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Sep 2004

Volume 11, Issue 9, pp. L45-L56, 4167-4539

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Collisional transport in a low aspect ratio tokamak

D. A. Gates, H. E. Mynick, and R. B. White

Phys. Plasmas 11, L45 (2004); http://dx.doi.org/10.1063/1.1781165 (4 pages) | Cited 5 times

Online Publication Date: 2 August 2004

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Calculations of collisional diffusivities in toroidal magnetic plasma confinement devices order the toroidal gyroradius to be small relative to the poloidal gyroradius, i.e., ρiϕρiθ, where ρiϕ ≡ mivthi/qBϕ and ρiθ ≡ mivthi/qBθ. This ordering is central to what is usually referred to as neoclassical transport theory. This ordering is incorrect at low aspect ratio (with aspect ratio A ≡ R/a, where R is the major radius of the torus and a is the minor radius), where it can be the case that ρiϕ>ρiθ. The correction to the test particle diffusivities is numerically calculated by comparing the diffusivities as determined by a full orbit code (which we refer to as omniclassical diffusion) with those from a gyroaveraged orbit code (neoclassical diffusion), and then corroborated by an analytic calculation. The omniclassical diffusion can be up to 2.5 times the calculated neoclassical value. The implications of this work for the analysis of collisional transport in low aspect ratio devices are discussed.
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52.25.Fi Transport properties
52.20.Dq Particle orbits
52.55.Fa Tokamaks, spherical tokamaks
52.65.Cc Particle orbit and trajectory

Properties of fluid deuterium under double-shock compression to several Mbar

T. R. Boehly, D. G. Hicks, P. M. Celliers, T. J. B. Collins, R. Earley, J. H. Eggert, D. Jacobs-Perkins, S. J. Moon, E. Vianello, D. D. Meyerhofer, and G. W. Collins

Phys. Plasmas 11, L49 (2004); http://dx.doi.org/10.1063/1.1778164 (4 pages) | Cited 29 times

Online Publication Date: 18 August 2004

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The compressibility of fluid deuterium up to several Mbar has been probed using laser-driven shock waves reflected from a quartz anvil. Combining high-precision ( ∼ 1%) shock velocity measurements with the double-shock technique, where differences in equation of state (EOS) models are magnified, has allowed better discrimination between theoretical predictions in the second-shock regime. Double-shock results are in agreement with the stiffer EOS models—which exhibit roughly fourfold single-shock compression—for initial shocks up to 1 Mbar and above 2 Mbar, but diverge from these predictions in between. Softer EOS models—which exhibit sixfold single-shock compression at 1 Mbar—overestimate the reshock pressure for the entire range under study.
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62.50.-p High-pressure effects in solids and liquids
64.30.-t Equations of state of specific substances

Criteria for second stability for ballooning modes in stellarators

S. R. Hudson and C. C. Hegna

Phys. Plasmas 11, L53 (2004); http://dx.doi.org/10.1063/1.1779227 (4 pages) | Cited 1 time

Online Publication Date: 26 August 2004

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An expression determining how variations in the pressure gradient and average magnetic shear affect ballooning stability for a stellarator equilibrium is presented. The procedure for determining the marginal stability boundaries, for each field line, depends only on the equilibrium and a single ballooning eigenfunction calculation. This information is sufficient to determine if increasing pressure gradient is stabilizing or destabilizing and to predict whether the configuration possesses a second stable region.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.25.-b Plasma properties
52.55.Jd Magnetic mirrors, gas dynamic traps
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back to top Basic Plasma Phenomena, Waves, Instabilities

Quantum collective approach to the thermodynamic properties of degenerate plasma

A. H. Khalfaoui, D. Bennaceur-Doumaz, and L. Saoudi

Phys. Plasmas 11, 4167 (2004); http://dx.doi.org/10.1063/1.1773172 (11 pages) | Cited 1 time

