[en] The distribution and suspension of dust particles under the action of electrostatic, gravitational, ion-drag and neutral collision forces are investigated near the boundary of a dusty plasma. It is shown that the competition among the forces results in spatial oscillations (multi-layer) of the particle distribution. For sub-micron grains the ion-drag has a significant effect on the grain dynamics while for micrometer sized grains the gravity quickly dominates over other forces. The effect of the neutral gas flux is to enhance or diminish that of the gravity while the effect of the neutral viscosity is to shift the profile toward the wall. Under the force balance, the particles are suspended in a narrow region with sharp boundaries within the sheath. copyright 1997 American Institute of Physics

[en] The impurity radiation from a tokamak divertor can be significantly enhanced due to the formation of a V-shaped impurity radiation front and the effects of perpendicular plasma heat conduction. For some conditions, the transition to a V-shaped radiation front can have a bifurcation character, such that the impurity radiation region jumps from the divertor targets to the entrance into the divertor. The divertor geometry can play a significant role in the formation of a V-shaped impurity radiation front. The analysis of the energy transport and impurity radiation suggest that divertor geometries with open-quotes verticalclose quotes target, neutral gas recirculation where sidewalls, or their combination are the most attractive from the point of view of the formation of a V-shaped radiation front and the plasma energy loss. copyright 1998 American Institute of Physics

[en] At irradiation of the contaminated water reservoir with observed relatively high values of the weight of removed petroleum products, which indicates the presence of chemical sorption in addition to the physical adsorption on the surface of wood chips. This important effect will be take into account at radiation purification of water contaminated with various organic compounds, crude oil and phenol. Addition of small amount of water solution of the salts of potassium, sodium oxides or quaternary ammonium organic alkali associated with the acid group of silicic acid for a short period of time practically completely (96-100percent) coagulates the organic colloidal system, spilled petroleum products and modifies the components of the oil product, reducing their fluidity and evaporation. The spilled oil products localized in the form of huge viscous, amorphous bunches and frozen spots laying the surface of the land plot with relatively small dimensions and settle on the bottom of the reservoirs.

[en] The impact of two-dimensional (2-D) effects of energy transport on impurity radiation fronts in a tokamak divertor plasma is considered. It is shown that 2-D effects significantly alter both the physics of the fronts and the radiation loss from the divertor plasma, and may explain the experimental observations of impurity radiation region jumps from the target to the X point and easier access to a detached divertor regime in open-quotes verticalclose quotes target geometry in comparison with the open-quotes horizontalclose quotes case. copyright 1997 American Institute of Physics

[en] W. M. Stacey presents stability criteria for the thermal instability based on a linear one-dimensional (1D) slab model including the effects of ionization recombination [Phys. Plasmas 3, 2673 (1996)], large radial gradients and rotation [Phys. Plasmas 3, 3032 (1996)] and external edge heating [Phys. Plasmas 4, 134 (1997)]. The second paper is incorrectly presented as a two-dimensional (2D) analysis. The hypothesis for the poloidal asymmetry of the multifaceted asymmetric radiation from the edge (MARFE) is based on a misinterpretation of the linear results and contradicted by our own linear analyses in a 1D cylindrical [Phys. Plasmas 1, 2623 (1994)] and a 2D tokamak model [Plasma Phys. Controlled Fusion 39, 423 (1997)]. The explanation for the evolution into a detached plasma and for MARFE suppression by external edge heating are interesting hypotheses, supported by experimental observations. However, a 1D linear analysis does not offer the basis to support these hypotheses theoretically.copyright 1997 American Institute of Physics

[en] A toroidally viewing spectroscopic imaging system has been developed for the Tokamak de Varennes providing measurements of the poloidal distribution of the absolute radiated power of deuterium and impurity species in the upper divertor region. Real time digitization is achieved using a low cost PC based digital imaging system. This system is used to obtain measurements of the divertor strike point as well as the shape of the flux surfaces in the divertor. The diagnostic close-quote s excellent spatial resolution and toroidal view provides an opportunity to quantitatively compare the measured two dimensional (2D) radiated power distribution to that calculated from 2D Monte Carlo transport codes. These 2D images provide unique and valuable information on the physics of local plasma interactions with divertor components and particle transport in a closed divertor. Additionally, by using two cameras simultaneously, the line ratio technique can be applied to the images to estimate plasma parameters in the divertor. copyright 1997 American Institute of Physics

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[en] Short communication