1. Overview of recent work on carbon erosion, migration and long-term fuel retention in the EU-fusion programme and conclusions for ITER V. Philipps a Institute of Plasma Physics, Forschungszentrum Jülich, Association EURATOM-FZJ, 52425 Jülich, Germany A.Kirschner a, H.G.Esser a, A.Litnovsky a, J.P. Coad b,G.F. Matthews b, J.Strachan b, M.Stamp b, M. Rubel c, J. Likonen d, M.Mayer e, V.Rohde e J.Roth e, K.Krieger e, K.Schmid e, A.Kallenbach e, T.Loarer f, E.Tsitrone f, A.Loarte g and contributors to the EFDA-JET Workprogramme, b Culham Science Centre, EURATOM / UKAEA Fusion Association, Abingdon, Oxon OX14 3DB, United Kingdom, c Alfvén Laboratory, Royal Institute of Technology, Association EURATOM-VR, 100 44 Stockholm, Sweden, d VTT Processes, Association EURATOM-TEKES, P.O. Box 1608, 02044 VTT, Finnland, e Max-Planck Institut für Plasmaphysik, EURATOM Association, Garching, Germany, f Association EURATOM-CEA, CEA-Cadarache, Saint-Paul-Lez Durance, France, g EFDA Close Support Unit, Boltzmannstraße 2, 85748 Garching, Germany TEC Introduction EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich

2. ITER Beryllium Tungsten Carbon Long term Tritium inventory and lifetime of plasma facing components are most critical questions for ITER and future power plants Understanding and development of control schemes is the major topic of the EU Task Force on Plasma Wall Interaction (related with the present ITER wall material choice) TEC Introduction EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich in parallel: The full tungsten wall programme in ASDEX-U → following talk by R.Neu

3. Plasma Processes that determine tritium inventory First wall Location and mechanism of erosion Primary erosion processes Long and short range impurity migration Erosion Mixed layer formation Co-deposition with the fuel Deposition Divertor TEC Introduction EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich

4. TEC erosion: chemical erosion in divertor EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich Normalisation of chemical erosion data Ion impact energy Surface temperature Flux Ion Flux ( #/m 2 s) Separatrix Carbon chemical erosion yields near the separatrix very low due to high temperature high fluxes low impact energy Additional decrease of C- erosion by Be-deposition

5. TEC Chemical erosion&Be deposition EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich  CD-band decreases by ~80% for a Be plasma concentration of 0.15 %  Be surface coverage after exposure 87% (AES). Results from Pisces linear plasma device

6. TEC Long range material migration EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich preferential transport to the inner but significant deposition also in the outer divertor AUG W-migration No uniform behaviour of erosion/deposition of outer divertor various other results (e.g. from Be deposition) indicate that transport is exclusively to the inner divertor 13 C: 1.3x10 23 4.8x10 19 1.1x10 21 3.1x10 22 2.7x10 22 Example:JET 13 CH 4 puff in ohmic target plasma 1.2x10 20 3.9x10 20

7. TEC Global material balances: JET and AUG EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich JET: balance between wall sources and inner divertor deposition, no contribution from outer divertor g/campaign AUG: balance needs large net-source in outer divertor or strong sources in main chamber not visible by spectroscopy

8. TEC Short range Material deposition EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich Major progress on characterisation of short range material migration 30 mm Carbon deposition is largely line of sight from the place of origin Majority of carbon (>99%) with high sticking (>0.9), small part (<1%) with low sticking probability (10 -3 ). The same conclusion from C deposition in TEXTOR and AUG pump ducts Sticking Monitors in JET

9. TEC Short range material transport EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich Louvers, QMB detector Post mortem analysis 10 C 1 Be 3 0 0,5 1 1,5 2 2,5 Beryllium-to-Carbon Ratio Be/C 04080120160 Horizontal tile Carbon is transported further (chemical processes) Be stays at primary deposition

10. TEC Short range material transport EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich Carbon deposition on QMB (louver) only for shots with strike point in the vicinity of louver entrance In agreement with ERO Code transport modelling Similar conclusions from AUG QMB data QMB detector Strike point position

11. TEC Introduction EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich A carbon layer is formed on the horizontal tile which is strongly eroded subsequent shots Carbon is transported stepwise to the louver region Short range material transport 12 Reproducible L mode shots strike point 14.3 s 14.7 s 15.0 s ch3 Spectroscopy

12. TEC Understanding of C-Transport EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich Short range C- transport near strike point by chemical erosion No Be transport Strike zones Erosion Deposition Remote area Transport of C to remote areas by a combination of short range transport and varying plasma configurations no Be transport Be C

13. TEC Introduction EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich Pure empirical approach: similar campaign averaged carbon deposition rates in different machines, indicating some machine independence Predictions for ITER

14. TEC EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich Previous predictions 1% chemical erosion inner&outer, Brooks& Kirschner PSI 2002 A scatter of about 10 4 between worst and best assumptions !! Assumption: C-erosion in outer, Be deposition in inner leg S=0.5, moldyn, ERO 6gBe, D/Be= 0.001 S=1, ERO 6gBe, D/Be= 0.001 S=0, moldyn, ERO 6gBe, D/Be= 0.001 New chemical erosion assumptions C-erosion in outer divertor only S=0, moldyn, ERO 50gBe, D/Be= 0.1 Main chamber Be erosion Be deposition in inner divertor only

15. TEC Conclusion + open issues EU PWI Task Force IAEA Nov 2004, Vilamoura, Portugal Institut für Plasmaphysik Assoziation EURATOM-Forschungszentrum Jülich Carbon chemical erosion sources in ITER are smaller than previously assumed, effect of Be deposition on erosion must be clarified further Main chamber is a net material source in general, but more analysis about mechanism and location in present machines is strongly needed Outer divertor behaviour is not uniform. Edge flows are not fully understood and predictions of erosion/deposition in the outer ITER divertor are difficult Due to chemical C-erosion, local C and Be migration in divertor differ largely, Be will be confined largely on plasma facing sides Tritium retention in ITER will be reduced (compared with extrapolation from carbon devices), depends largely on the T-inventory in Be-layers and is difficult to predict more precisely