No abstract available

[en] Fundamental processes of dust particles in low-temperature laboratory plasmas are summarized, particularly focusing on charging dynamics, in which the importance of electron energy distribution function is stressed. A delayed charging from local equilibrium charge may provide the energy to dust particles due to electrostatic field in the sheath, which may be the origin of spontaneously excited vertical oscillation. The dispersion relation for vertically polarized dust lattice wave is formulated, taking such a charging dynamics into account. Such dust waves excited externally as well as spontaneously are demonstrated experimentally. Recent observations show a great amount of dust near the divertor region in magnetic fusion devices. Role of dust in fusion devices are discussed in terms of tritium retention and safety. Some mechanisms for dust formation in fusion environment are suggested. (author)

[en] Neutral impurities ejected from Tokamak wall and limiter surfaces may travel several cm before being ionized very quickly upon entering the plasma edge. The influence of the unipolar sheath potential is exerted only within a very short distance of the surface and has no effect on neutral impurity atoms within a very short distance of the surface and has no effect on neutral impurity atoms which are subsequently ionized by charge-exchange collisions or electron impact ionization. However, secondary ions emanating from the limiter surfaces with kinetic energies less than the sheath potential will have essentially zero probability of traveling more than a few Debye lengths before being redeposited. Similarly, secondary ions originating at the first wall are redeposited as a result of the deflection produced by the magnetic field. Impurity influx resulting from sputtering would therefore be substantially reduced for surfaces which produce a very high ion/neutral ratio when sputtered. It has been previously shown that the high secondary ion yield associated with the alkali metal potassium does not apply to the bulk metal but pertains to ionic compounds and thin (mono-layer) films. Two processes are discussed as a means of producing these films in a self-sustaining manner compatible with the fusion reactor environment. (orig.)

[en] Ceramic materials used in the first wall and blanket regions of fusion reactors can provide very low radioactivity and high temperature systems with abundant raw material resources. Design problems arise in accommodating tensile stresses in structural members, however, with suitable designs, crack initiation, crack propagation and failures can be minimized. Several design concepts are discussed for inertial and magnetic confinement fusion reactors. A companion paper describes the analytical methods and results. (orig.)

[en] This report is an initial effort to identify issues affecting reliability and availability of solid and liquid wall designs for magnetic fusion power plant designs. A qualitative approach has been used to identify the possible failure modes of major system components and their effects on the systems. A general set of design attributes known to affect the service reliability has been examined for the overview solid and liquid wall designs, and some specific features of good first wall design have been discussed and applied to these designs as well. The two generalized designs compare well in regard to these design attributes. The strengths and weaknesses of each design approach are seen in the comparison of specific features

[en] It is known that NBI ion losses may pose a problem to the Wendelstein 7-X first wall, but the so-far utilized wall models had insufficient details for reproducing the locations and magnitude of the hot-spots. This study aims to exhaustively analyse the detailed wall loads in the reference magnetic configurations and in various plasma scenarios. The goal is to pinpoint the endangered plasma facing components and to calculate heat loads to them in preparation for the first NBI operations. This study can be used to prepare monitoring of the heat loads and paves the way to future searches of improved configurations. (paper)

[en] The results indicate that vaporized wall material moves rapidly into the plasma and interaction of the plasma with this vapor produces intense thermal radiation from the vapor. The consequence is a burst of energy deposition on the wall and rapid plasma thermal quench. The significance of these results is the indication of a process that intensifies the rate of energy deposition from a plasma disruption and consequently the extent of wall erosion. Because of assumptions required in the model, the predictions should be considered as approximate. The numerical results are sensitive to the rate of vapor expansion into the plasma and the rate of thermal radiation from the vapor. In future work, models for these processes will be refined. (orig.)

[en] As part of the First Wall/Blanket/Shield Engineering Test Program, a test bed called FELIX (Fusion ELectromagnetic Induction eXperiment) is now under construction at ANL. Its purpose will be to test, evaluate, and develop computer codes for the prediction of electromagnetically induced phenomenon in a magnetic environment modeling that of a fusion reaction. Crucial to this process is the sensing and recording of the various induced effects. Sensor evaluation for FELIX has reached the point where most sensor types have been evaluated and preliminary decisions are being made as to type and quantity for the initial FELIX experiments. These early experiments, the first, flat plate experiment in particular, will be aimed at testing the sensors as well as the pertinent theories involved. The reason for these evaluations, decisions, and proof tests is the harsh electrical and magnetic environment that FELIX presents

No abstract available

No abstract available