Online Publication Date: 29 July 2004

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Thermodynamic functions of a system of partially degenerate electrons and strongly coupled ions are derived from first principles. A quantum collective approach is developed to analyze nonidealities inherent to very high density plasma. The model considers the electron oscillations (plasmons) and ion oscillations (ion sound waves) as quasiparticles sharing the energy of the system. Statistical thermodynamic calculations lead to simple, analytical expressions for internal energy as well as an equation of state. A dispersion relation for the high frequency branch is introduced to take into account the partial degeneracy state and thereby to quantify temperature finiteness effect on thermodynamic properties of very dense plasma. The present results are in good quantitative agreement with the existing models and represent a significant improvement over previous calculations which are based mainly on numerical experiments. More physical insight is explicitly stated presently which makes a contribution to the theoretical knowledge of coupled degenerate plasma for thermonuclear fusion as well as of astrophysical interests.
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52.25.Kn Thermodynamics of plasmas
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Dm Sound waves
back to top Nonlinear Phenomena, Turbulence, Transport

Absolute and convective instabilities of parallel propagating circularly polarized Alfvén waves: Decay instability

M. S. Ruderman and D. Simpson

Phys. Plasmas 11, 4178 (2004); http://dx.doi.org/10.1063/1.1774166 (10 pages) | Cited 5 times

Online Publication Date: 29 July 2004

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The absolute and convective instabilities of circularly polarized Alfvén waves propagating along an ambient magnetic field are studied. The approximation of ideal magnetohydrodynamics is used. The analysis is restricted to the decay instability that occurs when the sound speed is smaller than the Alfvén speed. In addition, it is assumed that the amplitude a of an unstable Alfvén wave (pump wave) is small. This assumption allows us to study the problem analytically using expansions in power series with respect to a. It is shown that there are quantities, Ul<0 and Ur>0, such that the pump wave is absolutely unstable in a reference frame moving with velocity U with respect to the rest plasma if Ul<U<Ur. If either U<Ul or U>Ur, then the pump wave is convectively unstable. The expressions for Ul and Ur are found. The signaling problem is studied in a reference frame where the pump wave is convectively unstable. It is shown that spatially amplifying waves exist only when the signaling frequency is in two narrow symmetric frequency bands with the widths of the order of a. The implication of the obtained results on the interpretation of observational data obtained in space missions is discussed. It is shown that circularly polarized Alfvén waves propagating in the solar wind are convectively unstable in a reference frame of any spacecraft moving with the velocity not exceeding a few tens of km∕s in the solar reference frame. The spatial amplification scale of these waves is very large, of the order of 1/6 a.u. In view of these results it is not surprising at all that evidence of the decay instability of Alfvén waves in the solar wind is sparse.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
95.30.Qd Magnetohydrodynamics and plasmas
52.72.+v Laboratory studies of space- and astrophysical-plasma processes
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
96.20.Br Origin and evolution
back to top Ionospheric, Solar-system, and Astrophysical Plasmas

Electrostatic perturbations in partially ionized plasma with the effects of ionization and recombination

J. Vranjes, M. Y. Tanaka, M. Kono, and S. Poedts

Phys. Plasmas 11, 4188 (2004); http://dx.doi.org/10.1063/1.1775803 (8 pages) | Cited 6 times

Online Publication Date: 29 July 2004

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The behavior of the electrostatic ion acoustic mode in a partially ionized plasma is studied in the presence of collisions which involve processes of ionization and recombination, taking into account the dynamics of the neutrals caused by elastic and inelastic collisions with ions. The application of the model to space plasmas, which are usually subject to gravity, is discussed in detail. A dispersion equation which includes the effects of ionization and recombination is derived and the stability/instability conditions are discussed. Parameters applicable to a region of the upper solar chromosphere are used and the increment of the ion sound wave is calculated yielding an unstable ion sound wave for wavelengths larger than 20 km.
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52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Dm Sound waves
52.25.Ya Neutrals in plasmas
52.25.Jm Ionization of plasmas
back to top Low-temperature Plasmas, Plasma Applications, Plasma Sources, Sheaths

