Consistent treatment of critical plasma flows in high pressuredischarge ablative capillaries

A self-consistent solution of generalized, quasi-one-dimensional nonideal fluid equations describing the steady-state critical plasma flows in high pressure capillary discharges is presented. All three equations used (continuity, momentum and energy) include (ablative effects). No limitation to the case of ideal equation of state or to the spatial uniformity of the ionization degree is imposed. A numerical algorithm enabling the determination of self-consistent boundary conditions required for the integration of the differential equations is used. Illustrative result for typical physical parameters, namely, electrical current and radius and length of the capillary, are presented for polyethylene capillaries. The effects of changes in the geometrical characteristics of the capillary as well as in the electrical and radiative characteristics of the discharge on the plasma parameters are also considered     

Resistive vs. total power depositions by Alfvén modes in pre-heated low aspect ratio tokamaks

The power deposition of fast waves launched by a LFS located antenna in a pre-heated strongly non-uniform low aspect ratio tokamak (START) is investigated. The rigorous computational results indicate a total power deposition by far larger than that predicted for Alfvén continuum eigenmodes in cylindrical plasmas. For toroidal wave numbers |N|>1, the resistive and total power depositions are almost equal.     

A variational derivation of the velocity distribution functions for nonequilibrium,multispecies, weakly interacting,spherically symmetric many-body systems

The most probable velocity distribution function of each component,f _a , of a nonequilibrium multispecies spherically symmetric system of particles (stellar plasma atmospheres and winds, stellar systems, pellet-fusion systems) is analytically derived forthe case in which each component is described by the first six moments of f _a . This is achieved by the aid of a variational approach based on the requirement that the BoltzmannH function for the system be a minimum, subject to the constraints provided by the sets of six macroscopic parameters describing the nonequilibrium state. The use of the so-obtained velocity distribution functions for the closure of the moment equations as well as for the calculation of their collisional terms (via the Fokker-Planck equation) is discussed. The limitations on the maximum deviations from the equilibrium state which are consistent with the assumptions used are also indicated.     

The combined toroidicity,ellipticity and triangularity effects on the energy deposition of Alfvén modes in pre-heated,low aspect ratio tokamaks

The combined plasma non-uniformity effects on the energy deposition of Alfvén waves launched by an external antenna in pre-heated spherical tokamaks are investigated. The following relevant physical processes are here possible: (a) the emergence of gaps in the shear Alfvén continuum spectrum and the generation of discrete global Alfvén eigenmodes with frequencies inside the gaps; (b) multi-wave interactions, interactions of gaps of the same kind (e.g., toroidicity induced) and of different kinds (toroidicity, ellipticity and triangularity induced) as well as of secondary order gaps arising when a pair of modes is coupled to one or more modes through other coupling parameters; (c) basic wave-plasma interactions as propagation, reflection, mode-conversion, tunneling and deposition. Thus, we solved numerically the full 2D wave equations for the vector and scalar potentials, using a quite general two-fluid resistive tensor-operator, without any geometrical limitations. The results obtained indicate the existence of antenna-launched wave characteristics for which the power is most efficiently coupled in outer regions of plasmas, which is of special interest for low aspect ratio tokamaks, e.g., for the generation of non-inductive current drive as well as for turbulence suppression and transport barriers formation.