Presentation on theme: "Alberto Loarte 7 th ITPA Divertor Meeting – Toronto 6/9 – 11 – 2006 1 ITER Issue Card PFC-4. Modification of geometry of the divertor PFCs and neutral."— Presentation transcript:
Alberto Loarte 7 th ITPA Divertor Meeting – Toronto 6/9 – 11 – 2006 1 ITER Issue Card PFC-4. Modification of geometry of the divertor PFCs and neutral by-pass leaks A. Loarte, T. Tanabe, H.D. Pacher, A. Kukushkin, G. Pacher
Alberto Loarte 7 th ITPA Divertor Meeting – Toronto 6/9 – 11 – 2006 2 Outline of the ITER Design/Assumptions Divertor design in ITER optimised to meet various requirements and based on B2-Eirene modelling W baffle for R sep > 6 cm Dome eq R sep = 1 cm Separation between cassettes ~ 5 mm Aims of divertor design Allow access to q div peak < 10 MWm -2 for conditions compatible with Q DT = 10 n He / < 6% P main chamber /P div ~ 10 -4 P PFR above-dome / P PFR under-dome ~ 10 Key ingredients of the design : Dome & V-shape near strike point
Alberto Loarte 7 th ITPA Divertor Meeting – Toronto 6/9 – 11 – 2006 3 Issue We know now that : Under a given divertor leak rate main chamber pressure/plasma flux is determined by anomalous transport Effect of septum in JET experiments is weak and only seen in one configuration “Corner” or V-shape effect on detachment seen in JET and ASDEX-Upgrade but quantitative comparison with modelling remains outstanding Modelling of plasma conditions in ITER requires inclusion of non-linear effects as proven by Alcator C-mod modelling Geometry influence with non-linear effects weaker Issues Requirements on divertor neutral leakage, helium pumping, detachment access, etc., and B2-Eirene modelling without non-linear effects have lead to a divertor design which has a restricted plasma configuration flexibility Presence of dome may lead to hydrocarbon deposition in zones of difficult access How long should be the CFC part of the target ?
Alberto Loarte 7 th ITPA Divertor Meeting – Toronto 6/9 – 11 – 2006 4 Actions Review critical effects that influence ITER divertor modelling results Perform experimental/modelling quantitative assessment of above effects Evaluate divertor performance with simplified geometry (i.e. without dome) with validated physics models Evaluate trade-off between increased plasma configuration flexibility and other possible restrictions (reduction of detachment operation window, required pumping for He removal, …) Evaluate pro’s and con’s of presence of dome with respect to hydrocarbon deposition/removal Evaluate effect of increased cassette gap on divertor performance and perform optimisation (leak rate vs. feasibility of installation) Benefits to ITER : Larger device flexibility to explore magnetic configurations Implications in Cost and Schedule : Depending on outcome a simpler divertor would result on a cost saving and no impact on schedule Risks : Loss of diagnostics. Changes to detachment access and its compatibility with H-mode operation ?