Characterization of the resonant electromagnetic mode in helicon discharges

Martin I. Panevsky and Roger D. Bengtson

Phys. Plasmas 11, 4196 (2004); http://dx.doi.org/10.1063/1.1773552 (10 pages) | Cited 9 times

Online Publication Date: 29 July 2004

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This paper presents experimental evidence for the existence of a resonant electromagnetic mode in a helicon plasma, and characterizes its resonant frequency, energy absorption rate, and contribution to the overall power balance. An experimental method developed to detect and characterize the plasma impedance is introduced. Power flow analysis shows that the resonant electromagnetic mode is the dominant mechanism driving helicon plasma discharges in cylindrical geometry. The weakly damped wavefields are absorbed in a short distance, indicating that the wavefields may be trapped in a potential well created by a density gradient.
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52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.80.-s Electric discharges
52.25.Fi Transport properties
52.70.-m Plasma diagnostic techniques and instrumentation
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
back to top Inertially Confined Plasmas, Dense Plasmas, Equations of State

Stimulated Raman scattering of a laser beam in a plasma with azimuthal magnetic field

Vivek Sajal and V. K. Tripathi

Phys. Plasmas 11, 4206 (2004); http://dx.doi.org/10.1063/1.1777238 (7 pages) | Cited 5 times

Online Publication Date: 4 August 2004

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A strong azimuthal magnetic field localizes the lower hybrid waves radially in laser produced plasmas. The laser pump parametrically excites a lower hybrid wave and a backscattered electromagnetic sideband wave. The density perturbation due to the lower hybrid wave couples with the oscillatory velocity of electrons due to the pump wave, to produce a nonlinear current driving the sideband. The pump and sideband waves exert a ponderomotive force on electrons driving the lower hybrid wave. The local effects reduce the growth rate of stimulated Raman scattering. The fundamental radial eigenmode (p = 0) of the lower hybrid wave is the maximally growing mode. The scattering process can be used as a diagnostic for the azimuthal magnetic field.
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52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.38.Bv Rayleigh scattering; stimulated Brillouin and Raman scattering
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.25.Fi Transport properties
back to top Low-temperature Plasmas, Plasma Applications, Plasma Sources, Sheaths

Effects of electron inertia in capacitively coupled radio frequency discharges

Nong Xiang

Phys. Plasmas 11, 4213 (2004); http://dx.doi.org/10.1063/1.1777241 (7 pages) | Cited 3 times

Online Publication Date: 4 August 2004

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The effects of the electron inertia on the plasma and sheath dynamics in capacitively coupled rf discharges with frequency ωωpi are investigated (here, ω and ωpi are the rf frequency and bulk ion plasma frequency, respectively). It is found that the effects of the electron inertia on the plasma density and ion velocity in the quasi-neutral region depend on the ratio of the amplitudes of the discharge current Irf and ion current IB = en0Cs (here, e is the unit charge, n0 is the plasma density at center, and Cs is the ion sound speed). If the ratio is small so that Irf/IBmath (here, mi and me are ion and electron masses, respectively), the ion and time-averaged electron densities, ion velocity, and electric fields are little affected by the electron inertia. Otherwise, the effects of the electron inertia are significant. It is also shown that the assumption that the electrons obey the Boltzmann distribution in the sheath is invalid when the electron flux flowing to the electrode is significant.
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52.80.Pi High-frequency and RF discharges
52.40.Kh Plasma sheaths
52.25.Fi Transport properties
back to top Nonlinear Phenomena, Turbulence, Transport

Relativistic quasilinear diffusion in axisymmetric magnetic geometry for arbitrary-frequency electromagnetic fluctuations

Alain J. Brizard and Anthony A. Chan

Phys. Plasmas 11, 4220 (2004); http://dx.doi.org/10.1063/1.1773554 (10 pages) | Cited 12 times

