The stellarator Wendelstein 7-X (W7-X) is presently under construction at Greifswald, Germany, and the start of operation is planned in 2006. W7-X is a large `advanced stellarator' of the HELIAS type (R = 5.5 m, a = 0.55 m, B0 = 3 T, five periods, moderate shear and variable rotational transform 5/6 ⩽ ι ⩽ 5/4 at the boundary) with the aims of demonstrating the reactor potential of this stellarator line in steady state operation close to fusion relevant parameters. The capability of stationary operation requires the realization of a superconducting magnet system consisting of 50 modular coils and 20 planar coils, the operation of a 140 GHz ECR CW heat source of 10 MW, the installation of a divertor to handle the power and particle flux, and to limit the impurity fraction to tolerable levels. Additional heating schemes, ICRF and NBI, will be provided for flexible experimentation.

Two significant problems that need to be solved for any future fusion device are heat removal and particle control. A very promising method to attack these problems in tokamaks and helical devices is the use of a divertor, providing a controlled interaction zone between plasma and wall. By carefully designing a divertor, conditions can be created in front of the divertor targets, which lead to a sufficient reduction of the power load on the targets by strong radiation redistribution. Any solution of course needs to allow for an energy confinement which is at least sufficient for the realization of a fusion reactor. Since energy confinement has been found to be strongly related to edge anomalous transport and edge plasma profiles, the ultimate aim is to find an integral solution which is optimum with respect to exhaust, heat load and energy confinement.Two different types of divertors are presently being investigated in helical devices: the 'helical divertor' and the 'island divertor'. So far divertor concepts have been investigated only in a few helical devices. Theoretical and experimental efforts have mainly concentrated on the suitability of divertor magnetic field structures, while detailed studies of the divertor plasma properties for the two types of divertor configurations have only recently begun. In the course of this exploration, a promising new high-density H-mode (HDH) plasma operational regime has been discovered on the Wendelstein stellarator W7-AS. It benefits from high-energy (up to twice the value of the International Stellarator Scaling ISS95) and low impurity confinement times, complemented by edge radiated power fractions of up to 90% in detached regimes. This allowed quasisteady-state operation for up to 50 energy confinement times and so far was only constrained by machine operability.

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A favourable property of the stellarator concept is the potential of stationary operation within a magnetic configuration maintained by a superconducting coil system. For proof of principle the stellarator Wendelstein 7-X is presently under construction at Greifswald, Germany, and the start of operation is planned for 2007. The magnetic configuration of the confinement is a nonaxisymetric three-dimensional configuration with a helix-like magnetic axis and five identical magnetic field periods. As a first-step divertor design, an open divertor structure has been chosen, which benefits from the inherent divertor property of the magnetic configuration. The system will allow an effective particle and energy exhaust for a wide range of plasma and magnetic parameters. Experimental tools, e.g. localized heating, various heating schemas, gas feed and pellet injection, impurity doping and variation of the pumping speed together with appropriate diagnostics are provided. The purpose is to investigate different modes of operation for the divertor system and to evaluate an extended database for further improvement of the divertor.The main heating method will be 140 GHz ECR as a cw heat source of 10 MW. Additional heating schemes are ICRF and NBI.

ECR heating at Bo = 2.5T has been extensively used in the 1990 experimental period of the W VII-AS stellarator.As it is a low-shear experiment the magnetic configuration (especially details of the rotational transform profile) depends sensitively on plasma currents (pressure driven, ohmic, E C driven, Ohkawa current) which in turn have a strong influence on energy and particle confinement properties. For the stationary phase a transport analysis has been performed, yielding the profiles of the electron heat conduction and the ion particle diffusion coefficients. The former was subjected to a statistical analysis resulting in phenomenological expressions for xe and TE. First experiments using neutral beam injection (ECRH target plasma) as well as combined heating (NBI+ECRH) will also be discussed.

Substantial progress was made during the period 1981-1986 in plasma parameters, physics understanding, and improvement of the stellarator/heliotron concept. Recent advances include (1) substantial achievements in higher plasma parameters and currentless plasma operation, (2) new theoretical results with respect to higher beta limits, second stability region, effect of a helical axis, effect of electric fields on transport, and reduction of secondary currents; and (3) improvements to the reactor concept. The key issues have been further refined, and the short-term direction of the program is clear; a number of new facilities that were designed to resolve these issues are about to come into operation or are in the final design stages. This report summarizes these advances.

The article contains sections titled: 1. History 2. Properties 3. Occurrence 3.1. Abundance 3.2. Ores and Their Origin 3.3. Primary Deposits 3.4. Secondary Deposits 3.5. Recovery of Secondary Platinum Group Metals 3.6. Reserves and Resources 4. Mineral Dressing and Beneficiation 4.1. Treatment of Alluvial Platinum Deposits 4.2. Treatment of Primary Deposits 4.3. Treatment of Nickel Ores 4.4. Treatment of Metal Scrap 4.5. Treatment of Dross 4.6. Treatment of Supported Catalysts 4.7. Treatment of Solutions 5. Dissolution Methods 5.1. Dissolution in Aqua Regia 5.2. Dissolution in Hydrochloric Acid–Chlorine 5.3. Dissolution in Hydrochloric Acid–Bromine 5.4. Other Dissolution Processes 5.5. Dissolution by Salt Fusion 6. Separation of Platinum Group Metals 6.1. Chemistry of Platinum Group Metal Separation 6.2. Older Separation Processes 6.3. Current Separation Processes 6.4. Processes Used in Coarse Separation 6.5. Purification 6.6. Conversion of Salts into Metals 6.7. Partial Purification 6.8. Treatment of Internally Recycled Material 6.9. Construction Materials 7. Platinum Group Metal Compounds 7.1. Inorganic Compounds 7.1.1. Platinum Compounds 7.1.2. Palladium Compounds 7.1.3. Rhodium Compounds 7.1.4. Iridium Compounds 7.1.5. Ruthenium Compounds 7.1.6. Osmium Compounds 7.2. Organic Compounds 8. Alloys 8.1. Alloy Systems 8.2. Special Alloys 8.3. Methods of Treatment 9. Quality Specifications and Analysis 9.1. Quality Specifications 9.2. Qualitative Analysis 9.3. Quantitative Analysis 9.4. Purity Analysis 9.5. Trace Analysis 10. Uses 10.1. Jewelry, Coinage, Investment 10.2. Apparatus 10.3. Heterogeneous Catalysts 10.4. Fuel Cells 10.5. Homogeneous Catalysts 10.6. Automotive Emission Control Catalysts 10.7. Sensors 10.8. Electrical Technology 10.9. Electronics 10.10. Coatings 10.10.1. Coatings Produced by Electrolysis 10.10.2. Coatings Produced by Chemical Reaction 10.10.3. Coatings Produced by Physical Methods 10.11. Dental Materials 11. Economic Aspects 11.1. Supply 11.2. Demand 11.3. Prices 11.4. Commercial Aspects 12. Toxicology

The Wendelstein 7-X Stellarator (W7-X)is the next step device in the stellarator line of IPP Garching. A new branch of IPP is being built at Greifswald, Germany, to house W7-X. The design of W7-X is based on physics principles, which are discussed in the light of experimental results from the W7-AS stellarator. The experiment aims at demonstrating the inherent steady state capability of stellarators at reactor relevant plasma parameters and is therefore equipped with a modular superconducting twisted coil system. The 3D magnetic configuration of W7-X asks for a special divertor solution for steady state heat removal and decoupling of the vessel wall from the plasma. The status of the design and construction of W7-X including heating systems, divertor and diagnostics is presented.