The design and characterization of an innovative device for plasma cleaning, based upon a non-conventional radio-frequency discharge, is described. The RF fields are produced by an antenna placed inside the metallic vacuum chamber. Theoretical models are described to calculate both the electro-magnetic field structure and the spatial impurity distribution, due to erosion of the antenna. The electron energy distribution function is determined with a standard RF-filtered electrostatic probe; it is found that the plasma is well described by a Druyvesteyn energy distribution function.

An approach for the theory of nonlocal magnetorotational and convective instabilities in a rotating plasma is developed, on the basis of the surface wave concept, which allows the derivation of useful analytical results.It is assumed that the rotation frequency has a step-like profile, so that a narrow transition layer separates two regions with different rotation frequencies. The one-fluid magnetohydrodynamic (MHD) model for description of the perturbed plasma dynamics is used. It is shown that in the case of magnetized plasma the main properties of the nonlocal (surface-wave) instabilities are similar to those of the local ones.

In this work we analyze the transport processes in solar loops considering a collisional plasma and high longitudinal plasma flow. The general theory of the neoclassical transport in toroidal configurations with a noncircular cross-section is applied to explain the transport processes in some kinds of solar loops, modeling the solar loop as a toroidal plasma column. The plasma is assumed to be in the collisional regime and to have particle longitudinal flow along the solar loop axis. The poloidal velocity and the radial fluxes of the particles and the ion heat flux are derived in this article. It is shown that the particle poloidal velocity can be measured giving rise to the possibility of having additional connections between the plasma macroscopic parameters, which are very important for the solar loops diagnostic. It is also shown that the particle and heat fluxes are on the ''classical'' level, within the factor of an order of magnitude. We hope that such an approach (together with other theories) can help to explain the transport processes in solar loops, whose shapes are similar to toroidal configurations.

The design, construction, and characterization of an electron-cyclotron-resonance (ECR) plasma device and its utilization for growing AlN polycrystals are described in detail. The plasma density and electron temperature were measured by two types of Langmuir probes under different conditions of magnetic configuration and RF substrate polarization. For the investigated nitrogen plasmas, the electron temperature increases towards substrate holder and decreases with pressure. The magnetic configuration and plasma parameters required for successful growth of polycrystal aluminum nitride have been determined.

In this work, we discuss the preliminary analysis of some disruptive plasma discharges in the TCABR tokamak, operating in the high density limit. The Fourier analysis of the MHD activity was greatly facilitated because the magnetic coils inside the TCABR were installed as to take into consideration the toroidal geometry of the system, in a straight forward manner. What we have observed is that the m = 3, 4 and 7 MHD components dominate during almost the whole discharge duration, whereas the m = 2 MHD mode increased substantially just before the occurrence of a major disruption. Also, we could estimate the angular velocity of the magnetic islands, which was observed to increase up to three times just before the major disruption.

The results of experiments on Alfvén wave current drive and plasma heating in the TCABR tokamak are analyzed with the help of a numerical code for simulation of the diffusion of the toroidal electric field. It permits to find radial distributions of plasma current density and conductivity, which match the experimentally measured total plasma current and loop voltage changes, and thus to study the performance of the RF system during Alfvén wave plasma heating and current drive experiments. Regimes with efficient RF power input in TCABR have been analyzed and revealed the possibility of noninductive current generation with magnitudes up to ~8 kA. The increase of plasma energy content due to RF power input is consistent with the diamagnetic measurements.

A two dimensional code ALTOK, which is designed for calculating plasma heating due to radio frequency fields in the Alfvén and in Ion Cyclotron Ranges of Frequencies in axisymmetric tokamaks, is used to analyze Alfvén wave absorption in multi species plasmas in TCABR (Tokamak Chauffage Alfvén Brasilien) [Nucl.Fusion 30, 503 (1996)]. A good agreement between the results obtained with ALTOK code calculations and with a two dimensional kinetic code [Phys. Plas., 6 (1999) 2437] is shown for Alfvén wave dissipation in hydrogen plasmas. The global Alfvén wave resonance of the m = 0 mode is found to be the best candidate to explain some heating regimes in TCABR.

A new regime of runaway discharges has been observed in the TCABR tokamak. One of the most distinctive features of this regime is the effect of plasma detachment from the limiter. This experimental fact can only be explained by the volume recombination, which requires a low-temperature plasma. The analysis of the energy and particle balance in the system plasma-relativistic runaway beam in TCABR, which takes into account only the collisional mechanism of the heat transfer from runaways to thermal electrons, predicts electron temperatures Te = 0.1 - 2 eV; the temperature decreases with the neutral density increase. The recombination process with the rate constant around 10-16 m³/s is required for the explanation of plasma density behavior in the experiment. At present, it is difficult to conclude about the mechanism of recombination. More reliable and detailed experimental data, mainly about the plasma temperature, are necessary.

General metrics of large aspect ratio tokamaks is used in the paper. General expressions for the neoclassical poloidal plasma rotation <img src="http:/img/fbpe/bjp/v32n1/03eq01.gif"> and radial ion heat flux gammaTi are obtained. Their dependence on the squared Mach number alpha = <img src="http:/img/fbpe/bjp/v32n1/03eq02.gif" align="absMiddle"> is analyzed (here Uzetai is the ion toroidal velocity and c s is the sound velocity, respectively). Some interesting peculiarities of this dependence are emphasized.