Online Publication Date: 6 August 2004

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A relativistic bounce-averaged quasilinear diffusion equation is derived to describe stochastic particle transport associated with arbitrary-frequency electromagnetic fluctuations in a nonuniform magnetized plasma. Expressions for the elements of a relativistic quasilinear diffusion tensor are calculated explicitly for magnetically trapped particle distributions in axisymmetric magnetic geometry in terms of gyro-drift-bounce wave-particle resonances. The resonances can destroy any one of the three invariants of the unperturbed guiding-center Hamiltonian dynamics.
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52.25.Fi Transport properties
52.25.Xz Magnetized plasmas
52.55.Lf Field-reversed configurations, rotamaks, astrons, ion rings, magnetized target fusion, and cusps
52.35.Kt Drift waves
52.25.Gj Fluctuation and chaos phenomena
52.27.Ny Relativistic plasmas
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
back to top Magnetically Confined Plasmas, Heating, Confinement

Stabilization of line tied resistive wall kink modes with rotating walls

C. C. Hegna

Phys. Plasmas 11, 4230 (2004); http://dx.doi.org/10.1063/1.1773777 (9 pages) | Cited 24 times

Online Publication Date: 9 August 2004

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A method suggested by Gimblett [ C. G. Gimblett, Plasma Phys. Controlled Fusion, 31 2183 (1989) ] for stabilizing resistive wall modes by using a rotating double wall configuration is applied to a line tied screw pinch equilibrium. The line tied boundary conditions provide an additional stabilizing mechanism relative to instabilities present in periodic cylinders that limits ideal kink instability to only be present when qa<1 for m = 1 modes. With differentially rotating walls, resistive wall modes can be stabilized with qa values less than unity. For a given equilibrium, there exists an optimal spacing between a stationary and a rotating wall that minimizes the critical wall rotation frequency for stabilization.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.55.Dy General theory and basic studies of plasma lifetime, particle and heat loss, energy balance, field structure, etc.
52.30.-q Plasma dynamics and flow
back to top Nonlinear Phenomena, Turbulence, Transport

Asymptotic freeze-out of the perturbations generated inside a corrugated rarefaction wave

J. G. Wouchuk and A. D. Serrano Rodrigo

Phys. Plasmas 11, 4239 (2004); http://dx.doi.org/10.1063/1.1775011 (10 pages)

Online Publication Date: 9 August 2004

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Based on previous work [J. G. Wouchuk and R. Carretero, Phys. Plasmas 10, 4237 (2003)], the conditions of asymptotic freeze-out of the ripples at the tail of a corrugated rarefaction wave are analyzed. The precise location of the freezing-out regions in the space of preshock parameters is tried, and an efficient algorithm for their determination is given. It is seen that asymptotic freeze-out can only happen for gases that have an isentropic exponent γ<γcr ≈ 2.2913…. It is shown that the late time freeze-out of the ripple perturbations is correlated to the initial tangential velocity profile (at t = 0+) inside the expansion fan.
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47.20.-k Flow instabilities
47.40.-x Compressible flows; shock waves
52.57.-z Laser inertial confinement
back to top Basic Plasma Phenomena, Waves, Instabilities

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

Christiane Schröder, Olaf Grulke, Thomas Klinger, and Volker Naulin

Phys. Plasmas 11, 4249 (2004); http://dx.doi.org/10.1063/1.1779225 (5 pages) | Cited 19 times

Online Publication Date: 13 August 2004

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In a cylindrical helicon plasma, mode structures of coherent drift waves are studied in the poloidal plane, the plane perpendicular to the ambient magnetic field. The mode structures rotate with a constant angular velocity in the direction of the electron diamagnetic drift and show significant radial bending. The experimental observations are compared with numerical solutions of a linear nonlocal cylindrical model for drift waves [Ellis et al., Plasma Phys. 22, 113 (1980)]. In the numerical model, a transition to bended mode structures is found if the plasma collisionality is increased. This finding proves that the experimentally observed bended mode structures are the result of high electron collisionality.
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52.35.Kt Drift waves
52.25.Xz Magnetized plasmas
52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
back to top Nonlinear Phenomena, Turbulence, Transport

