No abstract available

No abstract available

[en] It is shown how a formally exact Kubo-like response theory equivalent to the Boltzmann equation theory of charged particle transport can be constructed. The response theory gives the general wavevector and time-dependent velocity distribution at any time in terms of an initial distribution function, to which is added the response induced by a generalized perturbation over the intervening time. The usual Kubo linear response result for the distribution function is recovered by choosing the initial velocity distribution to be Maxwellian. For completeness the response theory introduces an exponential convergence function into the response time integral. This is equivalent to using a modified Boltzmann equation but the general form of the transport theory is not changed. The modified transport theory can be used to advantage where possible convergence difficulties occur in numerical solutions of the Boltzmann equation. This paper gives a systematic development of the modified transport theory and shows how the response theory fits into the broader scheme of solving the Boltzmann equation. The discussion extends both the work of Kumar et al. (1980), where the distribution function is expanded out in terms of tensor functions, and the propagator description where the non-hydrodynamic time development of the distribution function is related to the wavevector dependent Green function of the Boltzmann equation

[en] More refined numerical calculations of trapped-ion anomalous transport in a 2-D slab, trapped-fluid model suggest an anomalous diffusion coefficient D approx. 3.5 x 10^-2 delta₀ a² νsub(i)sup(e)sup(f)sup(f) for a tokamak plasma without shear. This supersedes earlier results. The new formula is independently confirmed by two different analytical calculations. One of them uses a similarity analysis of unabridged Kadomtsev-Pogutse-type trapped-fluid equations and the multiperiodic spatial structure of the saturated trapped-ion wave found in both the earlier and the recent numerical calculations. The other calculation yields a class of exact nonlinear solutions of the trapped-fluid equations. The new shearless result is used to derive the anomalous diffusion with shear effect by a method described in an earlier paper. The new transport formulas have been numerically evaluated for several tokamaks in an IPP report, where the results are shown in graph form. (orig.)

[en] We examine the transport behaviour of non-interacting particles in a simple channel billiard, at equilibrium and in the presence of an external field. We observe a range of sub-diffusive, diffusive and super-diffusive transport behaviours. We find nonequilibrium transport that is inconsistent with the equilibrium behaviour, indicating that a linear regime does not exist for this system. However, we define a 'weak' linear regime that may lead to consistency between the equilibrium and nonequilibrium results. Despite the non-chaotic nature of the dynamics, we observe greater unpredictability (complexity) in the transport properties than is observed for chaotic systems. This observation seems at odds with existing complexity measures, motivating some new measures that attribute importance to the collective behaviour, rather than to the behaviour of individual system components. Such measures provide a new key for characterizing complexity in real-world phenomena

[en] Transport properties of granular systems are governed by Coulomb blockade effects caused by the discreteness of the electron charge. We show that, in the limit of vanishing mean level spacing on the grains, the low-temperature behavior of 1d and 2d arrays is insulating at any inter-grain coupling (characterized by a dimensionless conductance g). In 2d and g >> 1, there is a sharp Berezinskii-Kosterlitz-Thouless crossover to the conducting phase at a certain temperature, T _BKT. These results are obtained by applying an instanton analysis to map the conventional 'phase' description of granular arrays onto the dual 'charge' representation

[en] Radial transport produced by static nonaxisymmetric fields is thought to limit the confinement of non-neutral plasmas and experiments with applied asymmetries have verified that such fields do produce transport. A theoretical model of such transport is presented which is appropriate for long, thin plasmas. The theory allows for asymmetries with nonzero frequency and includes the linear collective response to applied wall voltages. For the regime where the effective collision frequency is large, the asymmetry-induced radial particle flux is derived from the drift kinetic/Poisson equations including collisions. For low collision frequencies a heuristic derivation is given. In both regimes the resulting transport is dominated by particles that move in resonance with the asymmetry. Possible applications of the theory to several experiments are discussed. copyright 1999 American Institute of Physics

No abstract available

[en] A local potato-plateau transport theory is presented. It is a nonradial averaged version of the original theory [Phys. Plasmas 4, 4331 (1997); 5, 953 (1998)]. The theory unifies conventional plateau theory and the potato-plateau theory. It is applicable at any radius. It is found that the ion heat conductivity is the same as that in the conventional theory in the region close to the magnetic axis

[en] This conference report summarizes the contributions to the EU-US workshop on Transport in Fusion Plasmas, Transport Barrier Physics held in Varenna, Italy, 4-7 September 2000. The workshop, whose main focus was on transport barriers, was organized into four sections: transport barrier physics, MHD effects concerning barriers, turbulence and core transport. This report is organized in a like manner. (author)