Max-Planck-Institut f¼r Plasmaphysik EURATOM Assoziation K. Schmid SWEG 12.09.2007 Deuterium...
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Max-Planck-Institut fr Plasmaphysik EURATOM Assoziation K. Schmid SWEG 12.09.2007 Deuterium retention in graphite samples exposed to beryllium-seeded plasma in PISCES-B K. Schmid, R. Pugno and the PISCES-B Team Slide 2 K. Schmid, MF-Seminar 23.01.2007 Experimental setup 102 mm 153 mm 195 mm Cooled target holder Thermo- couple High temperature MBE effusion cell used to seed plasma with evaporated Be 12 PISCES-B Plasma D + ~4x10 18 cm -2 s -1, T e ~ 7eV, n e ~ 4x10 12 cm -3 CFC-Target Axial spectroscopic field of view Beryllium impurity seeding IR optic Slide 3 K. Schmid, MF-Seminar 23.01.2007 Results: Overview Target temperature during exposure ~ 1073K Factor of 10 to 20 between TDS & NRA Slide 4 K. Schmid, MF-Seminar 23.01.2007 Results: Surface morphology of exposed samples Very different surface morphology with Be seeding Slide 5 K. Schmid, MF-Seminar 23.01.2007 Results: D retention in CFC vs. Fluence Based on TDS the retention in CFC appears to saturate Still issues whether all D was detected in the TDS measurements Does not include the influence of co-deposition on retention Be seeding and the resulting Be/C mixed surface layer do not influence retention Slide 6 K. Schmid, MF-Seminar 23.01.2007 Results: D-depth profiles Using NRA energy scans D depth profiles up to 8 m have been measured CFC3 and CFC4 show identical depth profile despite factor of 10 in D fluence Supports saturation For Be seeded plasmas (CFC5 ) the bulk retention is slightly higher Pores closed by Be ? D amount in degassed sample close to detection limit Supports validity of TDS Slide 7 K. Schmid, MF-Seminar 23.01.2007 Results: D-retention at different depths Most D is retained in Bulk (not entirely accessible by NRA) Slide 8 K. Schmid, MF-Seminar 23.01.2007 Conclusions D retention in CFC appears to saturate at levels of 10 21 D/m 2 fluences of 10 26 to 10 27 for temperatures of 1073K The NRA measurements support the D retention data obtained by TDS. But: most D is retained deep in the bulk which is not accessible by NRA TDS may still have missed some D While the D retention saturates under these experimental conditions, the additional retention due to co-deposition may still lead to higher D retention for ITER.