Transport coefficients in relativistic collisionless plasmas

K. Bendib-Kalache, A. Bendib, and G. Matthieussent

Phys. Plasmas 11, 4254 (2004); http://dx.doi.org/10.1063/1.1782192 (7 pages)

Online Publication Date: 13 August 2004

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The computation of the relativistic transport coefficients in collisionless plasmas is presented. The stationary relativistic Vlasov equation is analytically solved for perturbed plasmas with respect to the global equilibrium defined by the Maxwell–Boltzmann–Jüttner distribution function. The explicit expression of the distribution function is derived and the generalized collisionless transport coefficients are deduced for arbitrary plasma temperature. It is found that the relativistic effects tend to increase the value of the transport coefficients. In particular, in ultrarelativistic regimes the temperature anisotropy reaches its maximum value.
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52.27.Ny Relativistic plasmas
52.25.Fi Transport properties
52.25.Dg Plasma kinetic equations
back to top Inertially Confined Plasmas, Dense Plasmas, Equations of State

Design of a 250 eV cryogenic ignition capsule for the National Ignition Facility

George L. Strobel, Steven W. Haan, David H. Munro, and Thomas R. Dittrich

Phys. Plasmas 11, 4261 (2004); http://dx.doi.org/10.1063/1.1774167 (6 pages) | Cited 5 times

Online Publication Date: 13 August 2004

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Optimized performance of a capsule intended to produce ignition on the National Ignition Facility [J. A. Paisner, J. D. Boyes, S. A. Kumpan, W. H. Lowdermilk, and M. S. Sorem, Laser Focus World 30, 75 (1994)] is presented. Performance is optimized, for a 250 eV isotropic drive on a beryllium(copper) ablator, by varying the ablator outside radius, ablator thickness, the concentration of copper dopant in the ablator, and the fuel thickness, while keeping the absorbed energy fixed. Dopant concentration is constrained to be uniform in the ablator. The drive shock timing is adjusted to produce a low entropy implosion for each set of dimensions. The absorbed energy is kept fixed at 190 kJ, which results in the ablator outside radius remaining practically constant, about 0.137 cm. For capsule geometry near that resulting in optimal implosion yield, the absorbed energy depends only slightly on the ablator or fuel thickness. The parameter space of capsule dimensions was searched for central vapor densities of 0.3 and 0.5 mg/cc. Despite the detailed optimization, it is found that the capsule is notably more unstable than comparable capsules with a graded dopant in the ablator, as reported in previous literature.
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28.52.Av Theory, design, and computerized simulation
28.52.Fa Materials
28.52.Cx Fueling, heating and ignition
52.57.-z Laser inertial confinement
back to top Magnetically Confined Plasmas, Heating, Confinement

Convective transport in the scrape-off-layer by nonthermalized spinning blobs

J. R. Myra, D. A. D’Ippolito, S. I. Krasheninnikov, and G. Q. Yu

Phys. Plasmas 11, 4267 (2004); http://dx.doi.org/10.1063/1.1774168 (8 pages) | Cited 25 times

Online Publication Date: 13 August 2004

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In this paper, two-dimensional blob models of convective transport in the scrape-off-layer (SOL) are generalized to include the internal temperature profile of the blob. This generalization provides a mechanism for blob internal spin and enables consideration of SOL energy transport. Solutions with aligned density and temperature contours satisfy the resulting “hot blob” equations and are considered here. It is shown that spin increases blob coherence, prevents the formation of extended radial streamers or fingers, reduces the radial convection velocity due to mixing and mitigation of the curvature-induced charge polarization, and provides a new mechanism for poloidal motion of the blob. Additionally, spinning blobs are shown to survive as coherent objects in the presence of weak externally sheared flows, and have blob speeds that depend on the sign of the spin relative to the external sheared flow. The work provides strong motivation for investigating the physics of parallel disconnected blobs, and the relationship of spin and disconnection physics to edge localized mode propagation and the density limit.
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52.25.Fi Transport properties
52.35.Ra Plasma turbulence
52.55.Dy General theory and basic studies of plasma lifetime, particle and heat loss, energy balance, field structure, etc.
52.55.Fa Tokamaks, spherical tokamaks
back to top Inertially Confined Plasmas, Dense Plasmas, Equations of State

