The chemical erosion of carbon in interaction with a hydrogen plasma has been studied in detail in ion beam experiments, and erosion yield values are available as a function of ion energy and surface temperature. However, the conditions in the ITER divertor cannot be simulated by ion beam experiments, especially as far as ion flux is concerned.Therefore, a joint attempt was made through the EU Task Force on plasma-wall interaction and the international tokamak physics activity involving seven different fusion devices and plasma simulators to clarify the flux dependence. For each data point the local plasma conditions were normalized to an impact energy of 30 eV, care was taken to select data for a surface temperature close to the maximum yield or room temperature and the calibration of the diagnostic was performed in situ. Through this procedure the previous large scatter was significantly reduced, revealing a clear trend for a decreasing yield with increasing ion flux, . After the attribution of an error to each data point a fit using Bayesian probability analysis was performed, yielding a decrease in the erosion yield with −0.54 at high ion fluxes.

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Graphite and advanced carbon fiber composites (CFC) are widely used inside the vacuum vessel of magnetic fusion devices. However, erosion by chemical sputtering via hydrocarbon formation might limit their application as target material in future machines like ITER. The first systematic study of the chemical erosion of graphite and different CFCs (including a silicon-doped one) as a function of ion flux density in the range of 1.4 × 10 21 -5 × 10 22 m -2 s -1 was performed in the plasma generator PSI-1. The results of three different analysis methods agree within about 40%.No differences in the chemical erosion yields between hydrogen and deuterium exposures are found for the various materials. In contrast, the erosion yields differ up to a factor of two for the different CFC-materials. In general, the chemical sputtering yields decrease with increasing ion flux density according to -0.6 reaching levels below 1% at the highest fluxes. Scanning electron microscopy (SEM) and energy dispersive Xray analysis (EDX) show preferred erosion in the area between the carbon fibers.

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Several novel types of detectors for the measurement of electromagnetic radiation in the THz spectral range are described. Firstly, detectors based on pyroelectric foil coated with different absorbers have been developed focusing on the following features: high accuracy due to well-characterized absorption, high sensitivity, large area absorbers and frequency and polarization independence. A three-dimensional design with five absorptions gave an overall absorption of more than 98 %. Secondly, detectors based on pyroelectric foils with thin metal layers were realized. An absorption of 50 % can be obtained if the thickness of the layers is carefully adjusted. According to electromagnetic theory this degree of absorption is independent of the polarization and frequency of the radiation in a wide range from at least 20 GHz to 5 THz. The third type of detector is based on a new type of volume absorber with a polished front surface and a gold-coated back side. It is the absorber of choice of the standard power detector for disseminating the spectral power responsivity scale. This standard detector allows the application of a physical model to calculate its spectral responsivity in the range from 1 THz to 5 THz if the detector has been calibrated at one single frequency. Finally, a THz detector calibration facility was set up and is now in operation at PTB to calibrate detectors from customers with an uncertainty as low as 1.7 %.