1. SEWG Fuel Retention July 2008 © Matej Mayer Fuel retention in ASDEX Upgrade tungsten coatings M. Mayer, M. Balden, K. Krieger, S. Lindig, O. Ogorodnikova, V. Rohde, K. Sugiyama, and ASDEX Upgrade Team Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching, Germany Retention in ASDEX Upgrade from post-mortem studies First results on modelling of ASDEX Upgrade retention Surface modifications (blistering)

2. SEWG Fuel Retention July 2008 © Matej Mayer Retention in ASDEX Upgrade from post-mortem studies

3. SEWG Fuel Retention July 2008 © Matej Mayer W coverage in AUG 2002 – 2007 Step by step replacement of C tiles by W coated tiles 3 – 4 µm W-PVD on most tiles 200 µm plasma-sprayed W at outer strike point

4. SEWG Fuel Retention July 2008 © Matej Mayer Deuterium inventory C-dominated campaign 2002/2003 D on divertor tiles 0.9 – 1.3 g D below roof baffle 0.4 g in 3000 s Full W campaign 2007 D on divertor tiles 0.15 – 0.23 g D below roof baffle 0.03 g in 3000 s 6A 4 9B 1A 3A 4940 s 2620 s

5. SEWG Fuel Retention July 2008 © Matej Mayer Deuterium inventory in inner divertor of all-W machine Correlation between distributions of C and D D inventory in inner divertor still dominated by C-codeposition 6A 4

6. SEWG Fuel Retention July 2008 © Matej Mayer Deuterium inventory in outer divertor of all-W machine D inventory in outer divertor dominated by trapping in W Deep diffusion (> 3 µm) observed for VPS layers at outer strike point 3B 1

7. SEWG Fuel Retention July 2008 © Matej Mayer AUG divertor: Evolution of D inventory Carbon dominated machine Total D-inventory dominated by inner divertor and remote areas All-W machine Boronizations result in high D-inventory, co-deposition with B (2005/2006 campaign) D-inventory dominated by trapping in VPS-layers at outer strike point Decrease of total D-inventory by factor 5 – 10 from C-dominated to all-W

8. SEWG Fuel Retention July 2008 © Matej Mayer First results on modelling of ASDEX Upgrade retention

9. SEWG Fuel Retention July 2008 © Matej Mayer Retention as function of fluence VPS-W Laboratory and AUG data (VPS-W from tile 1) available Polycrystalline W Laboratory and AUG data (Langmuir probes) available 4 µm PVD-W No data (with known fluence/retention) available Assume same properties as polycrystalline W 4 µm thickness taken into account I 4µm = 0.67 x I Total

10. SEWG Fuel Retention July 2008 © Matej Mayer 1 3B 2 3A Incident fluence Outer divertor Ion fluence measured with Langmuir probes on tile 1 Extrapolation to tiles 2, 3A Fluence on 3B from erosion in 2004/2005 Inner divertor Assume identical number of ions as outer divertor 4.2 m 2, 10 22 ions/m 2 s Roof baffle Assume 3.3 m 2, 10 21 ions/m 2 s Main chamber Assume 8 m 2, 10 21 ions/m 2 s and 32 m 2, 10 19 ions/m 2 s Codeposition with C 1.9x10 19 C-atoms/s, D/C = 0.4

11. SEWG Fuel Retention July 2008 © Matej Mayer 1 3B 2 3A Modelling: Outer divertor Good agreement between model and experimental data, keeping the uncertainties in mind

12. SEWG Fuel Retention July 2008 © Matej Mayer Modelling: Full ASDEX Upgrade Good agreement for outer divertor Model gives too high inventory for inner divertor More realistic fluence data necessary

13. SEWG Fuel Retention July 2008 © Matej Mayer Modelling: Work in progress Ion fluences for inner divertor K. Krieger, July 2008 Temperature history of outer divertor for 2007 campaign A. Herrmann, July 2008 Inventory in 4 µm PVD-W as function of fluence O. Ogorodnikova, October 2008

14. SEWG Fuel Retention July 2008 © Matej Mayer Surface modifications (blistering)

15. SEWG Fuel Retention July 2008 © Matej Mayer = 10 26 D/m 2, T irr = 550 K = 10 26 D/m 2, T irr = 583 K Lab studies, 38 eV D-ions: BlistersAUG, Langmuir-probes: Blisters V. Kh. Alimov

16. SEWG Fuel Retention July 2008 © Matej Mayer Lab studies, 38 eV D-ions: BlistersAUG, Langmuir-probes: Blisters Blisters are not hollow! V. Kh. Alimov

17. SEWG Fuel Retention July 2008 © Matej Mayer Lab studies, 38 eV D-ions: BlistersAUG, Langmuir-probes: Blisters Often (always?) widened cracks (grain boundaries?) below blisters V. Kh. Alimov

18. SEWG Fuel Retention July 2008 © Matej Mayer T irr = 515 K T irr = 567 K Lab studies, 38 eV D-ions: SpongeAUG, Langmuir-probes: Sponge Sponge-like structures are observed V. Kh. Alimov

19. SEWG Fuel Retention July 2008 © Matej Mayer Summary Retention in ASDEX Upgrade: Decrease of trapped D in divertor by factor 5 – 10 from C-dominated to all-W machine D-inventory in all-W machine determined by deep diffusion into W at outer strike point Modelling of ASDEX Upgrade data: First modelling using experimental laboratory/AUG data and measured AUG fluxes Good agreement for outer divertor, further work needed for inner divertor Surface modifications: Blister-like structures observed in laboratory studies and AUG polycrystalline W No blister cap, not hollow (but often/always cavity/crack observed) These are no classical blisters! Naming?