Max-Planck-Institut für Plasmaphysik EURATOM Assoziation K. Schmid SWEG Deuterium retention in graphite samples exposed to beryllium-seeded plasma in PISCES-B K. Schmid, R. Pugno and the PISCES-B Team
K. Schmid, MF-Seminar 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
K. Schmid, MF-Seminar Results: Overview Target temperature during exposure ~ 1073K Factor of 10 to 20 between TDS & NRA
K. Schmid, MF-Seminar Results: Surface morphology of exposed samples Very different surface morphology with Be seeding
K. Schmid, MF-Seminar 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
K. Schmid, MF-Seminar 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
K. Schmid, MF-Seminar Results: D-retention at different depths Most D is retained in Bulk (not entirely accessible by NRA)
K. Schmid, MF-Seminar Conclusions D retention in CFC appears to saturate at levels of D/m 2 fluences of to 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.