New high-resolution spectroscopy system available in PSI-2 and measured W spectra analysed + modelled --> paper submitted
First B layers exposed to PSI-2 and measured spectra analysed; also B-H lines observed + O and other elements --> to be revisited!
Comparison exercise --> previously observed high erosion rates due to Ar2+ ions, sputtering by heavy impurities and problems in estimating ion flux on the target? --> now with new exposures (and altered parameters) more reasonable erosion estimates obtained --> ready to move to next phase! (and check the data with Ne)
Next steps: repeat the exercise with Ne, then proceed to other W samples
Report on the different regimes upon response to dust impacts: deformation, disintegration or dust becoming bound on the surface --> depends on the coating properties and velocity of dust particles --> also native oxide layers on (W) surfaces can change the behaviour - but no boundary effect for coatings
New samples produced in 2024: samples with half pristine, half coated surface + further studies performed
Next steps: impact of oblique incidence and target + dust temperature on delamination shape; effect of coating thickness on delamination?
Open question: response of B layers to dust impacts? But is this relevant in a reactor?!
Boronization layers analysed from (i) W-coated wall tiles and (ii) MPM samples --> thickness and homogeneity determined, O gettering capacity 0.5-0.9 O/B
10-60 nm of B after a campaign, 5-15 nm after an individual boronization --> thin layers; how about exposure to air --> that may be an issue
Next steps: sticking coefficient of B-H radicals? cavity samples --> challenging! comparable task on AUG!
Review of W films produced in 2024 - for LIBS campaigns and linear-machine experiments
New in 2024: nanocolumnar W films (crystalline rods) --> first attempts resulted in tilted rods while the Madrid teams had a different outcome --> largely dependent on critical parameters
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SP B.4 - production, characterization, and exposure of B reference samples
B layers produced and characterized (magnetron sputtering) --> B layers appear to detach from their W substrate (due to W oxide?) --> best to anneal W substrates before deposition and keep in vacuum (similar effect on steel but only after several months --> humidity effect)
B erosion in PSI-2 --> erosion rates 0.26-0.43 nm/s (PSI-2 beam profile), quite consistent for long-term and short-term exposures (rate can increase up to 0.6 nm/s) - these obtained by spectroscopy!
Next steps: comparison to layers produced by other groups
Possible follow-up exercise: chemical erosion of B layers? Sabina can study this
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SP B.4 - production and characterization of B reference samples
W dust particles: clear impact of deposition rate, D retention etc. by addition of water vapor on the production of nanoparticles; particles also become more "disconnected"
B dust particles: produced using both magnetron sputtering (nanoparticles) and plasma arcing (big clusters) --> inclusion of H, N, and O changes the properties of dust particles + some notable differences compared to W dust
Next step: comparing lab dust to dust coming from fusion devices + finishing the database