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Preliminary results from XP604 Deposition Studies. Quartz crystal microbalances location: Bay H top & bottom, 7 cm ‘behind’ 7 cm wide gap in tiles & Bay I midplane 10 cm ‘behind’ limiter. Quartz Crystal. Thermocouple.
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Preliminary results from XP604 Deposition Studies Quartz crystal microbalances location: Bay H top & bottom, 7 cm ‘behind’ 7 cm wide gap in tiles & Bay I midplane 10 cm ‘behind’ limiter. Quartz Crystal Thermocouple • Quartz crystal oscillates at ~ 5.9 MHz, exact frequency depends on mass and on temperature. • Deposition inferred from change in frequency (measured to ~0.1 Å, ~0.1 Hz), density 1.6 g/cm3 assumed. • Temperature effect subtracted using thermocouple data (excl. transients). • Data accumulated continuously 24/7. NSTX Physics Meeting 20th March 2006
Issue: Are volatile hydrocarbons a major player in material migration in tokamaks ? (issue for T retention/removal in ITER) Conclusions so far: • Large step up in deposition on first shot of day is independent of 30 min GDC • Net deposition in shorter duration shots suggests contribution of startup / ramp down phase important. • Analysis on going, - will be presented at PSI-17 conference in May. Bay I midplane Bay H top Bay H bot. Shot times marked with ‘x’