly change properties of materials. In this work the biocompatibility of the plasma nanostructured biopolymers substrates was studied. Changes in surface chemical structure were studied by X-ray photoelectron spectroscopy (XPS). The morphology pristine and modified samples were determined using atomic force microscopy (AFM). The surface wettability was determined by goniometry from contact angle. Biocompatibility was determined by in vitro tests, the rat vascular smooth muscle cells (VSMCs) were cultivated on the pristine and plasma modified biopolymer substrates. Their adhesion, proliferation, spreading and homogeneous distribution on polymers was monitored. It was found that the plasma treatment leads to rapid decrease of contact angle for all samples. Contact angle decreased with increasing time of modification. XPS measurements showed that plasma treatment leads to changes in ratio of polar and non-polar groups. Plasma modification was accompanied by a change of surface morphology. Biological tests found that plasma treatment have positive effect on cells adhesion and proliferation cells and affects the size of cell's adhesion area. Changes in plasma power or in exposure time influences the number of adhered and proliferated cells and their distribution on biopolymer surface.

Slepi?ková Kasálková, N.; Slepi?ka, P.; Ba?áková, L.; Sajdl, P.; Švor?ík, V.

2013-07-01

387

Characteristics of multiarc plasma devices  

Microsoft Academic Search

Multiarc plasma devices such as plasmatrons operate with lower arc currents than single-arc counterparts, which not contributes to a higher efficiency but also extends the life of electrodes. Typically, reduction of the arc current for producing an air plasma from 400 A to 100 A or further to 50 A lengthens the life of zirconium electrodes from 24 h to

V. S. Klubnikin; B. G. Smirnov

1985-01-01

388

Plasma digital density determining device  

DOEpatents

The density of a decaying plasma in an electrically conducting enclosure is determined by applying an excitation to the cavity formed by the enclosure and counting digitally the number of resonant frequencies traversed by the combination of the cavity and the decaying plasma.

Sprott, Julien C. (Madison, WI); Lovell, Thomas W. (Madison, WI); Holly, Donald J. (Madison, WI)

1976-01-01

389

Negative Plasma Densities Raise Questions.  

National Technical Information Service (NTIS)

Lawrence Livermore scientists study the physics of plasmas in their pursuit to create fusion energy, because plasmas are an integral part of that process. When deuterium and tritium are heated to the extreme temperatures needed to achieve and sustain a fu...

A. Hazi

2006-01-01

390

Density and temperature measurements in a large volume plasma of relevance to plasma neutralizers  

Microsoft Academic Search

Results are presented of density and temperature measurements made within a large volume magnetically confined plasma which could be applicable to a plasma neutralizer. rf power at a few megahertz is inductively coupled into an argon plasma by means of a multi-turn insulated antenna within the plasma chamber. This large volume, dense plasma offers potential advantages over an equivalent plasma

L. M. Lea; S. B. Schneider; A. J. T. Holmes

1992-01-01

391

Plasma diagnostics and plasma-surface interactions in inductively coupled plasmas  

NASA Astrophysics Data System (ADS)

The semiconductor industry's continued trend of manufacturing device features on the nanometer scale requires increased plasma processing control and improved understanding of plasma characteristics and plasma-surface interactions. This dissertation presents a series of experimental results for focus studies conducted in an inductively coupled plasma (ICP) system. First novel "on-wafer" diagnostic tools are characterized and related to plasma characteristics. Second, plasma-polymer interactions are characterized as a function of plasma species and processing parameters. Complementary simulations accompany each focus study to supplement experimental findings. Wafer heating mechanisms in inductively coupled molecular gas plasmas are explored with PlasmaTemp(TM), a novel "on-wafer" diagnostic tool. Experimental wafer measurements are obtained with the PlasmaTemp(TM) wafer processed in argon (Ar) and argon-oxygen (Ar/O2) mixed plasmas. Wafer heating mechanisms were determined by combining the experimental measurements with a 3-dimensional heat transfer model of the wafer. Comparisons between pure Ar and Ar/O2 plasmas demonstrate that two additional wafer heating mechanisms can be important in molecular gas plasmas compared to atomic gas discharges. Thermal heat conduction from the neutral gas and O-atom recombination on wafer surface can contribute as much as 60% to wafer heating under conditions of low-energy ion bombardment in molecular plasmas. Measurements of a second novel "on-wafer" diagnostic sensor, the PlasmaVolt(TM), were tested and validated in the ICP system for Ar plasmas varying in power and pressure. Sensor measurements were interpreted with a numerical sheath simulation and comparison to scaling laws derived from the inhomogeneous sheath model. The study demonstrates sensor measurements are proportional to the RF-current through the sheath and the scaling is a function of sheath impedance. PlasmaVolt(TM) sensor measurements are proportional to the square root of the plasma density at the plasma-sheath interface, one-fourth root of the electron temperature, and one-fourth root of the RF bias voltage under conditions where the sheath is predominantly capacitive. When the sheath impedance becomes increasingly resistive, the sensor measurements deviate from the scaling law and tend to be directly proportional to the plasma density. Vacuum ultraviolet (VUV) emissions in Ar ICPs are characterized and the chemical and physical modifications to 193 nm photoresist (PR) polymer materials processed in Ar ICPs are investigated. Fourier transform infrared (FTIR) transmission measurements as a function of VUV photon fluence demonstrate that VUV-induced bond breaking occurs over a period of time. A numerical model demonstrates that VUV photons deplete near-surface O-containing bonds, leading to deeper, subsequent penetration and more bond losses, while the remaining near-surface C--C bonds absorb the incident radiation and slow VUV photon penetration. The roughening mechanism of blanket and patterned 193 nm PR samples are explored in a well characterized Ar ICP. FTIR and atomic force microscopy (AFM) analysis of plasma processed 193 nm PR suggests that ion-induced generation of a graphitized layer at high energies, combined with VUV bulk modification of 193 nm PR may initiate PR roughening. The roughness of blanket samples increases as a function of VUV fluence, ion energy, and substrate temperature. Line width roughness (LWR) measurements of patterned samples demonstrate a similar trend suggesting that LWR may correlate with surface roughness of patterns. The results are compared to PR studies previously conducted in an ultra-high vacuum beam system demonstrating that the vacuum beam system is a useful tool that can deconvolute and simplify complex plasma systems.

Titus, Monica Joy

392

Advances in plasma melting technology  

NASA Astrophysics Data System (ADS)

The quest for 'defect-free' high performance metals has benefited from the expansion of plasma hearth melting capacity. 'Skull' melting in water-cooled copper containers under an inert gas atmosphere allows elimination of ceramic and refractory metal inclusions when melting reactive metals and superalloys, while retaining the input alloy content. The interactions of operating variables such as furnace pressure, nature of gas, arc current and heat input pattern with product properties such as homogeneity, grain size, and inclusions are described. By proper process control, plasma hearth melting has been qualified as one of only two processes suitable for particularly demanding rotating grade engine parts made of titanium alloy. Costs of plasma hearth melting are less than with electron beam. Extension of plasma processing to other alloys is being actively pursued. Powder production is currently practical with plasma melting and bottom pouring to make powder. Some speculations on future trends in materials and operating temperatures are offered.

Eschenbach, R.; Hoffelner, W.

393

Anisotropic plasma crystal solitons.  

PubMed

An analytical two-dimensional model for weakly dispersive and weakly nonlinear longitudinal and transverse shear waves propagating in an ideal two-dimensional hexagonal Yukawa crystal is presented. The model takes into account the nonlinear terms up to the third order. Both compressional and shear soliton solutions are found in the long-wavelength approximation. It is shown that the compressional solitons are always supersonic and weakly anisotropic. The shear solitons, on the other hand, exhibit strong anisotropy and can be both subsonic and supersonic, depending on the direction of propagation. In the model, shear solitons cannot propagate along the main axes. The role of weak damping as well as formation of multiple solitons is analyzed. The results are discussed in connection with wave and Mach cone experiments in a monolayer hexagonal plasma crystal, and a diagnostic method is proposed to measure both the charge of the microparticles and the lattice parameter. PMID:12241301

Zhdanov, S K; Samsonov, D; Morfill, G E

2002-08-26

394

Waves in Space Plasmas  

NASA Astrophysics Data System (ADS)

Applications of linear mode conversion at Alfven/ion-ion hybrid resonances and at electron plasma frequency have been discussed. Alfven resonances play an important role on energy transport the outer to inner regions of magnetospheres. At Earth's magnetopause, the mode-converted kinetic Alfven waves also lead to solar wind particle entry and transverse ion heating. IIH resonant waves can explain of the generation of linearly polarized EMIC waves at Earth. Compressional waves can also interact with Mercury's magnetosphere exciting IIH resonances as global eigenmodes. Linear mode conversion (LMC) from Langmuir to electromagnetic waves is relevant to explain type II and III radio bursts. Through the LMC, both right- and left-hand polarized wave modes are produced and it provides the solutions for linear/partial polarized type II and III problems.

