Abstract-Assembly of the superconducting stellarator Wendelstein 7-X is well advanced, and commissioning of the device is being prepared. A first draft of the commissioning tasks has been developed and will be discussed in this paper.

The effect of surface treatments, silane and alkali, on regenerated cellulose fibers was studied by using the treated fibers as reinforcement in lactic acid thermoset bioresin. The surface treatments were performed to improve the physico-chemical interactions at the fiber-matrix interface. Tensile, flexural and impact tests were used as indicator of the improvement of the interfacial strength. Furthermore, thermal conductivity, viscoelasticity measurements as well as microscopy images were made to characterize the fiber surface treatments and the effect on adhesion to the matrix. The results showed that silane treatment improved the mechanical properties of the composites as the silane molecule acts as link between the cellulose fiber and the resin (the fiber bonds with siloxane bridge while the resin bonds with organofunctional group of the bi-functional silane molecule) which gives molecular continuity in the interphase of the composite. Porosity volume decreased significantly on silane treatment due to improved interface and interlocking between fiber and matrix. Decrease in water absorption and increase in contact angle confirmed the change in the hydrophilicity of the composites. The storage modulus increased when the reinforcements were treated with silane whereas the damping intensity decreased for the same composites indicating a better adhesion between fiber and matrix on silane treatment. Thermogravimetric analysis indicated that the thermal stability of the reinforcement altered after treatments. The resin curing was followed using differential scanning calorimetry and the necessity for post-curing was recommended. Finite element analysis was used to predict the thermal behavior of the composites and a non-destructive resonance analysis was performed to ratify the modulus obtained from tensile testing. The changes were also seen on composites reinforced with alkali treated fiber. Microscopy images confirmed the good adhesion between the silane treated fibers and the resin at the interface.

For the first test operation of W7-X, only a limited set of seven diagnostics is considered to be mandatory. Among these are the Dispersion Interferometer for the electron density measurement and the ECE radiometer. Dispersion Interferometry using a 10.6 µm CO 2-laser and its second harmonic with no need for a reference line is widely independent of mechanical vibrations and drifts and thus developed as a candidate for steady state density control. The 32-channel ECE radiometer probing the electron temperature profile using Gaussian optics and a single broadband mixer is dedicated to track ECRH heating and perform first transport studies. Three reflectometers are being prepared to use the first plasmas for their test operation namely a Doppler reflectometer with an optimized Gauss telescope optics, a Doppler reflectometer with a fast steering antenna with no movable in-vessel parts capable for a fast scan of the turbulence Kspectrum, and a conventional correlation reflectometer probing the separatrix region.

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