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Deuterium Inventory in ASDEX Upgrade

Deuterium Inventory in ASDEX Upgrade M. Mayer 1 , V. Rohde 1 , G. Ramos 2 , E. Vainonen-Ahlgren 3 , J. Likonen 3 , A. Herrmann 1 , and ASDEX Upgrade Team 1 Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching, Germany

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Deuterium Inventory in ASDEX Upgrade

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  1. Deuterium Inventory in ASDEX Upgrade M. Mayer1, V. Rohde1, G. Ramos2, E. Vainonen-Ahlgren3, J. Likonen3, A. Herrmann1, and ASDEX Upgrade Team 1 Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching, Germany 2 CICATA-Qro, Instituto Politécnico Nacional, Querétaro, México 3 Association EURATOM-TEKES, VTT Processes, Espoo, Finland • Deuterium inventory – Inner, outer divertor – Gaps between tiles – Remote areas – Upper divertor, limiter, …

  2. Wall areas and analysis methods upper divertor • Analysis methods • NRA D(3He,p)a - 1000 keV: D inventory in 2 µm - 2500 keV: D inventory in 10 µm • Marker stripes for RBS - Deposition of B, C (talk on 9.5.2007) • SIMS • Data for 2002-2003 and 2004-2005 • campaigns • Carbon dominated machine upper PSL inner heat shield ICRH limiter lower PSL inner divertor pump duct outer divertor roof baffle

  3. 6A 3B 3A 6B 5 2 4 9B 1B 1A 10 9C 9A Divertor 2002–2003 Inner divertor - Deposition on all tiles Roof baffle - Deposition directly opposite of inner strike point - Otherwise small D inventories Outer divertor - Erosion area, small D inventories - Localized deposition in divertor corner

  4. Inner divertor 2002–2003 and 2004–2005 2004–2005, 3060 s 2002–2003, 4860 s • D/(B+C) = 0.4 is upper limit (and often typical) for inner divertor tiles • Observed D/(B+C) may be lower, B+C more robust indicator for D inventory

  5. Inner divertor gaps 2004–2005 • Exponential decay with l = 1–2 mm (plasma-exposed) and l = 20–30 mm • Inventory predominantly on plasma-hit areas

  6. 6B 5 Inner divertor gaps 2004–2005 (2) D-inventory Tile in gap without gap [µg] [µg] 6B 130 200 5 770 940 Identical inventory with and without gap  Inner divertor gaps do not increase inventory, but change spatial distribution  As expected for high-sticking particles

  7. 3B 3A 2 1B 1A 10 Outer divertor 2002–2003 and 2004–2005 2004–2005 2002–2003 • Net erosion in most of outer divertor, resulting in small inventories • Small deposition area in lower divertor corner •  Material probably originates from outer strike point •  Inventory can be minimised by strike-point sweeps

  8. Outer divertor gaps 2004–2005 • Exponential decay with l = 20–30 mm • Inventory very small, no difference between plasma-hit and plasma-shadowed side

  9. Below roof baffle 2002–2003 • Maximum inventories in line-of-sight to strike points • Small inventories at shadowed areas •  Layer deposition by particles with high (~ 1) sticking probability

  10. Pump duct 2000–2001 • Very small inventory in 2000–2001 • Also very small in 2001–2002, maximum 5×1015 D-atoms • Flange from pump duct 1996-2006: 2×1015 D-atoms •  Negligible inventory in pump ducts •  Low sticking species reach pump duct, but have only very small contribution to D inventory

  11. a1 I1 ? 86I PSL Upper divertor 2003–2004 • Small inventory, compared to lower divertor • Inventory mostly due to boronizations • Erosion at strike points, deposition towards inner and outer side

  12. ICRH limiter B 1 4 8 Auxiliary limiter 2005–2006 • Complex distributions • Low amount of D, small area •  Small inventory

  13. Deuterium retention in 2002–2003 Retention Fuelling from (B+C), assuming D/(B+C)=0.4 Long-term D retention 3–4% of fuelling Majority on divertor tiles (50-60%), followed by remote areas (20%) Gas balance (Mertens 2003): 10–20%Marginal agreement, taking error bars into account

  14. Reserve slides

  15. Outer divertor gaps 2004–2005 • Exponential decay with l = 20–30 mm • Inventory very small, no difference between plasma-hit and plasma-shadowed side

  16. Outer divertor gaps (2) • Max D inventory after 2004–2005 campaign: 6×1017 D-atoms in 1000 discharges • Castellated W (Krieger 2006): 3×1017 D-atoms in 3 discharges •  Difference by 2 orders of magnitude • – Exposure of castellated W in C environment, and tile 2 in W environment?– Re-erosion by atomic H, nonlinear growth? Krieger 2006

  17. Predictions for ITER ITER fuelling: 50 g T 2 g D-retention for 4% retention fraction Net deposition and net erosion areas predicted at inner and outer ITER target Not observed in today’s machines (different plasma parameters) ITER predictions are based oncalculations which are not wellbenchmarked AUG offers unique data base A. Kirschner 2006

  18. W coverage in AUG 2002 – 2006 Step by step replacement of C offers unique possibility to identifynet carbon sources Neu 2007

  19. 2002 - 2003 2003 - 2004 2004 - 2005 2005 - 2006 C-concentration in plasma • Data for ‘standard’ H-mode • Decrease of core C-concentration by factor ~2 • Scatter of data due to • Boronizations • Discharge history • Operational imperfections • … • Data from 2002–2003 and 2004–2005 •  Carbon dominated machine Kallenbach 2007

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