v.philipps, sewg gas balance and fuel removal, jet, 22.7.08 energy research – plasma physics |...
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V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 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, 22.7.08 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, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
R&D on ICWC Optimization
ICWC Plasma Production Wall conditioning removal Mechanisms
AntennaCoupling
GRFplRF PP
PlasmaHomogeneity/ Extension
• Homogenity• Flux spectrum • Fast Ions Generation
1. High Ion Cyclotron Harmonics, =nci, n>>12. Mode Conversion, = ci
BT+BV, BV<<BT
V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
ICRF plasma can be produced at any BT-field and in any gas mixture
used in TEXTOR: He, He+H2, O2, O2+He, NH3+D2, NH3+He
=10cH+ (low field BT0.2 T): High coupling achieved (0.8), density (>21017 m-3) and homogeneity
ICRF Plasma Characterization
V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.60
1
2
3
4
5
6
7TEXTOR- (He+H2)-plasma +Bv
- (He+H2)-plasma
- He-plasma
HD
Rem
oval
Rat
e[1
0
mol
/(skW
)]16
BT [ T
=cH+ (BT2.3 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, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
AUG: ICRF Plasma Characterization
Mode conversion scenario in (He+H2)-plasmas:
Higher antenna coupling (up to 3 times)
Better homogeneity and extension in radial direction
Better performance at two frequencies
(He+H2)-plasma vs He-plasma
BT+BV vs BT
Vertical magnetic field improves plasma homogeneity in poloidal direction and extends it towards divertor
He, f=30 MHz He+H2, f=30 MHz He+H2, f1=30 MHz+f2=36.5 MHz
I II III
BT BT
BV
BT=2.4 T, BV=0 BT=2.4 T, BV0.02 T
V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
TEXTOR walls were preloaded in D2 GDC before each “ cleaning” in H2+He ICWC plasmas
Isotope exchange : D2 + H = HD
V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
ICWC has been tested in TEXTOR in
He
H2, D2
He+ H2
He+O2
N2+ H2/D2
D2+ NH3
He+ NH3
Most effective methods
V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
Injected O2
Maximum allowable pressure determines effectivity
He injection
O2 injection CO formation
CO outgassing
V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
Formed CO
V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
ICWC plasmas reliably produced in different gases and Bt
For carbon removal, He/O2 oxygen most effective
He/H2 mixtures best for final cleaning action
He/NH3 has some effectivity, better then H2/N2 (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, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
Proposal for the JET FT 2009:
JET Task Force – Fusion Technology Proposal for WP-2009Development of Ion Cyclotron Wall Conditioning (ICWC) Technique for ITERProposers:, 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, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ
V.Philipps, SEWG Gas balance and fuel removal, JET, 22.7.08 Energy Research – Plasma Physics | Association EURATOM – FZJ