A. Wiltner

Deuterium inventory in the full-tungsten divertor of ASDEX Upgrade

The deuterium inventory in tungsten-coated divertor tiles used during the first full-tungsten plasma-facing wall phase of ASDEX Upgrade was measured by various methods of analysis. The D inventory in the inner divertor was still dominated by codeposition with residual carbon, whereas it was dominated by trapping in the thicker vacuum plasma sprayed tungsten layers at the outer divertor. The total inventory in the divertor area decreased by a factor of 5–10 compared with the period of carbon-dominated plasma-facing wall.

Tungsten erosion and redeposition in the all-tungsten divertor of ASDEX Upgrade

Net erosion and deposition of tungsten (W) in the ASDEX Upgrade divertor were determined after the 2007 campaign by using thin W marker stripes. ASDEX Upgrade had full-W plasma-facing components during this campaign. The inner divertor and the roof baffle were net W deposition areas with a maximum deposition of about 1×1018 W-atoms cm−2 in the private flux region below the inner strike point. Net erosion of W was observed in the whole outer divertor, with the largest erosion close to the outer strike point. Only a small fraction of the W eroded in the main chamber and in the outer divertor was found in redeposits in the inner divertor, while a large fraction was either redeposited at unidentified places in the main chamber or has formed dust.

Deuterium bombardment of carbon and carbon layers on titanium

Abstract Interaction of deuterium ions with highly oriented pyrolytic graphite and thin carbon layers on titanium are studied by X-ray photoelectron spectroscopy (XPS) measurements. The effects induced by the deuterium beam are compared to bombardment with chemically inert argon ions. XPS allows the identification of several carbon states: graphitic carbon, disordered graphitic carbon, ion-induced radiation defects in carbon, and carbidic carbon in the carbon films on titanium. Erosion of the carbon film by deuterium proceeds through two paths: first a chemical erosion with a cross-section of 4.7×10−17 cm2 removes elementary carbon. At the same time, carbidic carbon is eroded with a linear yield of 0.003 within the fluence range between 8×1016 and 1.4×1017 cm−2.

Chemical erosion of atomically dispersed doped hydrocarbon layers by deuterium

Abstract The chemical erosion of atomically dispersed Ti-doped (∼10 at.%) amorphous hydrocarbon layers (a-C:H:Ti) was investigated in the temperature range of 300–800 K for 30 eV deuterium impact. Compared to pyrolytic graphite, the methane production yield is strongly reduced at elevated temperatures. This reduction starts from temperatures just above room temperature and is even larger than for B-doped graphite. The reduction of the activation energy for hydrogen release may be the dominant interpretation for the decreased hydrocarbon formation. The ratio of emitted CD 3 to CD 4 increases with temperature for pyrolytic graphite and even stronger for the doped layers. The fluence dependence of the chemical erosion yield was determined, which is explained by enrichment of the dopant due to the preferential erosion of C.

Deuterium permeation through carbon-coated tungsten during ion bombardment

Deuterium permeation during ion bombardment through tungsten membranes coated by amorphous carbon films was investigated and compared with the permeation through bare tungsten. The membrane was bombarded by D3+ ions with energies of 200 and 1200 eV/D at a temperature of 873 K. The thickness of the amorphous carbon film was 120–170 nm. Detailed characterization of the carbon films were performed using AFM, NRA, RBS, FIB/SEM and XPS. The influence of the carbon films on permeation were strong for both ion energies, but different for each energy. In the case of 200 eV/D ions, the film was completely removed by the end of permeation due to intensive chemical sputtering, the lag time of permeation was much longer than for the bare membrane, and the permeation rate rose to a maximum value close to the bare membrane and then decreased to lower values. In the case of 1200 eV/D, the films were sputtered only very slowly, the lag time was much longer than in the case of the bare membrane but shorter than at 200 eV/...

Silver Metallization with Reactively Sputtered TiN Diffusion Barrier Films

The physical and electrical properties as well as thermal stability of reactively sputtered titanium nitride (TiN) film serving as a diffusion barrier was studied for silver (Ag) metallization. The thermal stability of Ag/TiN metallizations on Si with 12-nm-thick TiN barriers, as-deposited and after annealing at 300-650°C in N 2 /H 2 for 30 min, was investigated with sheet resistance measurement, X-ray diffraction, focused ion beam-scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. According to electrical measurement no change of sheet resistance was found after annealing at 600°C, but an abrupt rise appeared at 650°C annealing. There are two causes by which the Ag/TiN/Si structure became degraded. One is agglomeration of the silver layer, and the other is oxidation and diffusion which are also associated problems during thermal annealing.