Kim, Eun-Hwa; Johnson, Jay R.; Cairns, Iver H.; Lee, Dong-Hun

2009-11-01

395

Waves in Space Plasmas  

SciTech Connect

Applications of linear mode conversion at Alfven/ion-ion hybrid resonances and at electron plasma frequency have been discussed. Alfven resonances play an important role on energy transport the outer to inner regions of magnetospheres. At Earth's magnetopause, the mode-converted kinetic Alfven waves also lead to solar wind particle entry and transverse ion heating. IIH resonant waves can explain of the generation of linearly polarized EMIC waves at Earth. Compressional waves can also interact with Mercury's magnetosphere exciting IIH resonances as global eigenmodes. Linear mode conversion (LMC) from Langmuir to electromagnetic waves is relevant to explain type II and III radio bursts. Through the LMC, both right- and left-hand polarized wave modes are produced and it provides the solutions for linear/partial polarized type II and III problems.

Kim, Eun-Hwa; Johnson, Jay R. [Princeton Plasma Physics Laboratory, Princeton University, NJ 08543 (United States); Cairns, Iver H. [School of Physics, University of Sydney, Sydney NSW 2001 (Australia); Lee, Dong-Hun [Department of Astronomy and Space Science, Kyung Hee University, Yongin, Kyunggi 449-701 (Korea, Republic of)

2009-11-26

396

Plasma Dispersion Function for the Kappa Distribution.  

National Technical Information Service (NTIS)

The plasma dispersion function is computed for a homogeneous isotropic plasma in which the particle velocities are distributed according to a Kappa distribution. An ordinary differential equation is derived for the plasma dispersion function and it is sho...

J. J. Podesta

2004-01-01

397

21 CFR 866.2160 - Coagulase plasma.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Coagulase plasma. 866.2160 Section 866.2160 Food...Microbiology Devices § 866.2160 Coagulase plasma. (a) Identification. Coagulase plasma is a device that consists of...

2013-04-01

398

Atmospheric-Pressure Plasma Process and Applications.  

National Technical Information Service (NTIS)

This paper provides a general discussion of atmospheric-pressure plasma generation, processes, and applications. There are two distinct categories of atmospheric-pressure plasmas: thermal and nonthermal. Thermal atmospheric-pressure plasmas include those ...

P. Kong

2006-01-01

399

Control of impurities in toroidal plasma devices  

DOEpatents

A method and apparatus for plasma impurity control in closed flux plasma systems such as Tokamak reactors is disclosed. Local axisymmetrical injection of hydrogen gas is employed to reverse the normally inward flow of impurities into the plasma.

Ohkawa, Tihiro (La Jolla, CA)

1980-01-01

400

Gyrotrons for Plasma Heating  

NASA Astrophysics Data System (ADS)

Advances in gyrotron research have led to a new generation of devices that can operate at the megawatt power level at frequencies up to 170 GHz. These gyrotrons allow electron cyclotron heating (ECH) of plasmas to be conducted at the multimegawatt power levels needed for heating present day tokamaks and stellarators. In recent years, several breakthroughs have occurred in research on gyrotrons. These new insights involve major advances in both the physics of beams and the physics of coherent generation of microwave radiation. Gyrotron electron beams have now been produced at currents of up to 100A at up to 100 kV with excellent beam quality. New diagnostic techniques have been developed to measure this improved beam quality. Research in the physics of microwave generation has included the development of new codes which can predict mode competition in the highly overmoded gyrotron cavity. Experimental results agree well with theory. Gyrotron efficiency has risen to over 50% using the depressed collector. Other advances in the field of gyrotron research include the development of the diamond window, which allows over 1 MW of continuous power to be transmitted, and the development of new mode converters which efficiently transform the high order mode of the gyrotron cavity into a Gaussian beam in free space. Future goals of gyrotron research include going to higher power levels, in the 2 to 5 MW range, achieving higher efficiency, up to 75% using a multi-stage depressed collector, and achieving a wide range of frequency tunability, possibly up to a 25% bandwidth. Progress on ancillary components of an ECH system such as waveguides and antennas has also been impressive. This research has led to many "spinoffs" including gyrotrons for radar and industrial heating. When fully developed, ECH systems could possibly be the least expensive and most reliable means of auxiliary heating of plasmas.

Temkin, Richard

1998-11-01

401

NCSX Plasma Heating Methods  

SciTech Connect

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.

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

2003-02-28

402

NCSX Plasma Heating Methods  

SciTech Connect

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.

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

2008-01-18

403

Ultracold Neutral Plasma Density Waves  

NASA Astrophysics Data System (ADS)

Ultracold neutral plasmas, which are created by photoionizing laser cooled atoms near the ionization threshold, have been extensively studied in order to probe strong Coulomb coupling effects, low-energy atomic processes, equilibration, and collective phenomena [1]. The experimental study of collective modes, however, has previously been limited to phenomena involving electrons. By spatially modulating the intensity pattern of the photoionizing laser, we are now able to create controlled density perturbations on the plasma, which enables study of ion collective behavior. Periodic modulation excites ion acoustic waves [2]. We have also created two distinct plasmas that stream into each other. In the hydrodynamic regime, the central gap between the two plasmas splits into two density ``holes'' that propagate away from the plasma center at the ion acoustic velocity. At lower densities and higher particle velocities, plasmas are less collisional, and we observe kinetic effects such as plasma streams penetrating each other, with a penetration depth that reflects the ion stopping power. This general technique for sculpting the density opens many new possibilities, such as investigation of non-linear phenomena, instabilities, and shock waves in the ultracold regime, and determination of the effects of strong coupling on dispersion relations. The low temperature, small size, plasma expansion, and strongly coupled nature of ultracold plasmas make these studies fundamentally interesting. They may also shed light on similar phenomena in high energy density, laser-produced plasmas that can be near the strongly coupled regime. [4pt] [1] T. C. Killian, T. Pattard, Thomas Pohl, and J. M. Rost, Phys. Rep., 449, 77 (2007).[0pt] [2] J. Castro, P. McQuillen, and T. C. Killian, Phys. Rev. Lett. 105, 065004 (2010).

Killian, Thomas

2012-06-01

404

Landau damping in space plasmas  

SciTech Connect

Space plasmas typically possess a particle distribution function with an enhanced high-energy tail that is well modeled by a generalized Lorentzian (or kappa) distribution with spectral index {kappa}. The modified plasma dispersion function {bold Z}{sup *}{sub {kappa}}({xi}) is employed to analyze the Landau damping of (electrostatic) Langmuir waves and ion-acoustic waves in a hot, isotropic, unmagnetized, generalized Lorentzian plasma, and the solutions are compared with the classical results for a Maxwellian plasma. Numerical solutions for the real and imaginary parts of the wave frequency {omega}{sub 0}{minus}{ital i}{gamma} are obtained as a function of the normalized wave number {ital k}{lambda}{sub D}, where {lambda}{sub D} is the electron Debye length. For both particle distributions the electrostatic modes are strongly damped, {gamma}/{omega}{sub 0}{much gt}1, at short wavelengths, {ital k}{lambda}{sub D}{much gt}1. This collisionless damping becomes less severe at long wavelengths, {ital k}{lambda}{sub D}{much lt}1, but the attenuation of Langmuir waves is much stronger for a generalized Lorentzian plasma than for a Maxwellian plasma. This will further localize Langmuir waves to frequencies just above the electron plasma frequency in plasmas with a substantial high-energy tail. Landau damping of ion-acoustic waves is only slightly affected by the presence of a high-energy tail, but is strongly dependent on the ion temperature. Owing to the simple analytical form of the modified plasma dispersion function when {kappa}=2 (corresponding to a pronounced high-energy tail), exact analytical results for the real and imaginary parts of the wave frequency can be found in this case; similar solutions are not available for a Maxwellian plasma.

Thorne, R.M. (Department of Atmospheric Sciences, University of California at Los Angeles, Los Angeles, California 90024-1565 (USA)); Summers, D. (Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland A1C 5S7 Canada (CA))

1991-08-01

405

Use of plasma volume substitutes and plasma in developing countries.  

PubMed

Plasma and plasma substitutes are used in the treatment of various conditions such as haemorrhage and shock. This article examines the role of crystalloids, artificial colloids, human plasma, human albumin, and plasma protein fraction, in the treatment of such patients, with particular reference to peripheral health facilities in developing countries.It is concluded that 0.9% saline, together with 5-6% dextrose, is of particular importance in this situation since it is easy to produce locally, is stable at high temperatures, and has a low cost/benefit ratio. The second priority is to ensure the availability of a limited quantity of one or more colloid plasma substitutes. In the field of plasma, fresh frozen or fresh liquid plasma is most useful for the treatment of various haemostatic derangements and follow-up treatment of severe burns, since it contains the widest spectrum of therapeutically useful components and can be produced locally with an acceptable degree of difficulty.The treatment of severe diarrhoea with special alkaline electrolyte solutions and oral rehydration solutions is also outlined. PMID:6188548

Lundsgaard-Hansen, P; Collins, J A; David-West, A S; Lopez, C G; Hantchef, Z S; Lothe, F; von Steffens, E

1983-01-01

406

Surface plasma source with anode layer plasma accelerator  

SciTech Connect

Proposed plasma generation system can be used for high current negative ion beam production and for directed deposition by flux of sputtered neutrals and negative ions. The main mechanism of negative ion formation in surface plasma sources is the secondary emission from low work function surface bombarded by a flux of positive ion or neutrals. The emission of negative ions is enhanced significantly by introducing a small amount of cesium or other substance with low ionization potential. In the proposed source are used positive ions generated by Hall drift plasma accelerator (anode layer plasma accelerator or plasma accelerator with insulated channel, with cylindrical or race track configuration of emission slit). The target-emitter is bombarded by the ion beam accelerated in crossed ExB fields. Negative ions are extracted from the target surface with geometrical focusing and are accelerated by negative voltage applied between emitter and plasma, contacting with the plasma accelerator. Hall drift ion source has a special design with a space for passing of the emitted negative ions and sputtered particles through the positive ion source.

