V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ Ion Cyclotron Wall Conditioning (ICWC) and T removal in TEXTOR A. Lyssoivan, G. Sergienko, V. Philipps, G. Van Wassenhove, R. Koch, H.G.Esser, C.Schulz

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ Motivation Wall conditioning in the presence of permanent magnetic field (inter-shot conditioning) must be developed for /onboard in ITER to allow plasma start up in particular after special events like disruptions, leaks, openings reduce long term T-inventory (T-housekeeping strategy) Ion Cyclotron Wall Conditioning (ICWC) is approved for integration into the ITER baseline using ITER ICRF heating system. Further development of the ITER relevant ICWC scenarios with conventional ICRF antennas is an important and urgent task.

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ R&D on ICWC Optimization ICWC Plasma Production Wall conditioning removal Mechanisms Antenna Coupling Plasma Homogeneity / Extension Homogenity Flux spectrum Fast Ions Generation 1. High Ion Cyclotron Harmonics, =n ci, n>>1 2. Mode Conversion, = ci B T +B V, B V <<B T

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ ICRF plasma can be produced at any B T -field and in any gas mixture used in TEXTOR: He, He+H 2, O 2, O 2 +He, NH 3 +D 2, NH 3 +He =10 cH+ (low field B T 0.2 T): High coupling achieved ( 0.8), density (> m -3 ) and homogeneity ICRF Plasma Characterization

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ = cH+ (BT 2.3 T): less coupling, improvement achieved by proper He/H2 mixtures (mode conversion in He+H2 and overlaying a small vertical magnetic field)

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ AUG: ICRF Plasma Characterization Mode conversion scenario in (He+H 2 )-plasmas: Higher antenna coupling (up to 3 times) Better homogeneity and extension in radial direction Better performance at two frequencies (He+H 2 )-plasma vs He-plasma B T +B V vs B T Vertical magnetic field improves plasma homogeneity in poloidal direction and extends it towards divertor He, f =30 MHzHe+H 2, f =30 MHz He+H 2, f 1 =30 MHz+ f 2 =36.5 MHz BTBT BTBT BVBV B T =2.4 T, B V =0 B T =2.4 T, B V 0.02 T

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ TEXTOR walls were preloaded in D 2 GDC before each cleaning in H 2 +He ICWC plasmas Isotope exchange : D 2 + H = HD

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ ICWC has been tested in TEXTOR in He H 2, D 2 He+ H 2 He+O 2 N 2 + H 2 /D 2 D 2 + NH 3 He+ NH 3 Most effective methods

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ Injected O 2 Maximum allowable pressure determines effectivity He injection O 2 injection CO formation CO outgassing

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ Formed CO

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ ICWC plasmas reliably produced in different gases and Bt For carbon removal, He/O 2 oxygen most effective He/H 2 mixtures best for final cleaning action He/NH 3 has some effectivity, better then H 2 /N 2 (all nitrogen absorbed in TEXTOR) The main constraint with this type of wall conditioning is still the homogeneity (despite the improvements in recent years) AUG found about 25% effectively affected by the cleaning Similar values estimated in TEXTOR Further improvements possible: horizontal magnetic field, several or sweeping frequencies)

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ Proposal for the JET FT 2009: JET Task Force – Fusion Technology Proposal for WP-2009 Development of Ion Cyclotron Wall Conditioning (ICWC) Technique for ITER Proposers:, A.Lyssoivan, V.Philipps, D.Douai, S.Bremond, P.Coad, C.Grisolia, R.Koch, I.Monakhov, J.-M.Noterdaeme, J.Ongena, V.Rohde, G.Sergienko Aim: Develop efficient wall cleaning/conditioning technique for ITER in the presence of permanent high magnetic field using standard ICRH antennas

V.Philipps, SEWG Gas balance and fuel removal, JET, Energy Research – Plasma Physics | Association EURATOM – FZJ