Diffusion of As into Ge from a GaAs overlayer deposited on $p$ -type Ge substrates has been studied by means of secondary ion mass spectrometry. A concentration-dependent diffusion of As atoms was observed in addition to the concentration-independent diffusion of Ga and As atoms. The concentration dependence is explained by a Fermi-level-dependent diffusion model. Arsenic atoms are shown to diffuse through Ge vacancies with the charge states 2− and 0. No presence of the singly negatively charged vacancies was observed, indicating that Ge vacancy could be a negative $U$ center.

The paper reports the first demonstration of in situ laser-induced desorption — quadrupole mass spectrometry (LID-QMS) application on a large scale fusion device performed in summer 2023. LID-QMS allows direct measurements of the fuel inventory of plasma facing components without retrieving them from the fusion device. The diagnostic desorbs the retained gases by heating a 3 mm diameter spot on the wall using a 1 ms long laser pulse and detects them by QMS. Thus, it can measure the gas content at any wall position accessible to the laser. The successful LID-QMS application in laboratory scale and on medium size fusion devices has now been demonstrated on the larger scale and it is already foreseen as tritium monitor diagnostic in ITER. This in situ diagnostic gives direct access to retention physics on a short timescale instead of campaign-integrated measurements and can assess the space-resolvedefficacy of detritation methods. LID-QMS can be applied on many materials: on Be deposits like in JET, B deposits like in TEXTOR, C based materials or on bulk-W.

A selected set of samples from JET-ILW divertor tiles exposed in 2011–2012 has been analysed using thermal desorption spectrometry (TDS). The highest amount of deuterium was found on the regions with the thickest deposited layers, i.e. on the horizontal (apron) part and on the top part of Tile 1, which resides deep in the scrape-off layer. Outer divertor Tiles 6, 7 and 8 had nearly an order of magnitude less deuterium. The co-deposited layers on the JET tiles and the W coatings contain C, O and Ni impurities which may change the desorption properties. The D₂ signals in the TDS spectra were convoluted and the positions of the peaks were compared with the Be and C amounts but no correlations between them were found. The remaining fractions of D in the analysed samples at ITER baking temperature 350 °C are rather high implying that co-deposited films may be difficult to be de-tritiated.