Dudnikov, Vadim [Muons, Inc., Batavia, Illinois 60510 (United States)

2012-02-15

407

A new plasma potential measurement instrument for plasma ion sources  

SciTech Connect

A very efficient and fast instrument to measure the plasma potential of ion sources has been developed at the Department of Physics, University of Jyvaeskylae (JYFL). The operating principle of this novel instrument is to apply a decelerating voltage into a mesh located in the beamline of the ion source. The plasma potential is determined by measuring the current at the grounded electrode situated behind the mesh as a function of the voltage. In this article, we will introduce the instrument and the first results. In the experiments, the instrument was connected to the beamline of the JYFL 6.4 GHz electron cyclotron resonance ion source. The plasma potential was measured with different source conditions and it was observed to vary between 30-65 V. The plasma potential tended to increase as the microwave power, or the gas feed rate, was increased. These results are consistent with earlier observations and estimations. It was also noticed that the value of the plasma potential changed when the negative voltage applied to the biased disk at the injection of the ion source was varied. Complementary to optical plasma diagnostics, such an instrument can be used as a very efficient tool to get a precise relationship between plasma conditions and extracted beams.

Tarvainen, O.; Suominen, P.; Koivisto, H. [Department of Physics, Accelerator Laboratory, University of Jyvaeskylae, P.O. Box 35, FIN-40014, University of Jyvaeskylae (Finland)

2004-10-01

408

Use of plasma volume substitutes and plasma in developing countries*  

PubMed Central

Plasma and plasma substitutes are used in the treatment of various conditions such as haemorrhage and shock. This article examines the role of crystalloids, artificial colloids, human plasma, human albumin, and plasma protein fraction, in the treatment of such patients, with particular reference to peripheral health facilities in developing countries. It is concluded that 0.9% saline, together with 5-6% dextrose, is of particular importance in this situation since it is easy to produce locally, is stable at high temperatures, and has a low cost/benefit ratio. The second priority is to ensure the availability of a limited quantity of one or more colloid plasma substitutes. In the field of plasma, fresh frozen or fresh liquid plasma is most useful for the treatment of various haemostatic derangements and follow-up treatment of severe burns, since it contains the widest spectrum of therapeutically useful components and can be produced locally with an acceptable degree of difficulty. The treatment of severe diarrhoea with special alkaline electrolyte solutions and oral rehydration solutions is also outlined.

Lundsgaard-Hansen, P.; Collins, J. A.; David-West, A. S.; Lopez, C. G.; Hantchef, Z. S.; Lothe, F.; von Steffens, E.

1983-01-01

409

High-beta plasma blobs in the morningside plasma sheet  

NASA Astrophysics Data System (ADS)

Equator-S frequently encountered, i.e. on 30% of the orbits between 1 March and 17 April 1998, strong variations of the magnetic field strength of typically 5-15-min duration outside about 9RE during the late-night/early-morning hours. Very high-plasma beta values were found, varying between 1 and 10 or more. Close conjunctions between Equator-S and Geotail revealed the spatial structure of these plasma blobs and their lifetime. They are typically 5-10° wide in longitude and have an antisymmetric plasma or magnetic pressure distribution with respect to the equator, while being altogether low-latitude phenomena (< 15°). They drift slowly sunward, exchange plasma across the equator and have a lifetime of at least 15-30 min. While their spatial structure may be due to some sort of mirror instability, little is known about the origin of the high-beta plasma. It is speculated that the morningside boundary layer somewhat further tailward may be the source of this plasma. This would be consistent with the preference of the plasma blobs to occur during quiet conditions, although they are also found during substorm periods. The relation to auroral phenomena in the morningside oval is uncertain. The energy deposition may be mostly too weak to generate a visible signature. However, patchy aurora remains a candidate for more disturbed periods.

Haerendel, G.; Baumjohann, W.; Georgescu, E.; Nakamura, R.; Kistler, L. M.; Klecker, B.; Kucharek, H.; Vaivads, A.; Mukai, T.; Kokubun, S.

1999-12-01

410

Meter scale plasma source for plasma wakefield experiments  

NASA Astrophysics Data System (ADS)

High accelerating gradients generated by a high density electron beam moving through plasma has been used to double the energy of the SLAC electron beam [1]. During that experiment, the electron current density was high enough to generate its own plasma without significant head erosion. In the newly commissioned FACET facility at SLAC, the peak current will be lower and without pre-ionization, head erosion will be a significant challenge for the planned experiments. In this work we report on our design of a meter scale plasma source for these experiments to effectively avoid the problem of head erosion. The plasma source is based on a homogeneous metal vapor gas column that is generated in a heat pipe oven [2]. A lithium oven over 30 cm long at densities over 1017 cm-3 has been constructed and tested at UCLA. The plasma is then generated by coupling a 10 TW short pulse Ti:Sapphire laser into the gas column using an axicon lens setup. The Bessel profile of the axicon setup creates a region of high intensity that can stretch over the full length of the gas column with approximately constant diameter. In this region of high intensity, the alkali metal vapor is ionized through multi-photon ionization process. In this manner, a fully ionized meter scale plasma of uniform density can be formed. Methods for controlling the plasma diameter and length will also be discussed.

Vafaei-Najafabadi, N.; Shaw, J. L.; Marsh, K. A.; Joshi, C.; Hogan, M. J.

2012-12-01

411

The Behavior of Ionospheric Plasma in Topside Equatorial Plasma Structures  

NASA Astrophysics Data System (ADS)

The DMSP spacecraft provides a unique view of topside plasma structures by frequently passing through a single depletion spanning a range of magnetic flux tube apex heights within it. This allows us to investigate the relationships between the evolving envelope of the structure and the plasma within it. In this report we describe the results of initial investigations where the angle between the satellite trajectory and plasma depletion allows different regions inside a bubble to be sampled. In particular we examine the relationships between the gradient in the vertical flow inside a bubble and the bubble width in longitude at different magnetic field apex heights.

Venkatraman, S. A.; Heelis, R. A.; Coley, W. R.

2006-05-01

412

Plasma Dark Current in Self-Ionized Plasma Wakefield Accelerators  

SciTech Connect

Evidence of particle trapping has been observed in a beam driven Plasma Wake Field Accelerator (PWFA) experiment, E164X, conducted at the Stanford Linear Accelerator Center by a collaboration which includes USC, UCLA and SLAC. Such trapping produces plasma dark current when the wakefield amplitude is above a threshold value and may place a limit on the maximum acceleration gradient in a PWFA. Trapping and dark current are enhanced when in an ionizing plasma, that is self-ionized by the beam. Here we present experimental results.

Oz, E.; Deng, S.; Katsouleas, T.; Muggli, P.; /Southern California U.; Iverson, R.; Johnson, D.K.; Krejcik, P.; O'Connell, C.; Siemann, R.H.; Walz, D.; /SLAC; Clayton, C.E.; Huang, C.; Joshi, C.; Lu, W.; Marsh, K.A.; Mori, W.B.; Zhou, M.; /UCLA

2006-01-30

413

Negative Plasma Densities Raise Questions  

SciTech Connect

Nearly all the matter encountered on Earth is either a solid, liquid, or gas. Yet plasma-the fourth state of matter-comprises more than 99 percent of the visible universe. Understanding the physical characteristics of plasmas is important to many areas of scientific research, such as the development of fusion as a clean, renewable energy source. Lawrence Livermore scientists study the physics of plasmas in their pursuit to create fusion energy, because plasmas are an integral part of that process. When deuterium and tritium are heated to the extreme temperatures needed to achieve and sustain a fusion reaction (about 100 million degrees), the electrons in these light atoms become separated from the nuclei. This process of separation is called ionization, and the resulting collection of negatively charged free electrons and positively charged nuclei is known as a plasma. Although plasmas and gases have many similar properties, plasmas differ from gases in that they are good conductors of electricity and can generate magnetic fields. For the past decade, x-ray laser interferometry has been used in the laboratory for measuring a plasma's index of refraction to determine plasma density. (The index of refraction for a given material is defined as the wavelength of light in a vacuum divided by the wavelength of light traveling through the material.) Until now, plasma physicists expected to find an index of refraction less than one. Researchers from Livermore and Colorado State University recently conducted experiments on aluminum plasmas at the Laboratory's COMET laser facility and observed results in which the index of refraction was greater than one. This surprising result implied a negative electron density. Livermore physicist Joseph Nilsen and his colleagues from Livermore and the University of Notre Dame have performed sophisticated calculations to explain this phenomenon. Previously, researchers believed that only free electrons contributed to the index of refraction. Nilsen and his colleagues posit that bound electrons attached to the ions in plasmas can greatly affect the index of refraction and make it greater than one. Furthermore, if the effect of bound electrons is ignored when analyzing experimental results from x-ray interferometry, the electron density of plasmas may be indeterminate or significantly under- or overestimated.

