Demonstrating improved confinement of energetic ions is one of the key goals of the Wendelstein 7-X (W7-X) stellarator. In the past campaigns, measuring confined fast ions has proven to be challenging. Future deuterium campaigns would open up the option of using fusion-produced neutrons to indirectly observe confined fast ions. There are two neutron populations: 2.45 MeV neutrons from thermonuclear and beam-target fusion, and 14.1 MeV neutrons from DT reactions between tritium fusion products and bulk deuterium. The 14.1 MeV neutron signal can be measured using a scintillating fiber neutron detector, whereas the overall neutron rate is monitored by common radiation safety detectors, for instance fission chambers. The fusion rates are dependent on the slowing-down distribution of the deuterium and tritium ions, which in turn depend on the magnetic configuration via fast ion orbits. In this work, we investigate the effect of magnetic configuration on neutron production rates in W7-X. The neutral beam injection, beam and triton slowing-down distributions, and the fusion reactivity are simulated with the ASCOT suite of codes. The results indicate that the magnetic configuration has only a small effect on the production of 2.45 MeV neutrons from DD fusion and, particularly, on the 14.1 MeV neutron production rates. Despite triton losses of up to 50 %, the amount of 14.1 MeV neutrons produced might be sufficient for a time-resolved detection using a scintillating fiber detector, although only in high-performance discharges.

WENDELSTEIN 7-X (W7-X) is a stellarator presently under construction and assembly in Greifswald, Germany. The superconducting magnet system of W7-X consists of planar and non planar coils. The electromagnetic forces on the superconducting magnet are supported by backing of all coils against a central ring and by wedging among coil casings through "Narrow Support Elements" (NSE) that have to satisfy very specific requirements. Anti friction MoS 2 coatings have been developed and tested at room and cryogenic temperature (77K) to allow relative sliding of adjacent coils under load without stickslip to avoid coil quenching. The influence of thickness on the coating endurance has been demonstrated. To prevent ageing both constructive methods and protective top coats have been investigated. This paper describes the atomic sputter deposition technique, the reduced and full-scale tribological tests, ageing tests and arrangements to protect the coatings from humidity and oxidation which have been carried on so far.

Abstract-The actively water-cooled In-Vessel Components (IVCs) of the stellarator Wendelstein 7-X consist of the divertor, the first wall protection components, the port liners, each designed for different loading conditions, and the associated pipework, the control coils, the cryo-pump system, the Glow discharge electrodes, and a set of diagnostics. The divertor, designed for high heat fluxes, is a set of 10 target and baffle units arranged along the plasma surface. The design and production of these high heat flux (HHF) components is a challenging task. The divertor target elements, which are based on flat CFC (carbon-carbon fibre composite) tiles bonded via active metal casting onto CuCrZr cooling structures required intensive development and testing to reach a reliable performance; removing, under stationary conditions, 10 MW/m 2 .Industrially manufactured high quality target elements have been delivered and assessed, and the process of incorporating them into assembly units, so-called modules, has begun. The time scale for the completion of the HHF divertor has been held for the last four years and the final delivery of the HHF divertor is still planned in 2017. In parallel to the realization of the divertor, most of the remaining IVCs have been defined, developed, designed and fabricated and the installation of many of these components has begun. Some of these components can also be expected, for a short period of time, to receive high heat loads approaching those of the divertor. These components will be described, in detail, from conception to realization.

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