Outline of the ITER Design/Assumptions
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Alberto Loarte 7th ITPA Divertor Meeting – Toronto 6/9 – 11 – 2006 1
ITER Issue CardSTART-UP-1. Limitations to plasma start-up
and optimize shaping flexibility for ITER Scenarios
G. Federici, A.Loarte, H. D. Pacher, G. W. Pacher, A.
Kukuskhin, T. Luce, A. Sips, A. Leonard, R. Stambaugh,
C. Kessel
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Alberto Loarte 7th ITPA Divertor Meeting – Toronto 6/9 – 11 – 2006 2
Outline of the ITER Design/Assumptions
limiter X-point (6.5 MA)
Plasma breakdown and ramp-up and ramp-down in ITER is carried out in limiter configuration
To ease maintenance limiters are positioned in main horizontal ports Be is chosen as limiter PFC 2 limiters are required for sufficient power
handlingX-point limiter (9.5 MA)
Ramp-up scenario designed for fast current penetration
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Alberto Loarte 7th ITPA Divertor Meeting – Toronto 6/9 – 11 – 2006 3
Issue We know now that : Despite complex connection length pattern power load on limiters is reasonably well described by simple exponential decay For reference ITER start-up scenario 2 with <ne>/nGW ~ 0.2 qlimiter,max ~ 3 MWm-2 in ramp-up
There is little margin in changing ne in ramp-up (radiative collapse) and limited capability for additional heating during ramp-up Relative alignment of limiters is difficult to between than few mm Early X-point transition at 3.5 MA but can lead to loss of half of flat top length
Flexibility of ramp-up scenarios in ITER is limited by PFCs power handling and flux consumption unreasonable limits to scenario development
Psol = 1MW
Psol = 3MW
Psol = 2 MW
Psol = 2MW
Psol = 6 MW
Psol = 3 MW
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Alberto Loarte 7th ITPA Divertor Meeting – Toronto 6/9 – 11 – 2006 4
Actions
Review/complete calculations of limiter power loading in present ITER ramp-up/ramp-down scenarios
Develop scenarios/analyse heating requirements for qmin > 1 operation
Study alternative limiter configuration more limiters/different PFM/poloidal limiters with limited power handling (~ 0.5-1.0 MWm-2 ) located at inner or outer wall, etc.
Investigate early X-point formation (~ 3MA or lower) from outer limiter and from inner wall, divertor dome and implications for PF system
Benefits to ITER : Larger device flexibility to explore different q profiles. If breakdown from inner wall is adopted there could be a gain in Volt-seconds. If early X-point transition
achieved large control of ramp-up conditions by heating/fuelling/pumping
Implications in Cost and Schedule : Depending on outcome port limiters could be eliminated with a corresponding saving. This would be probably offset by a more expensive PF system
Risks : More delicate PF system (if NbSn needed) and weakness of poloidal limiters to transient (~ s) plasma contact