Hazi, A

2006-01-26

414

Cold plasma decontamination of foods.  

PubMed

Cold plasma is a novel nonthermal food processing technology that uses energetic, reactive gases to inactivate contaminating microbes on meats, poultry, fruits, and vegetables. This flexible sanitizing method uses electricity and a carrier gas, such as air, oxygen, nitrogen, or helium; antimicrobial chemical agents are not required. The primary modes of action are due to UV light and reactive chemical products of the cold plasma ionization process. A wide array of cold plasma systems that operate at atmospheric pressures or in low pressure treatment chambers are under development. Reductions of greater than 5 logs can be obtained for pathogens such as Salmonella, Escherichia coli O157:H7, Listeria monocytogenes, and Staphylococcus aureus. Effective treatment times can range from 120 s to as little as 3 s, depending on the food treated and the processing conditions. Key limitations for cold plasma are the relatively early state of technology development, the variety and complexity of the necessary equipment, and the largely unexplored impacts of cold plasma treatment on the sensory and nutritional qualities of treated foods. Also, the antimicrobial modes of action for various cold plasma systems vary depending on the type of cold plasma generated. Optimization and scale up to commercial treatment levels require a more complete understanding of these chemical processes. Nevertheless, this area of technology shows promise and is the subject of active research to enhance efficacy. PMID:22149075

Niemira, Brendan A

2011-12-09

415

Plasma-Jet Convergence Calculations  

NASA Astrophysics Data System (ADS)

Converging plasma jets may be able to reach the regime of high energy density plasmas (HEDP, ˜10^11 J m-3). If plasma jets can be used for magneto-inertial fusion (MIF) [1], the resulting heating by fusion products might generate even higher energy density plasmas. This poster reports the results of using the UW's 1D Lagrangian, rad-hydro, fusion code BUCKY to investigate two cases of converging plasma jets formulated in Ref. 2. The BUCKY code solves single-fluid equations of motion with ion-electron interactions, PdV work, table-lookup equations of state, fast-ion energy deposition, and one or two temperatures. Extensions to the code include magnetic field evolution as the plasmoid compresses, B-field pressure, plus dependence of the thermal conductivity on the magnetic field. Some parametric explorations are also reported. [4pt] [1] Y.C. F. Thio, et al.,``Magnetized Target Fusion in a Spheroidal Geometry with Standoff Drivers,'' in Current Trends in Int'l Fusion Research, E. Panarella, ed. (NRC--Canada, Ottawa, Canada, 1999), p. 113. [2] R. Samulyak, P. Parks, and L. Wu, ``Spherically Symmetric Simulation of Plasma Liner Driven Magnetoinertial Fusion,'' Physics of Plasmas 17, 092702 (2010).

Santarius, John

2011-11-01

416

Light ion helicon plasma sources  

NASA Astrophysics Data System (ADS)

Helicon plasma sources are capable of producing high density plasma using steady state solenoid or mirror-like magnetic fields with a wide variety of gases. Power to produce the plasma is supplied by various antenna configurations driven at frequencies typically ranging from 1 to 50 MHz. The ability to obtain high plasma densities with high fractional ionization using readily available, low-cost components makes the helicon an attractive plasma source for many applications including plasma rocket propulsion, fusion component testing, and materials processing. However, their operation can be a sensitive function of the magnetic field strength and geometry as well as the driving frequency, especially when using light feedstock gases such as hydrogen or helium. This sensitivity can make it difficult to design a helicon source with the characteristics required for a specific application. This paper gives an overview of various helicon configurations, experimental observations, and modeling results with an emphasis on high density operation using light ion species. Axial variations in the plasma parameters are also shown to play an important role in understanding the behavior of the Mini-RFTF device at Oak Ridge National Laboratory. .

Carter, M. D.; Baity, F. W.; Goulding, R. H.; Jaeger, E. F.; Chang-Díaz, F. R.; Squire, J. P.

2001-10-01

417

Plasma membrane of Entamoeba histolytica  

PubMed Central

Axenically propagated Entamoeba histolytica (HK9:NIH strain) were employed as starting material for the isoation of plasma membrane by a novel procedure. In the absence of known enzymatic markers, the externally disposed polypeptides of intact amoebae were iodinated and the incorporated label used to monitor membrane separation and recovery. 12 major plasma membrane polypeptides (12 x 10(3)-200 x 10(3) mol wt) were labeled and separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Each of these was a glycoprotein. Preincubation of amoebae with concanavalin A stabilized the plasma membranes as large sheets, facilitating its separation by low-speed centrifugation. Dissociation of the lectin with alpha-methyl mannoside, followed by additional homogenization led to vesiculation and further purification. The isolated plasma membrane was recovered in high yield (28%) and enriched 30-fold in terms of incorporated iodide. All iodinated surface glycoproteins of the intact organism were present in the plasma membrane fraction. A Ca++-dependent ATPase was enriched in the plasma membrane to a similar extent, but over one-half of the total activity was associated with internal, unlabeled membranes, suggesting a dual localization of this activity. The isolated plasma membrane was enriched in cholesterol and had a cholesterol:molar ratio of 0.87. It also contained larger amounts of an unusual phospholipid--ceramide aminoethyl phosphonate--a phospholipase-resistant species.

1980-01-01

418

Atmospheric-pressure plasma jet  

DOEpatents

Atmospheric-pressure plasma jet. A .gamma.-mode, resonant-cavity plasma discharge that can be operated at atmospheric pressure and near room temperature using 13.56 MHz rf power is described. Unlike plasma torches, the discharge produces a gas-phase effluent no hotter than 250.degree. C. at an applied power of about 300 W, and shows distinct non-thermal characteristics. In the simplest design, two concentric cylindrical electrodes are employed to generate a plasma in the annular region therebetween. A "jet" of long-lived metastable and reactive species that are capable of rapidly cleaning or etching metals and other materials is generated which extends up to 8 in. beyond the open end of the electrodes. Films and coatings may also be removed by these species. Arcing is prevented in the apparatus by using gas mixtures containing He, which limits ionization, by using high flow velocities, and by properly shaping the rf-powered electrode. Because of the atmospheric pressure operation, no ions survive for a sufficiently long distance beyond the active plasma discharge to bombard a workpiece, unlike low-pressure plasma sources and conventional plasma processing methods.

Selwyn, Gary S. (Los Alamos, NM)

1999-01-01

419

Stable processing with unstable plasmas?  

NASA Astrophysics Data System (ADS)

Plasmas are employed for materials processing over a very wide range of conditions. For typical etch applications, these include plasmas generated in various ways with RF at various frequencies and power levels ranging from 100W up to 10000W. Mixed gas chemistries are used, at pressures ranging from mTorr to Torr, with multiple, often electron-attaching species present in significant proportions. These complex conditions are typically produced in production reactors that are hardly optimal for diagnostic access, so this is not a recipe for a quiescent lab plasma that may be conveniently studied. Inevitably a range of plasma instabilities and other unstable conditions may be encountered, often without immediate detection, as one spans the operating space. These unstable conditions may range from internal well known linear and quasi-linear plasma instabilities1, 2 to gross non-linear relaxation oscillations3, 4, 5, parametric drifts and even plasma extinguishment. Many of these phenomena involve strong interactions with the materials being processed and the external hardware that supports the reactor module operation. We will discuss certain questions: how may one observe such conditions (if you can't see it, does it matter from the processing perspective?); is it advisable to continue processing regardless; what might the consequences be, good or bad, and how they may be controlled6? 1) T. H. Stix, Waves in Plasmas, American Institute of Physics, New York (1992), and The Theory of Plasma Waves, McGraw-Hill (1962). 2) N. Krall and A. Trivelpiece, Principles of Plasma Physics, McGraw-Hill (1973). 3) M. Tuszewski, J. App. Phys., 79 8967 (1996) 4) M. A. Lieberman et. al., Appl. Phys. Lett. 75, 3617 (1999) 5) A. M. Marakhtanov et..al., J. Vac. Sci. Tech. A, 21 1864 (2003) and references therein. 6) D.L.Goodman and N. M. P. Benjamin, J. Phys. D, 36 2845 (2003).

Benjamin, Neil

2004-09-01

420

Effect of plasma surface interactions on PLT plasma parameters  

SciTech Connect

This paper gives a brief description of the geometry and parameters of the PLT tokamak, reviews some of the last four years' results that are particularly relevant to plasma-boundary interactions, and then concentrates on two specific problems.