Self-focusing of electromagnetic beams in collisional plasmas with nonlinear absorption

Ashutosh Sharma, M. P. Verma, and M. S. Sodha

Phys. Plasmas 11, 4275 (2004); http://dx.doi.org/10.1063/1.1776176 (5 pages) | Cited 15 times

Online Publication Date: 13 August 2004

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In this paper the formalism of self-focusing of electromagnetic waves is extended to include nonlinear absorption by the medium. A complex eikonal has been employed, which does not need any approximation about the relative magnitudes of the real and imaginary parts of the dielectric constant or their dependence on the irradiance of the beam. The specific case of collisional plasmas has been considered as an application of the theory. It is seen that the nonlinearity in absorption tends to cancel the effect of divergence on account of diffraction. The dependence of the beam width and attenuation on distance of propagation has been illustrated for specific cases. The relevance of the investigation to radio wave propagation has also been pointed out.
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52.38.Hb Self-focussing, channeling, and filamentation in plasmas
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.25.Mq Dielectric properties
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
back to top Magnetically Confined Plasmas, Heating, Confinement

Edge transport and the low-to-high transition in tokamaks with D-shaped magnetic flux surfaces

Robert G. Kleva, Parvez N. Guzdar, and W. Dorland

Phys. Plasmas 11, 4280 (2004); http://dx.doi.org/10.1063/1.1775010 (6 pages) | Cited 7 times

Online Publication Date: 16 August 2004

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Nonlinear, three-dimensional numerical simulations of finite-β drift-ballooning turbulence in the edge of tokamaks with D-shaped magnetic flux surfaces are presented. The simulations are based on the reduced Braginskii equations. The turbulent transport in tokamaks with D-shaped magnetic flux surfaces is directly compared to that in tokamaks with circular magnetic flux surfaces. The energy flux can be extremely different depending on the shape of the magnetic flux surfaces. While a tokamak with circular flux surfaces exhibits exceedingly poor confinement, an otherwise identical tokamak with D-shaped flux surfaces is in the high (H) mode where the transport rate is small. The magnitude of the energy flux in these two cases differs by a multiplicative factor larger than 1000.
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52.35.Ra Plasma turbulence
52.55.Fa Tokamaks, spherical tokamaks
52.25.Fi Transport properties
52.65.Kj Magnetohydrodynamic and fluid equation
back to top Inertially Confined Plasmas, Dense Plasmas, Equations of State

Inferring the capsule-absorbed radiation energy from experimental hohlraum radiation temperature

Tieqiang Chang, Guangyu Wang, Yunsheng Li, Jiatian Sheng, and Wenbing Pei

Phys. Plasmas 11, 4286 (2004); http://dx.doi.org/10.1063/1.1776564 (4 pages) | Cited 2 times

Online Publication Date: 16 August 2004

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For indirect laser fusion, the implosion is driven by the fusion capsule-absorbed radiation energy emitted by laser-produced plasma. However, the absorbed energy could hardly be directly measured experimentally and usually would require numerical simulation. This paper puts forward a method by which the capsule-absorbed radiation energy can be inferred from the measured time-dependent radiation temperature. In the method, the capusle-absorbed radiation energy is seen as an effective radiation energy loss and should be reflected in the experimental radiation temperature. Furthermore, it is not necessary to know what materials the capsule is made of or how it is constructed.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
back to top Ionospheric, Solar-system, and Astrophysical Plasmas

Macro-scale instability of the ion shell distribution function in the divergent solar wind

Valentin Shevchenko, Vitaly Galinsky, Roald Sagdeev, and Dan Winske

Phys. Plasmas 11, 4290 (2004); http://dx.doi.org/10.1063/1.1777589 (5 pages) | Cited 6 times

