Download - Max-Planck-Institut für Plasmaphysik EURATOM Assoziation K. Schmid SWEG 12.09.2007 Deuterium retention in graphite samples exposed to beryllium-seeded.

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


Results: Overview

•Target temperature during exposure ~ 1073K Factor of 10 to 20 between TDS & NRA


Results: Surface morphology of exposed samples

Very different surface morphology with Be seeding


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


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


Results: D-retention at different depths

•Most D is retained in Bulk (not entirely accessible by NRA)


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.