Meservey, E.B.; Arunasalam, V.; Barnes, C.

1980-07-01

421

Plasma acceleration processes in an ablative pulsed plasma thruster  

SciTech Connect

Plasma acceleration processes in an ablative pulsed plasma thruster (APPT) were investigated. APPTs are space propulsion options suitable for microspacecraft, and have recently attracted much attention because of their low electric power requirements and simple, compact propellant system. The plasma acceleration mechanism, however, has not been well understood. In the present work, emission spectroscopy, high speed photography, and magnetic field measurements are conducted inside the electrode channel of an APPT with rectangular geometry. The successive images of neutral particles and ions give us a comprehensive understanding of their behavior under electromagnetic acceleration. The magnetic field profile clarifies the location where the electromagnetic force takes effect. As a result, it is shown that high density, ablated neutral gas stays near the propellant surface, and only a fraction of the neutrals is converted into plasma and electromagnetically accelerated, leaving the residual neutrals behind.

Koizumi, Hiroyuki; Noji, Ryosuke; Komurasaki, Kimiya; Arakawa, Yoshihiro [Department of Aeronautics and Astronautics, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Department of Advanced Energy, University of Tokyo, 5-1-5, Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Department of Aeronautics and Astronautics, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

2007-03-15

422

The Absence of Plasma in"Spark Plasma Sintering"  

SciTech Connect

Spark plasma sintering (SPS) is a remarkable method for synthesizing and consolidating a large variety of both novel and traditional materials. The process typically uses moderate uni-axial pressures (<100 MPa) in conjunction with a pulsing on-off DC current during operation. There are a number of mechanisms proposed to account for the enhanced sintering abilities of the SPS process. Of these mechanisms, the one most commonly put forth and the one that draws the most controversy involves the presence of momentary plasma generated between particles. This study employees three separate experimental methods in an attempt to determine the presence or absence of plasma during SPS. The methods employed include: in-situ atomic emission spectroscopy, direct visual observation and ultra-fast in-situ voltage measurements. It was found using these experimental techniques that no plasma is present during the SPS process. This result was confirmed using several different powders across a wide spectrum of SPS conditions.

Hulbert, Dustin M.; Anders, Andre; Dudina, Dina V.; Andersson, Joakim; Jiang, Dongtao; Unuvar, Cosan; Anselmi-Tamburini, Umberto; Lavernia, Enrique J.; Mukherjee, Amiya K.

2008-04-10

423

Liquid injection plasma deposition method and apparatus  

DOEpatents

A liquid injection plasma torch deposition apparatus for depositing material onto a surface of a substrate may comprise a plasma torch for producing a jet of plasma from an outlet nozzle. A plasma confinement tube having an inlet end and an outlet end and a central bore therethrough is aligned with the outlet nozzle of the plasma torch so that the plasma jet is directed into the inlet end of the plasma confinement tube and emerges from the outlet end of the plasma confinement tube. The plasma confinement tube also includes an injection port transverse to the central bore. A liquid injection device connected to the injection port of the plasma confinement tube injects a liquid reactant mixture containing the material to be deposited onto the surface of the substrate through the injection port and into the central bore of the plasma confinement tube.

Kong, Peter C. (Idaho Falls, ID); Watkins, Arthur D. (Idaho Falls, ID)

1999-01-01

424

Imaging Diagnostics in Dusty Plasmas  

NASA Astrophysics Data System (ADS)

The success of dusty plasmas is based on its unique diagnostic possibilities. The ability to follow the motion of any particle in a dusty plasma allows to explore the fundamental properties of strongly coupled systems at the kinetic level (see Chap. 7). This chapter gives an introduction to imaging diagnostics in dusty plasmas. In the first part, the basics of video microscopy are reviewed and the important role of a careful image analysis is stressed. The second part reports on recent developments on three-dimensional (3D) imaging techniques, that is, diagnostic systems which are able to track simultaneously all particles in a 3D dust cloud.

Block, Dietmar; Melzer, André

425

Plasma torque and nonambipolar transport  

SciTech Connect

Poloidal symmetry breaking in toroidal plasmas causes a damping of poloidal rotation and toroidal symmetry breaking a damping of toroidal rotation. These torques are transmitted by the magnetic field to the outside world. An upper limit exists on the torque that can be transmitted by magnetic asymmetries. This limit is enforced by shielding asymmetries from the plasma, which can be an important effect for toroidal asymmetries. The torque interaction of plasmas with magnetic fields can be either through an anisotropic pressure or by the drive for magnetic islands. The physics of both types of interactions are considered and paradoxical effects are clarified.

Boozer, Allen H. [Columbia University, New York, New York 10027 (United States)

2009-05-15

426

Resonant Excitation of Plasma Wakefields  

SciTech Connect

We describe characteristics of the bunch train and plasma source used in a resonant plasma wakefield experiment at the Brookhaven National Laboratory Accelerator Test Facility. The bunch train has the proper correlated spread to unambiguously observe the expected energy gain by the witness bunch at resonance. The plasma density in the capillary discharge is sufficiently high to reach the resonance with the typical bunch train spacing of this experiment. It is also uniform over more than 3/4 of the 2 cm-long capillary.

Muggli, P.; Allen, B. [University of Southern California, Los Angeles, CA 90089 (United States); Yakimenko, V.; Fedurin, M.; Kusche, K.; Babzien, M. [Brookhaven National Laboratory, Upton, NY 11973 (United States)

2010-11-04

427

Diffusion coefficients for stellar plasmas  

NASA Astrophysics Data System (ADS)

The diffusion coefficients of relatively dense plasmas that are typical of white dwarf envelopes are presently computed by means of an approximate method, based on the numerical evaluation of collision integrals for a screened Coulomb potential, which becomes rigorously valid in the limit of a dilute plasma. The plasmas encountered in white dwarf envelopes are noted to be neither weakly nor strongly coupled; a comparison with the results of rigorous Monte Carlo calculations applicable at very high densities indicates, however, that the region of intermediate coupling is probably reasonably bridged. Results are presented in the form of high accuracy analytic fits for the collision integrals.

Paquette, C.; Pelletier, C.; Fontaine, G.; Michaud, G.

1986-05-01

428

Plasma temperature measurements from highly ionized titanium imploding wire plasmas  

Microsoft Academic Search

Electron temperature measurements in highly ionized titanium plasmas are reported. The plasmas were created by imploding cylindrical arrays of fine wires with the Blackjack 5 pulse generator (peak diode voltage = 3.0 MV, peak current = 4.6 MA, and peak power = 10 TW at full operating level). Temperatures between 0.7 and 2.3 keV were obtained from the slope of

M. Gersten; J. E. Rauch; W. Clark; R. D. Richardson; G. M. Wilkinson

1981-01-01

429

Plasma temperature measurements from highly ionized titanium imploding wire plasmas  

Microsoft Academic Search

Electron temperature measurements in highly ionized titanium plasmas are reported. The plasmas were created by imploding cylindrical arrays of fine wires with the Blackjack 5 pulse generator (Peak diode voltage≊3.0 MV, peak current≊4.6 MA, peak power ≊10 TW at full operating level). Temperatures between 0.7 and 2.3 keV were obtained from the slope of the free-bound continuum. The results of

M. Gersten; J. E. Rauch; W. Clark; R. D. Richardson; G. M Wilkinson

1981-01-01

430

Influence of Plasma Instabilities in Ceramic Suspension Plasma Spraying  

Microsoft Academic Search

Direct current Suspension Plasma Spraying (SPS) allows depositing finely structured coatings. This article presents an analysis\\u000a of the influence of plasma instabilities on the yttria-stabilized suspension drops fragmentation. A particular attention is\\u000a paid to the treatment of suspension jet or drops according to the importance of voltage fluctuations (linked to those of the\\u000a arc root) and depending on the different

R. Etchart-Salas; V. Rat; J. F. Coudert; P. Fauchais; N. Caron; K. Wittman; S. Alexandre

2007-01-01

431

Space-plasma campaign on UCLA's Large Plasma Device (LAPD)  

NASA Astrophysics Data System (ADS)

Knudsen [JGR, 1996] describes a potential role for stationary Alfvén (StA) waves in auroral arcs' frequency dependence. Magnetized plasmas are predicted to support electromagnetic perturbations that are static in a fixed frame if there is uniform background plasma convection. These stationary waves should not be confused with standing waves that oscillate in time with a fixed, spatially varying envelope. Stationary waves have no time variation in the fixed frame. In the drifting frame, there is an apparent time dependence as plasma convects past fixed electromagnetic structures. We describe early results from an experimental campaign to reproduce in the lab the basic conditions necessary for the creation of StA waves, namely quasi-steady-state convection across magnetic field-aligned current channels. We show that an off-axis, fixed channel of electron current (and depleted density) is created in the Large Plasma Device Upgrade (LAPD) at UCLA, using a small, heated, oxide-coated electrode at one plasma-column end and we show that the larger plasma column rotates about its cylindrical axis from a radial electric field imposed by a special termination electrode on the same end. Initial experimentation with plasma-rotation-inducing termination electrodes began in May 2006 in the West Virginia Q Machine, leading to two designs that, in January 2007, were tested in LAPD. The radial profile of azimuthal velocity was consistent with predictions of rigid-body rotation. Current-channel experiments in LAPD, in August 2006, showed that inertial Alfvén waves could be concentrated in an off-axis channel of electron current and depleted plasma density. These experimental results will be presented and discussed. This research is supported by DOE and NSF.