Online Publication Date: 16 August 2004

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As a result of cyclotron interaction with Alfvén waves propagating from the sun, pitch angle diffusion of resonant particles takes place and a shell-like distribution function of resonant ions is formed at each distance from the sun. Stability of the solar wind ion shell-like distribution function with respect to excitation of waves at larger distances is addressed. It is shown in linear approximation, that in the case when the phase velocity of Alfvén waves decreases with distance, ions with shell distribution excite outward propagating Alfvén waves with smaller phase velocities when they advance to larger distances. The nonlinear dynamics of the wave spectrum as well as the evolution of the ion distribution function are studied. The characteristic spectrum at the high-frequency edge of the magnetohydrodynamic fluctuations is explained.
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95.30.Qd Magnetohydrodynamics and plasmas
52.72.+v Laboratory studies of space- and astrophysical-plasma processes
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.25.Gj Fluctuation and chaos phenomena
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
52.25.Fi Transport properties
96.60.Vg Particle emission, solar wind
back to top Magnetically Confined Plasmas, Heating, Confinement

Structure of the edge density pedestal in tokamaks

Weston M. Stacey

Phys. Plasmas 11, 4295 (2004); http://dx.doi.org/10.1063/1.1777590 (10 pages) | Cited 11 times

Online Publication Date: 16 August 2004

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A “first-principles” model for the structure of the edge density pedestal in tokamaks between or in the absence of edge localized magnetohydrodynamic instabilities is derived from ion momentum and particle conservation and from the transport theory of recycling neutral atoms. A calculation for (high) H-mode tokamak discharge parameters indicates that the equations have a self-consistent solution which has an edge pedestal in the ion density profile and sharp negative spikes in the poloidal velocity and radial electric field profiles in the edge pedestal, features characteristic of H-mode edge profiles. These sharp negative spikes in radial electric field and poloidal rotation produce a peak in the inward ion pinch velocity in the sharp gradient (pedestal) region which produces an edge particle transport barrier. The calculated magnitude of the density at the top of the pedestal and the density gradient scale length and radial electric field in the pedestal region are comparable to measured values.
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52.55.Fa Tokamaks, spherical tokamaks
back to top Nonlinear Phenomena, Turbulence, Transport

Driven phase space holes and synchronized Bernstein, Greene, and Kruskal modes

L. Friedland, F. Peinetti, W. Bertsche, J. Fajans, and J. Wurtele

Phys. Plasmas 11, 4305 (2004); http://dx.doi.org/10.1063/1.1781166 (13 pages) | Cited 13 times

Online Publication Date: 16 August 2004

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The excitation of synchronized Bernstein, Greene, and Kruskal (BGK) modes in a pure electron plasma confined in Malmberg–Penning trap is studied. The modes are excited by controlling the frequency of an oscillating external potential. Initially, the drive resonates with, and phase-locks to, a group of axially bouncing electrons in the trap. These initially phase-locked electrons remain phase-locked (in “autoresonance”) during a subsequent downward chirp of the external potential’s oscillation frequency. Only a few new particles are added to the resonant group as the frequency, and, hence, the resonance, moves to lower velocities in phase space. Consequently, the downward chirp creates a charge density perturbation (a hole) in the electron phase space distribution. The hole oscillates in space, and its associated induced electric field constitutes a BGK mode synchronized with the drive. The size of the hole in phase space, and thus the amplitude of the mode, are largely controlled by only two external parameters: the driving frequency and amplitude. A simplified kinetic theory of this excitation process is developed. The dependence of the excited BGK mode amplitude on the driving frequency chirp rate and other plasma parameters is discussed and theoretical predictions are compared with recent experiments and computer simulations.
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52.35.Sb Solitons; BGK modes
52.27.Jt Nonneutral plasmas
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)
back to top Inertially Confined Plasmas, Dense Plasmas, Equations of State

