[en] The derivation and application of macroscopic equations which describe the behavior of multicomponent relativistic plasmas are discussed. Within this context, the important points here considered can be summarized as follows: (1) Derivation of the fully relativistic fluid equations for a Maxwellian plasma and for a strongly magnetized plasma. In particular, the equations of state for thermal equilibrium distributions are derived. (2) Canonical formulation of the relativistic fluid equations in Eulerian and Lagrangian coordinates. Derivation of the Hamiltonian density and of the energy integral. (3) Application of the fluid equations to the study of the two-stream instability in homogeneous plasmas, with the inclusion of relativistic and thermal effects. It is shown that for sufficiently high beam energies (γ/sub b/ greater than √2) the effect of the thermal spread of the beam becomes destabilizing, provided it is small enough to allow the hydrodynamic approximation. (4) Investigation of the stability of a beam of finite cross-section. Emphasis is given to a class of incompressible surface modes which are not completely stabilized by the external magnetic field. This instability results from the interaction between anti-parallel currents. The growth rate is reduced if the beam has a diffuse boundary

[en] A variational principle is derived which describes the stationary state of the plasma column in a plasma centrifuge. Starting with the fluid equations in a rotating frame the theory is developed using the method of irreversible thermodynamics. This formulation easily leads to an expression for the density distribution of the l-species at sedimentation equilibrium, taking into account the effect of the electric and magnetic forces. Assuming stationary boundary conditions and rigid rotation nonequilibrium states the condition for thermodynamic stability integrated over the volume of the system reduces, under certain restrictions, to the principle of minimum entropy production in the stationary state. This principle yields a variational problem which is equivalent to the original problem posed by the stationary fluid equations. The variational method is useful in achieving approximate solutions that give the electric potential and current distributions in the rotating plasma column consistent with an assumed plasma density profile. (Author)

[en] A direct variational method based on an energy principle is applied to obtain approximate magnetohydrodynamic equilibria for tokamak plasmas. The geometry of the nested magnetic flux surfaces is specified by a model that includes displacement, elongation and triangularity effects. The radial dependence in flux coordinates is described by a set of consistent trial functions which allows analytical calculation of the flux-surface averaged internal energy density of the plasma. Approximate solutions of the variational problem are obtained for arbitrary aspect-ratio tokamaks using a one-parameter optimization procedure

[en] Current drive by electron Bernstein waves in the start-up phase of tokamak discharges is studied. A general analytical expression is derived for the figure of merit J/Pd associated with these waves. This is coupled with a ray tracing code, allowing the calculation of the total current generated per unit of incident power in realistic tokamak conditions. The resuts show that the electron Bernstein waves can drive substantial currents even at very low electron temperatures. (Author)

[en] The steady state behavior of the fully ionized, multiple species, rotating, magnetized plasma in a vacuum-arc plasma centrifuge is described in detail. The analysis is based on a multiple species fluid model which includes electromagnetic, pressure gradient, centrifugal and collisional forces, for each species, in cylindrical geometry. It is showm that there is a family of theoretically possible dynamical equilibrium configurations, which can be achieved by different combinations of ion rotation velocity, radial ion density distribution and radial dependence of internal electric potential. The parametric dependences of the various plasma parameters under equilibrium conditions, including the ion separation factor, are presented for a nickel-copper plasma. The numerical results are analysed and discussed on light of experimentally measured plasma characteristics in a vacuum-arc plasma centrifuge. (Author)

[en] In this work we describe the design and construction of a sector magnetic mass spectrometer. The main parts of the instrument are: ion source, grids (extraction, energy analysis and ion acceleration), electrostatic lens, magnetic sector and detector. All these components are kept inside a vacuum chamber evacuated by a turbomolecular pump. (author)

[en] The propagation characteristics of ion-acoustic negative solitons, in a multi-component plasma with negative ions, are investigated considering a Kinetic model which takes into account electron reflection and positive ion trapping in the negative potential well of the soliton. The Poisson equation is solved consistently using the Sagdeev potential formalism. It is verified that the kinetic effects associated with trapping of positive ions and reflection of electrons modify the results predicted by the simple Korteweg-de Vries fluid model in such a way that the Mach number is reduced as the ion temperature and the population of reflected electrons increase. (author)

[en] Small amplitudes steady-state ion-acoustic double layers are observed to form in a plasma transversed by a beam of cold electrons. The importance of turbulence in maintaining the double layer is demonstrated. The measured wave spectrum is in approximate agreement with models deriveted from renornalized turbulence theory. The general features of the double layer are compared with results from particle simulation studies. (author)

[en] A small amplitude steady-state double layer is observed to form in a plasma tranversed by cold drifting electrons, v_d < v_e. The double layers is shown to be associated with the anomalous resistivity caused by the ion-aeoustic instability driven by electron beam. The double layer is formed when the beam density is sufficienty large to exchange the instability by a bootstrap action, in agreement with particle simulation studies. (author)

[en] Some experiments done at the Plasma Physics Laboratory at INPE are described. In the first part, the double plasma machine used for the study of ion acoustic wave propagation is described, and the results obtained so far are shown. The second part consists in the description of a plasma centrifuge project. It contains some basic parameters of our apparatus used for isotope separation, through electromagnetic rotation of the plasma. (Author)