Koepke, M. E.; Finnegan, S. M.; Knudsen, D. J.; Vincena, S.

2007-05-01

432

Plasma interactions with mixed-material plasma facing components  

NASA Astrophysics Data System (ADS)

Faced with ever more demanding technological requirements of plasma confinement devices, design efforts have moved toward using differing materials in various locations in the device. These designs have introduced new questions on the way these multiple materials will interact in a plasma environment and form mixed-materials. The linear plasma simulator, PISCES-B, is investigating the formation conditions, as well as the interactions, of mixed-materials in a plasma. This work focuses on the binary system of beryllium and carbon. Both the effects of carbon being deposited on a beryllium substrate and beryllium deposited on a carbon surface are investigated. At elevated exposure temperature (>500C) beryllium carbide can form and influence the erosion and hydrogen isotope retention properties of the material. The growth rate of the mixed-material layers are measured and compared to simple models under different plasma conditions. Critical parameters are the plasma impurity concentration, surface temperature and incident ion energy. *Work supported under DOE grant DE-FG03-95ER-54301.

Doerner, R. P.; Luckhardt, S.; Seraydarian, R.; Sze, F. C.; Whyte, D. G.

1998-11-01

433

Wide-area uniform plasma processing in an ECR plasma  

NASA Astrophysics Data System (ADS)

Large-area uniform material processing is demonstrated in reactive plasmas produced by a plane antenna with permanent magnets for the electron-cyclotron resonance at 2.45 GHz. Oxygen 0963-0252/5/2/027/img7 plasmas are used for the ashing of photoresist films; sulphur hexafluoride 0963-0252/5/2/027/img8 and carbon tetrafluoride 0963-0252/5/2/027/img9 are used for the etching of polysilicon and silicon dioxide films, respectively. In both cases the plasma parameters are measured in detail. Typically, the electron density in 0963-0252/5/2/027/img10 and 0963-0252/5/2/027/img11 plasmas is about (1 - 2) 0963-0252/5/2/027/img12 and the electron temperature is about 3 eV for a microwave power of 600 W. However, 0963-0252/5/2/027/img13 in the 0963-0252/5/2/027/img14 plasma. The ashing and etching rates for photoresist and polysilicon are 40 - 50 0963-0252/5/2/027/img15 and the etching rate of silicon dioxide is about 10 0963-0252/5/2/027/img15 in the uniform plasma region (z = 25 - 35 cm), when the microwave power is 600 W under the condition of the floating substrate potential. A quite homogeneous material processing of those films is established over a diameter of 40 - 45 cm at the distance of 25 - 35 cm from the antenna.

Hiyama, Shin; Ono, Takashi; Iizuka, Satoru; Sato, Noriyoshi

1996-05-01

434

Positron driven plasma wakefields  

NASA Astrophysics Data System (ADS)

The LHC is producing high-energy, high-charge proton bunches (1e11 protons at 1-7 TeV each) that could be used to accelerate ``witness'' electron bunches to TeV range eneregies via a plasma wakefield accelerator (PWFA). Simulations [1] suggest that a proton ``drive'' bunch is able to excite large wakefields if the bunch size is on the order of 100 ?m; however, the LHC paramters are currently on the 1 cm scale. SLAC'S FACET is able to supply positorn bunchs with the ideal parameters for driving a PWFA. Although at lower energy (2e10 positrons at 23 GeV each), initial simiulations in QuickPIC show that the physics of a positron drive bunch is very similar to that of a proton drive bunch. Differences in the physics arise from the mass difference: slower dephasing but faster transverse bunch evolution. Other considerations include driver head erosion and purity of the wakefield ion column. The physics of positive drivers for PWFA and the viability of this scheme for future high-energy colliders will be investigated at SLAC's FACET.[4pt] [1] Caldwell, et al. Nature Physics 5, 363 (2009).[0pt] [2] C.H. Huang, et al., J. Comp. Phys., 217(2), 658, (2006).

Pinkerton, S.; Shi, Y.; Huang, C.; An, W.; Mori, W. B.; Muggli, P.

2010-11-01

435

TFTR plasma regimes  

SciTech Connect

Significant extensions in the TFTR plasma operating regimes have been achieved with additional heating-system capability, installation of a multishot pellet injector, and the development of an enhanced confinement regime. In ohmically heated pellet-fueled discharges characterized by highly peaked density profiles, enhancements in tau/sub E/ have resulted in n/sub e/(0)tau/sub E/(a)-values of 1.5 x 10/sup 20/ m/sup -3/s. In neutral-beam-heated discharges, an operating regime has been developed in which substantial improvements in energy confinement time and neutron source strength are observed. Ion temperatures of approx.20 keV and n/sub e/(0)tau/sub E/(a)T/sub i/(0)-values of 2 x 10/sup 20/ m/sup -3/s keV have been achieved. This enhanced confinement regime is characterized by high values of ..beta../sub p/ and low values of collisionality. The observed surface voltage, which is negative during beam injection, is compared with models including beam-driven and bootstrap currents.

Hawryluk, R.J.; Arunasalam, V.; Bell, M.G.; Bitter, M. Blanchard, W.R.; Bretz, N.L.; Budny, R.; Bush, C.E.; Callen, J.D. Cohen, S.A.

1987-02-01

436

Plasma inverse transition acceleration  

SciTech Connect

It can be proved fundamentally from the reciprocity theorem with which the electromagnetism is endowed that corresponding to each spontaneous process of radiation by a charged particle there is an inverse process which defines a unique acceleration mechanism, from Cherenkov radiation to inverse Cherenkov acceleration (ICA) [1], from Smith-Purcell radiation to inverse Smith-Purcell acceleration (ISPA) [2], and from undulator radiation to inverse undulator acceleration (IUA) [3]. There is no exception. Yet, for nearly 30 years after each of the aforementioned inverse processes has been clarified for laser acceleration, inverse transition acceleration (ITA), despite speculation [4], has remained the least understood, and above all, no practical implementation of ITA has been found, until now. Unlike all its counterparts in which phase synchronism is established one way or the other such that a particle can continuously gain energy from an acceleration wave, the ITA to be discussed here, termed plasma inverse transition acceleration (PITA), operates under fundamentally different principle. As a result, the discovery of PITA has been delayed for decades, waiting for a conceptual breakthrough in accelerator physics: the principle of alternating gradient acceleration [5, 6, 7, 8, 9, 10]. In fact, PITA was invented [7, 8] as one of several realizations of the new principle.

Xie, Ming

2001-06-18

437

Dynamic Potentials in Gyrotropic Plasmas.  

National Technical Information Service (NTIS)

Wave equations are derived for the scalar and vector potentials of guided electromagnetic waves propagating in a laterally bounded magnetized plasma along the axis of the static magnetic field. Solutions are given in the Coulomb and the Lorentz gauge. The...

V. Bevc

1969-01-01

438

Layered plasma polymer composite membranes  

DOEpatents

Layered plasma polymer composite fluid separation membranes are disclosed, which comprise alternating selective and permeable layers for a total of at least 2n layers, where n is [>=]2 and is the number of selective layers. 2 figs.

Babcock, W.C.

1994-10-11

439

Vircator Operation at Plasma Assistance  

NASA Astrophysics Data System (ADS)

The influence of plasma on the processes of virtual cathode (VC) formation, high frequency (HF) generation, and plasma ions acceleration were studied. The theoretical consideration of the problem was analytically undertaken in one-dimensional approximation, that has shown the principal ability of low frequency (LF) oscillations of VC potential well and ion flow due to the periodic space charge neutralization by plasma ions. The experiments were carried out at the pulsed electron accelerator ``AGAT'', which is a microsecond diode with a magnetic insulation. The accelerator produced an annular relativistic electron beam (REB). Plasma was produced by the beam electrons. It was observed that relaxing VC with low frequency modulation of 20 MHz was formed. The current of REB was temporary modulated at this frequency. The temporal modulation of intense REB is now proposed for excitation of slow space charge wave when further REB is being spatially modulated by periodic magnetic field. It constructs the scheme of the collective ion accelerator.

Balakirev, V. A.; Magda, I. I.; Onishchenko, I. N.; Pushkarev, S. S.

2002-12-01

440

Beam and Plasma Physics Research.  

National Technical Information Service (NTIS)

Analysis was performed in high power microwave computations and theory and high energy plasma computations and theory. The HPM computations concentrated on generation, sources and propagation. Major codes used were the particle-in-cell codes SOS and ISIS....

