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Issue card: wall conditioning V. Philipps, A. Lyssovan

Issue card: wall conditioning. EU PWI Task Force. V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006. Issue card: wall conditioning V. Philipps, A. Lyssovan. Issue card: wall conditioning. EU PWI Task Force. V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006.

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Issue card: wall conditioning V. Philipps, A. Lyssovan

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  1. Issue card: wall conditioning EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 Issue card: wall conditioning V. Philipps, A. Lyssovan

  2. Issue card: wall conditioning EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 • Background: present machine experience show that appropriate wall conditioning can be crucial to maintain the • machine availability (the sensitivity for non sustained breakdowns increases with machine size (see last ITPA discussion about ITER start up) → ITER start up critical under non ideal wall conditions in particular after events like disruptions, leaks, breakdowns etc. • provide adequate wall conditions for special operational regimes. • ITER GDC only if toroidal magnetic field is switched off, thus only after major interventions (no intershot, overnight conditioning) • ITER will need a reliable wall conditioning technique which can be used in the presence of the toroidal magnetic field • → ECR and/ or ICR-DC conditioning must be used.

  3. Issue card: wall conditioning EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 ECR and ICRH wall conditioning have been explored and qualified in present experiments ( Alcator C ,HT7, Textor, TS,, LHD and others) as wall condition technique for cleaning and for coating The ITER ICH&CD system should be reviewed to accommodate the requirements for wall conditiong plasmas Differ from those of plasma heating since they require Lower power and higher gas pressures (ICRH) Variable field or frequency ( ECR)

  4. Issue card: wall conditioning EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 Resistance exists for using the main (and single) ITER ICRH antenna for wall conditioning due to difficulty to protect the ICH&CD system against arcing at lower power and higher gas pressures (also formulated in the ITER Issue Card “5.2-13 Wall conditioning in ITER” submitted by Scimada Michiya on September 6, 2006 ) Two strategies : 1. Use the main ICRF antenna, but : the antenna will be designed according to heating and current drive purposes, one ICRF antenna should take over tokamak start-up assistance + plasma heating and current drive during shots + wall conditioning between shots. 2. Prepare dedicated ICRF antenna (s) for routine wall conditioning in between shots, preferred solution for ICRH experts (R. Koch, A. Lyssovan et al)

  5. Issue card: wall conditioning EU PWI Task Force V.Philipps, ITPA Div and SOL, 6.-9. 11. 2006 Some literature: Ion cyclotron conditioning with strong magnetic field in LHD N. Ashikawa a,∗, S. Masuzaki a, K. Nishimura a, T. Seki a, K. Saito a, R. Kumazawa a, T. Mutoha, A. Sagara a, N. Ohyabua, J.S. Hub, Y. Zhaob, Fusion Engineering and Design (2006) Low loop voltage start-up of the TEXTOR-94 discharge with ICRF and/or NBI assistance R.Koch1, A.Lyssoivan1, E. de la Cal and E. Gauther 2005 PPCF 47 197 more details can be find in: principal possibility for ICRF-DC and ICRF assisted start-up for ITER with ITER ICRF antenna: A.Lyssoivan et al. Final Report on ITER Design Task D350.2 (LPP-ERM/KMS Report No 114, 1998

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