A detailed simulation for the transmission spectrum of hot aluminium plasma

Fengtao Jin, Jiaolong Zeng, and Jianmin Yuan

Phys. Plasmas 11, 4318 (2004); http://dx.doi.org/10.1063/1.1775008 (5 pages) | Cited 10 times

Online Publication Date: 16 August 2004

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The experimental transmission spectrum [Jiamin Yang et al., Phys. Plasmas 10, 4881 (2003)] of hot aluminium plasma is simulated by using a detailed term accounting model. The fine absorption structures are reproduced reasonably well for both the absorption strength and the line positions. The discrepancies between the detailed simulation and the experiment show that the temperature gradient exists in the experimental sample. By fitting the measured transmission spectrum with the variation of the population of the ion stage, it is concluded that the experimental transmission spectrum was obtained mainly at the temperature of about 65 eV but overlapped by some lower temperature spectra of even down to 35 eV. The relative strength of the fine absorption lines within one stage of the ion cannot be reproduced accurately without considering the non-Boltzmann distributions among the energy levels of the ion.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.20.-j Elementary processes in plasmas
back to top Magnetically Confined Plasmas, Heating, Confinement

Toroidal rotation in DIII-D in electron cyclotron heating and Ohmic H-mode discharges

J. S. deGrassie, K. H. Burrell, L. R. Baylor, W. Houlberg, and J. Lohr

Phys. Plasmas 11, 4323 (2004); http://dx.doi.org/10.1063/1.1778751 (9 pages) | Cited 45 times

Online Publication Date: 18 August 2004

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Spatially and temporally resolved toroidal rotation measurements have been made in DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] discharges with no externally applied torque. The velocity measurements are made using the charge exchange recombination (CER) technique viewing emission from the intrinsic carbon impurity in deuterium discharges. Three cases have been studied: L mode and H mode with Ohmic heating and H mode with electron cyclotron heating (ECH). The ECH H mode has carbon counter-rotation in the center of the plasma, and co-rotation outside, where co- and counter- are relative to the direction of the toroidal plasma current. The Ohmic H mode has carbon rotation everywhere in the co-direction. Neoclassical theory is applied to compute the deuterium toroidal velocity and it is found that the counter-rotation measured for carbon in the core of the ECH H mode is also thus predicted for the bulk deuterium species. Short blips of neutral beams (NB) must be used for the CER technique and these blips do apply a toroidal torque. Care is taken to verify that a nonperturbative measurement is made; data from the first 2 ms of NB injection in each discharge are used for this measurement.
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52.55.Fa Tokamaks, spherical tokamaks
52.50.Gj Plasma heating by particle beams
52.50.Nr Plasma heating by DC fields; ohmic heating, arcs
52.50.Qt Plasma heating by radio-frequency fields; ICR, ICP, helicons
52.30.-q Plasma dynamics and flow
52.70.-m Plasma diagnostic techniques and instrumentation
52.25.Vy Impurities in plasmas
52.25.Fi Transport properties
52.80.-s Electric discharges
back to top Basic Plasma Phenomena, Waves, Instabilities

No additional flow continua in magnetohydrodynamics

J. P. Goedbloed, A. J. C. Beliën, B. van der Holst, and R. Keppens

Phys. Plasmas 11, 4332 (2004); http://dx.doi.org/10.1063/1.1774163 (9 pages) | Cited 8 times

Online Publication Date: 20 August 2004

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The classical continuous spectrum of fluid flow found by C.M. Case [Phys. Fluids 3, 143 (1960)] is contained in the Alfvén and slow continua of magnetohydrodynamics (MHD). Contrary to several statements in the literature, most recently by S.N. Bhattacharyya and A. Bhattacharjee [Phys. Plasmas 4, 3744 (1997)], there are no additional flow continua in MHD. Additional Eulerian continuum modes do exist in both fluids and plasmas, but they only involve non-Lagrangian perturbations of the density or the entropy, not of the pressure and the magnetic field.
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52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
95.30.Qd Magnetohydrodynamics and plasmas
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
47.65.-d Magnetohydrodynamics and electrohydrodynamics
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