The major increase in discharge duration and plasma energy in a next step DT fusion reactor will give rise to important plasma-material effects that will critically influence its operation, safety and performance. Erosion will increase to a scale of several centimetres from being barely measurable at a micron scale in today's tokamaks. Tritium co-deposited with carbon will strongly affect the operation of machines with carbon plasma facing components. Controlling plasma-wall interactions is critical to achieving high performance in present day tokamaks, and this is likely to continue to be the case in the approach to practical fusion reactors. Recognition of the important consequences of these phenomena stimulated an internationally co-ordinated effort in the field of plasma-surface interactions supporting the Engineering Design Activities of the International Thermonuclear Experimental Reactor project (ITER), and significant progress has been made in better understanding these issues. The paper reviews the underlying physical processes and the existing experimental database of plasma-material interactions both in tokamaks and laboratory simulation facilities for conditions of direct relevance to next step fusion reactors. Two main topical groups of interaction are considered: (i) erosion/redeposition from plasma sputtering and disruptions, including dust and flake generation and (ii) tritium retention and removal. The use of modelling tools to interpret the experimental results and make projections for conditions expected in future devices is explained. Outstanding technical issues and specific recommendations on potential R&D avenues for their resolution are presented.

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Plasma{material interactions in current tokamaks and their implications for next step fusion reactors

An electronic device including a frame configured to be worn on the head of a user is disclosed. The frame can include a bridge configured to be supported on the nose of the user and a brow portion coupled to and extending away from the bridge and configured to be positioned over a side of a brow of the user. The frame can further include an arm coupled to the brow portion and extending to a free end. The first arm can be positionable over a temple of the user with the free end disposed near an ear of the user. The device can also include a transparent display affixed to the frame adjacent the brow portion and an input affixed to the frame and configured for receiving from the user an input associated with a function. Information related to the function can be presentable on the display.

Wearable device with input and output structures

Intermetallic-matrix composites—a review

The need for high performance materials in aerospace, automotive and industrial components operating at temperatures in the range of 1100–1500°C has led to a surge in the research and development of the refractory metal silicide based intermetallics, multiphase alloys and composites. The silicides of Mo, W, Ti, Nb and Cr are attractive for high melting points, strength retention and ductile behaviour, combined with reasonable to excellent oxidation resistance at elevated temperatures. The major limitation to the widespread use of structural silicides is their inherent brittleness and poor fracture toughness at room temperature, which may be improved further by suitable alloying or tailoring composite microstructures or use of innovative processing routes. The high temperature deformation behaviour of the structural silicides is complex, and depends on the composition and alloy content, crystal structure, character of bonding and orientation, microstructural constitution (nature of phases present ...

Mechanical behaviour and oxidation resistance of structural silicides

The invention provides an image display device that has an especially satisfactory display quality for animated images, and sufficiently suppresses the irregularities of display quality among pixels. The image display device includes a light emitting drive means that drives a light emitting means, based on an analog display signal inputted to the pixels, and a light emitting control switch for controlling a light-on or light-off of the light emitting means on one end of the light emitting drive means in each pixel.

Image Display Device

In electrically stimulating neural tissue it is important to prevent over stimulation and unbalanced stimulation which would cause damage to the neural tissue, the electrode, or both. It is critical that neural tissue in not subjected to any direct current or alternating current above a safe threshold. Further, it is important to identify defective electrodes as continued use may result in neural and further electrode damage. The present invention presents system and stimulator control mechanisms to prevent damage to neural tissue.

Method and apparatus to provide safety checks for neural stimulation

An inflatable mask with two ocular cavities can seal against a user's face by forming an air-tight seal around the periphery of the user's eye socket. The sealed air-tight ocular cavity can be pressurized to take ocular measurements. The mask can conform to the contours of a user's face by inflating or deflating the mask. In addition, the distance between the user and a medical device (e.g. an optical coherence tomography instrument) can be adjusted by inflating or deflating the mask. Also disclosed herein is an electronic encounter portal and an automated eye examination. Other embodiments are also described.

Inflatable medical interfaces and other medical devices, systems, and methods

Visor for a visual prosthetic apparatus

The thrust to develop new high temperature materials for advanced aircraft turbine engines has focused on composite systems based on metal-matrix, ceramic-matrix, intermetallic matrix and carbon-carbon composites. For the case of intermetallic matrix composites, candidate materials such as aluminides and silicides have been identified as potential materials due to their excellent oxidation resistance at high temperatures. More specific to the class of silicides, is molybdenum disilicide (NoSi{sub 2}), which has been used as a high melting intermetallic (2030 {degrees} C) for more than eighty years. One of the properties which has discouraged the application of MoSi{sub 2}, as well as other intermetallic compounds, is the inherent lack of ductility at low to intermediate temperatures. Plasma spraying as a means of fabricating composite structures of metals has been addressed recently by a number of researchers. In this paper the use of low pressure plasma deposition (LPPD) for producing spray deposits of MoSi{sub 2} and MoSi{sub 2} with a 20 volume fraction of tantalum is investigated. Initial results focusing on the as-deposited densities and fracture toughness of the spray deposited material are compared to those properties measured on conventionally hot pressed MoSi{sub 2}. Effects of post consolidation on fracture toughness of themore » spray deposits are also addressed.« less

Toughness of dense MoSi2 and composites produced by low pressure plasma deposition

Hot-pressed and plasma-sprayed specimens of MoSi2 have been examined by transmission electron microscopy both in the undeformed condition and when they were deformed by bending or hot hardness indentation. Hot-pressed specimens are found to contain 〈100〉 dislocations after deformation at lower temperatures (about 600°C or lower) and 1 2 〈111〉 dislocations after deformation at higher temperatures. High energy 1 2 〈331〉 dislocations previously reported in the literature are not observed but this may be due to their intrinsic instability. Twins are commonly observed, especially in undeformed plasma-sprayed MoSi2. Analysis of diffraction patterns shows that the twin plane is {112} and the twinning direction is 〈111〉; the twin boundary is {111} corresponding to a rotationh twin. The twins are suggested to be variants resulting from the hexagonal-to-tetragonal transformation at high temperatures. Silica particles are frequently seen in hot-pressed material on the grain boundaries and at triple points. However, no grain boundary phase is observed, even by high resolution electron microscopy, suggesting that silica does not wet the grain boundaries. Silica is less common in plasma-sprayed MoSi2 but there is a high density of Mo5Si3 particles due to silicon loss during processing.

Richard G. Castro

Papers

Method and apparatus to provide safety checks for neural stimulation

Inflatable medical interfaces and other medical devices, systems, and methods

Visor for a visual prosthetic apparatus

Toughness of dense MoSi2 and composites produced by low pressure plasma deposition

Dislocations, twins, grain boundaries and precipitates in MoSi2