R. F. Stellingwerf R. E. Peterkin D. J. Sullivan

1990-01-01

441

Concurrent Plasma Position on Labeling  

Center for Biologics Evaluation and Research (CBER)

Text Version... Temperatures. -30°C. -25°C. -20°C. FVIII in cryoprecipitate (IU FVIII/l plasma). 464. 447. 476. ... Storage Freezing Temperature and Time of Storage. 32. ... More results from www.fda.gov/downloads/advisorycommittees/committeesmeetingmaterials

442

Heat Measurement during Plasma Electrolysis  

NASA Astrophysics Data System (ADS)

It is important to establish an accurate heat measurement system to confirm the excess heat from the cold fusion phenomenon. During plasma electrolysis, an accurate heat measurement is especially difficult, because the input power is large and it causes significant evaporation of electrolyte and heat loss to the environment from the body of the electrolytic cell. In this study, a flow calorimetry system has been developed for accurate measurement. The energy balance of plasma electrolysis was measured at 100-102%, and the current efficiency were from 115 to 122% during the plasma electrolysis in 0.3 mol/dm3 Na2CO3 light water solution. Clear excess output energy has not been observed. Excess gases of 15-22% generation beyond Faraday's law was confirmed. The excess gas generation might be due to a plasma reaction.

Iizumi, K.; Fujii, M.; Mitsushima, S.; Kamiya, N.; Ota, K.-I.

443

MHD stability of tokamak plasmas  

SciTech Connect

This paper will give an overview of the some of the methods which are used to simulate the ideal MHD properties of tokamak plasmas. A great deal of the research in this field is necessarily numerical and the substantial progress made during the past several years has roughly paralleled the continuing availability of more advanced supercomputers. These have become essential to accurately model the complex configurations necessary for achieving MHD stable reactor grade conditions. Appropriate tokamak MHD equilibria will be described. Then the stability properties is discussed in some detail, emphasizing the difficulties of obtaining stable high {beta} discharges in plasmas in which the current is mainly ohmically driven and thus demonstrating the need for tailoring the current and pressure profiles of the plasma away from the ohmic state. The outline of this paper will roughly follow the physics development to attain the second region of stability in the PBX-M device at The Princeton Plasmas Physics Laboratory.

Chance, M.S. Sun, Y.C.; Jardin, S.C.; Kessel, C.E.; Okabayashi, M.

1992-08-01

444

MHD stability of tokamak plasmas  

SciTech Connect

This paper will give an overview of the some of the methods which are used to simulate the ideal MHD properties of tokamak plasmas. A great deal of the research in this field is necessarily numerical and the substantial progress made during the past several years has roughly paralleled the continuing availability of more advanced supercomputers. These have become essential to accurately model the complex configurations necessary for achieving MHD stable reactor grade conditions. Appropriate tokamak MHD equilibria will be described. Then the stability properties is discussed in some detail, emphasizing the difficulties of obtaining stable high {beta} discharges in plasmas in which the current is mainly ohmically driven and thus demonstrating the need for tailoring the current and pressure profiles of the plasma away from the ohmic state. The outline of this paper will roughly follow the physics development to attain the second region of stability in the PBX-M device at The Princeton Plasmas Physics Laboratory.

Chance, M.S. Sun, Y.C.; Jardin, S.C.; Kessel, C.E.; Okabayashi, M.

1992-01-01

445

Large amplitude relativistic plasma waves  

NASA Astrophysics Data System (ADS)

Relativistic, longitudinal plasma oscillations are studied for the case of a simple water bag distribution of electrons having cylindrical symmetry in momentum space with the axis of the cylinder parallel to the velocity of wave propagation. The plasma is required to obey the relativistic Vlasov-Poisson equations, and solutions are sought in the wave frame. An exact solution for the plasma density as a function of the electrostatic field is derived. The maximum electric field is presented in terms of an integral over the known density. It is shown that when the perpendicular momentum is neglected, the maximum electric field approaches infinity as the wave phase velocity approaches the speed of light. It is also shown that for any nonzero perpendicular momentum, the maximum electric field will remain finite as the wave phase velocity approaches the speed of light. The relationship to previously published solutions is discussed as is some recent controversy regarding the proper modeling of large amplitude relativistic plasma waves.

Coffey, Timothy

2010-05-01

446

Thermographic Look at Plasma Spraying.  

National Technical Information Service (NTIS)

Plasma spray systems are used to deposit high temperature materials on substrates to form coatings. Thermal analysis of these systems will assist in determining spray parameters for different materials. Infrared videothermography was used to measure tempe...

M. D. Kelly L. D. Abney

1985-01-01

447

Configuration studies of LHD plasmas.  

National Technical Information Service (NTIS)

Configuration studies are performed on the plasmas of The Large Helical Device (LHD), the construction of which is almost completed at the National Institute for Fusion Science. The LHD has flexibility as an experimental device and can have various config...

M. Okamoto

1997-01-01

448

Quasilinear Diffusion in Inhomogeneous Plasmas.  

National Technical Information Service (NTIS)

The problem of inhomogeneous diffusion in a plasma is considered with emphasis on its possible application to relativistic electron beams. A one-dimensional model with a background electrostatic field is used to illustrate the basic approach, which is the...

D. L. Hooley

1975-01-01

449

Conductivity of a relativistic plasma  

SciTech Connect

The collision operator for a relativistic plasma is reformulated in terms of an expansion in spherical harmonics. This formulation is used to calculate the electrical conductivity. 13 refs., 1 fig., 1 tab.

Braams, B.J.; Karney, C.F.F.

1989-03-01

450

Interplanetary medium A dusty plasma  

NASA Astrophysics Data System (ADS)

The average mass of dust per volume in space equals that of the solar wind so that the interplanetary medium should provide an obvious region to study dust plasma interactions. While dust collective behavior is typically not observed in the interplanetary medium, the dust component rather consists of isolated grains screened by and interacting with the plasma. Space measurements have revealed several phenomena possibly resulting from dust plasma interactions, but most of the dust plasma interactions are at present not quantified. Examples are the production of neutrals and pick-up ions from the dust, dust impact generated field variations at spacecraft and magnetic field variations possibly caused by solar wind interacting with dust trails. Since dust particles carry a surface charge, they are exposed to the Lorentz force in the interplanetary magnetic field and for grains of sub-micrometer sizes acceleration can be substantial.

Mann, Ingrid

451

RPC: The Rosetta Plasma Consortium  

NASA Astrophysics Data System (ADS)

The Rosetta Plasma Consortium (RPC) will make in-situ measurements of the plasma environment of comet 67P/Churyumov-Gerasimenko. The consortium will provide the complementary data sets necessary for an understanding of the plasma processes in the inner coma, and the structure and evolution of the coma with the increasing cometary activity. Five sensors have been selected to achieve this: the Ion and Electron Sensor (IES), the Ion Composition Analyser (ICA), the Langmuir Probe (LAP), the Mutual Impedance Probe (MIP) and the Magnetometer (MAG). The sensors interface to the spacecraft through the Plasma Interface Unit (PIU). The consortium approach allows for scientific, technical and operational coordination, and makes optimum use of the available mass and power resources.

Carr, C.; Cupido, E.; Lee, C. G. Y.; Balogh, A.; Beek, T.; Burch, J. L.; Dunford, C. N.; Eriksson, A. I.; Gill, R.; Glassmeier, K. H.; Goldstein, R.; Lagoutte, D.; Lundin, R.; Lundin, K.; Lybekk, B.; Michau, J. L.; Musmann, G.; Nilsson, H.; Pollock, C.; Richter, I.; Trotignon, J. G.

2007-02-01

452

Plasma fluoride and enamel fluorosis.  

PubMed

It is postulated that tissue fluid F concentrations are the primary determinants of flouride effects on bones and developing teeth and that these concentrations are dependent on, or mirrored by, blood plasma F. It has earlier been shown that the plasma F levels are dependent on the dietary F supply as well as on skeletal F concentration. Fasting and post-ingestion or postinjection plasma F levels have been determined in rats on F doses that cause different degrees of enamel fluorosis. The results indicate that temporary peak values rather than elevated fasting values are responsible for the occurrence of enamel fluorosis and that the peak values must approach about 10 muM in order to block enamel formation by the ameloblasts. The diagnostic and prognostic importance of plasma F determinations is discussed. PMID:1000344

Angmar-Månsson, B; Ericsson, Y; Ekberg, O

1976-11-24

453

Plasma Sound Source Basic Research.  

National Technical Information Service (NTIS)

This report investigates the phenomena of breakdown and initial arc formation of a plasma sound source. The prebreakdown phase is examined experimentally. A proton-hopping model is proposed that is qualitatively consistent with the data. A literature revi...

R. L. Rogers J. C. Espinosa D. L. Fisher A. M. Gleeson

1999-01-01

454

Laser Assisted Plasma Arc Welding  

SciTech Connect

Experiments have been performed using a coaxial end-effecter to combine a focused laser beam and a plasma arc. The device employs a hollow tungsten electrode, a focusing lens, and conventional plasma arc torch nozzles to co-locate the focused beam and arc on the workpiece. Plasma arc nozzles were selected to protect the electrode from laser generated metal vapor. The project goal is to develop an improved fusion welding process that exhibits both absorption robustness and deep penetration for small scale (< 1.5 mm thickness) applications. On aluminum alloys 6061 and 6111, the hybrid process has been shown to eliminate hot cracking in the fusion zone. Fusion zone dimensions for both stainless steel and aluminum were found to be wider than characteristic laser welds, and deeper than characteristic plasma arc welds.

