max-planck-institut für plasmaphysik euratom assoziation k. schmid sweg 12.09.2007 deuterium...
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Max-Planck-Institutfür PlasmaphysikEURATOM 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
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
+ ~4x1018 cm-2 s-1, Te~ 7eV, ne~ 4x1012 cm-3
CFC-Target
Axial spectroscopic field of view
Berylliumimpurityseeding
IRoptic
K. Schmid, MF-Seminar 23.01.2007
Results: Overview
•Target temperature during exposure ~ 1073K Factor of 10 to 20 between TDS & NRA
K. Schmid, MF-Seminar 23.01.2007
Results: Surface morphology of exposed samples
Very different surface morphology with Be seeding
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
K. Schmid, MF-Seminar 23.01.2007
Results: D-depth profiles
0.0 2.0x104 4.0x104 6.0x104 8.0x104 1.0x10510-5
10-4
10-3
10-20 2 4 6 8 10
D-c
on
cen
tra
tion
Depth (1015 cm-2)
CFC3 CFC3 (Degassed) CFC4 CFC5 (Be)
Depth (m)
Using NRA energy scans D depth profiles up to 8m 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 23.01.2007
Results: D-retention at different depths
•Most D is retained in Bulk (not entirely accessible by NRA)
K. Schmid, MF-Seminar 23.01.2007
Conclusions
D retention in CFC appears to saturate at levels of 1021 D/m2 fluences of 1026 to 1027 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.