FUERSCHBACH,PHILLIP W.

1999-10-05

455

Waves in Space Plasmas (WISP).  

National Technical Information Service (NTIS)

Activities under this project have included participation in the Waves in Space Plasmas (WISP) program, a study of the data processing requirements for WISP, and theoretical studies of radio sounding, ducting, and magnetoionic theory. An analysis of radio...

W. Calvert

1994-01-01

456

The beam driven plasma neutralizer  

NASA Astrophysics Data System (ADS)

The improvement of the efficiency of neutral beam systems to be compatible with the economic requirements of fusion power plants is a key theme in the European research programme. A novel plasma neutralizer, in which the negative ion beam itself is the source of the plasma, is described. Its success depends on the confinement of the free electrons generated by stripping from the beam and their generation of additional plasma. The device requires no additional power in contrast to the photoneutralizer, presently the main device of research interest. Although the efficiency of the plasma device is not as high as the photoneutralizer it is essentially of a low technological risk, inherently reliable and will not require a significant R&D programme to demonstrate.

Surrey, E.; Holmes, A.

2013-02-01

457

PLASMA HEATING AND CONFINING DEVICE  

DOEpatents

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)

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

1962-02-13

458

Layered plasma polymer composite membranes  

DOEpatents

Layered plasma polymer composite fluid separation membranes are disclosed, which comprise alternating selective and permeable layers for a total of at least 2n layers, where n is .gtoreq.2 and is the number of selective layers.

Babcock, Walter C. (Bend, OR)

1994-01-01

459

Laser Plasma Microthruster Performance Evaluation  

Microsoft Academic Search

The micro laser plasma thruster (?LPT) is a sub-kilogram thruster that is capable of meeting the Air Force requirements for the Attitude Control System on a 100-kg class small satellite. The ?LPT uses one or more 4W diode lasers to ablate a solid fuel, producing a jet of hot gas or plasma which creates thrust with a high thrust\\/power ratio.

James R. Luke; Claude R. Phipps

2003-01-01

460

Laser Plasma Microthruster Performance Evaluation  

Microsoft Academic Search

The micro laser plasma thruster (muLPT) is a sub-kilogram thruster that is capable of meeting the Air Force requirements for the Attitude Control System on a 100-kg class small satellite. The muLPT uses one or more 4W diode lasers to ablate a solid fuel, producing a jet of hot gas or plasma which creates thrust with a high thrust\\/power ratio.

James R. Luke; Claude R. Phipps

2003-01-01

461

Plasma duplex treatment of stellite  

Microsoft Academic Search

Despite their excellent tribological properties, the lifetime of stellites in some applications in metallurgical and mechanical engineering is not sufficient. This study describes the development of a duplex treatment for stellite 6B, which consists of either plasma nitriding (PN) or plasma nitrocarburizing (PNC), followed by the deposition of boron-containing hard coatings (TiBN or TiB2). The influence of the process parameters

C Pfohl; K.-T Rie

2001-01-01

462

Flavors in an expanding plasma  

SciTech Connect

We consider the effect of an expanding plasma on probe matter by determining time-dependent D7 embeddings in the holographic dual of an expanding viscous plasma. We calculate the chiral condensate and meson spectra including contributions of viscosity. The chiral condensate essentially confirms the expectation from the static black hole. For the meson spectra we propose a scheme that is in agreement with the adiabatic approximation. New contributions arise for the vector mesons at the order of the viscosity terms.

Grosse, Johannes; Janik, Romuald A.; Surowka, Piotr [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)

2008-03-15

463

Physics of space plasmas (1988)  

Microsoft Academic Search

Recent theoretical and observational investigations of space plasmas are discussed in reviews and reports. Topics addressed include the origins of weather in the high-latitude ionosphere, ionospheric plasma turbulence in the high-latitude E region, polar winds, coordinated observations of high-latitude turbulence, the polar cap with northward IMF, the formation of polar-cap arcs, and energetic atmospheric photoelectrons due to solar soft X-rays

Tom Chang; G. B. Crew; J. R. Jasperse

1989-01-01

464

Plastic Deformations in Complex Plasmas  

SciTech Connect

Complex plasmas are macroscopic model systems of real solids and liquids, used to study underdamped dynamics and wave phenomena. Plastic deformations of complex plasma crystals under slow uniaxial compression have been studied experimentally and numerically. It is shown that the lattice becomes locally sheared and that this strain is relaxed by shear slips resulting in global uniform compression and heat generation. Shear slips generate pairs of dislocations which move in opposite directions at subsonic speeds.

Durniak, C.; Samsonov, D. [Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool, L69 3GJ (United Kingdom)

2011-04-29

465

NADH oxidase of plasma membranes  

Microsoft Academic Search

NADH oxidase is a cyanide-resistant and hormone-responsive oxidase intrinsic to the plasma membrane of both plant and animal cells. The activity has many unique characteristics that distinguish it from other oxidases and oxidoreductases of both organelles and internal membranes and from other oxidoreductases of the plasma membrane. Among these are resistance to inhibition by cyanide, catalase, superoxide dismutase, and phenylchloromer-curibenzoate.

D. James Morré; Andrew O. Brightman

1991-01-01

466

Atmospheric pressure plasma jet applications  

Microsoft Academic Search

Summary form only given. The atmospheric pressure plasma jet (APPJ) is a non-thermal, high pressure plasma discharge that produces a high velocity effluent stream of highly reactive chemical species. The discharge operates on a feedstock gas (e.g. He\\/O2\\/H2 O) which flows between two concentric cylindrical electrodes: an outer grounded electrode and an inner electrode powered at 13.56 MHz RF. While

H. W. Herrmann; L. Henins; G. S. Selwyn

1998-01-01

467

Chaos in a complex plasma  

SciTech Connect

Chaotic dynamics is observed experimentally in a complex (dusty) plasma of three particles. A low-frequency sinusoidal modulation of the plasma density excites both the center-of-mass and breathing modes. Low-dimensional chaos is seen for a 1:2 resonance between these modes. A strange attractor with a dimension of 2.48{+-}0.05 is observed. The largest Lyapunov exponent is positive.

Sheridan, T.E. [Department of Physics and Astronomy, Ohio Northern University, Ada, Ohio 45810 (United States)

2005-08-15

468

Cholecystokinin elevates mouse plasma lipids.  

PubMed

Cholecystokinin (CCK) is a peptide hormone that induces bile release into the intestinal lumen which in turn aids in fat digestion and absorption in the intestine. While excretion of bile acids and cholesterol into the feces eliminates cholesterol from the body, this report examined the effect of CCK on increasing plasma cholesterol and triglycerides in mice. Our data demonstrated that intravenous injection of [Thr28, Nle31]-CCK at a dose of 50 ng/kg significantly increased plasma triglyceride and cholesterol levels by 22 and 31%, respectively, in fasting low-density lipoprotein receptor knockout (LDLR(-/-)) mice. The same dose of [Thr28, Nle31]-CCK induced 6 and 13% increases in plasma triglyceride and cholesterol, respectively, in wild-type mice. However, these particular before and after CCK treatment values did not achieve statistical significance. Oral feeding of olive oil further elevated plasma triglycerides, but did not alter plasma cholesterol levels in CCK-treated mice. The increased plasma cholesterol in CCK-treated mice was distributed in very-low, low and high density lipoproteins (VLDL, LDL and HDL) with less of an increase in HDL. Correspondingly, the plasma apolipoprotein (apo) B48, B100, apoE and apoAI levels were significantly higher in the CCK-treated mice than in untreated control mice. Ligation of the bile duct, blocking CCK receptors with proglumide or inhibition of Niemann-Pick C1 Like 1 transporter with ezetimibe reduced the hypercholesterolemic effect of [Thr28, Nle31]-CCK in LDLR(-/-) mice. These findings suggest that CCK-increased plasma cholesterol and triglycerides as a result of the reabsorption of biliary lipids from the intestine. PMID:23300532

Zhou, Lichun; Yang, Hong; Lin, Xinghua; Okoro, Emmanuel U; Guo, Zhongmao

2012-12-21

469

Plasma treatment for fluxless soldering  

Microsoft Academic Search

Plasma treatment of printed circuit boards (PCB) with solid solder deposits (SSD) makes it possible to eliminate the application of conventional flux in reflow soldering process. This work deals with the dependence of surface modification of eutectic SnPb solder materials on gas pressure and gas flowrate of the CF4\\/air (10:1) gas mixture in the reactor. After plasma treatment, both metal

R. Deltschew; D. Hirsch; H. Neumann; T. Herzog; K. J. Wolter; M. Nowottnick; K. Wittke

2001-01-01