Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – ITER Design Review Activities on Steady State and Transient Power Loads in ITER Alberto Loarte European Fusion Development Agreement Close Support Unit – Garching Acknowledgements : EU-PWI TF, ITPA Divertor & SOL Group, ITER and many others

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Requirement to maintain l i 10 MW Analysis of port limiter for ITER (Kobayashi NF 2007) shows : for I p < 6.5 MA q lim max (MWm -2 ) ~ P SOL (MW) Stable ramp-up P tot /P rad ~ P tot > MW P SOL > 8-10 MW q lim max > 8-10 (MWm -2 ) Ramp-up/down Phase

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – New proposed scenario to full bore ramp-up with short ohmic phase (P SOL < 3 MW), early X-point formation & heating Ramp-down in X-point configuration Full bore plasma : large plasma near first wall but low P SOL New Proposed Ramp-up/down Phase

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – All divertor tomakaks measure plasma particle fluxes (II B) to the main wall Extrapolated plasma flux to the main wall in ITER s -1 (1-5 % of div ) Q DT = 10 steady plasma loads (I) Lipschultz IAEA 2000 Lipschultz

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Plasma fluxes predominantly on outer side of first wall Corresponding maximum IIB power densities up to : 5 MWm -2 (Upper X- point) to 1 MWm -2 near outer midplane and 0.4 MWm -2 near inner midplane Q DT = 10 steady plasma loads (II) LaBombard NF 2004

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – C-X particle fluxes vary along wall but C-X power fluxes change only by ~2 C-X particle flux ~ 2 Ion flux s -1 = MWm -2 Q DT = 10 steady C-X and radiation loads P edge > 1.3 P L-H P rad < 0.12 MW m -2

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Time scale of divertor ELM energy flux rise correlated with ion transport time Eich JNM 2005 PIPB 2007 Divertor ELM power fluxes : timescales Plasma conditions affect ELM IR ~ II relation (pre-ELM divertor plasma, W ELM, etc.) JET-Eich-JNM 2003 rise,ELM = s

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – q ELM (t) Large proportion of W ELM arrives after IR smaller T surf for given W ELM down,ELM = 1-2 rise,ELM

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Divertor Area for ELM power Fluxes (I) A div,ELM ~ 3.5 m -2 Broadening ~ 1 Eich, PIPB07 E in,ELM /E out,ELM = 1-2

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Divertor Area for ELM power Fluxes (II) TPF div,ELM ~ 1.0 Divertor ELM load near separatrix ~ toroidally symmetric but strong in/out asymmetries Eich, PRL4 Loarte, PPCF03 from Leonard JNM97 DIII-D

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Tolerable ELM size QSPA experiments on NB31 targets show energy density / MJm negligible erosion erosion starts at PFC corners PAN fibre erosion of flat surfaces after 100 shot significant PAN fibre erosion after 50 shots PAN fibre erosion after 10 shots Tolerable ELM energy density 0.5 MJm -2 + no broadening + 2:1 in/out asymmetry W ELM ~ 1MJ

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Part of W ELM is reaches the main wall PFCs energy flow along filaments Fluxes to main wall during ELMs AUG- Herrmann –PPCF06 highest q wall ELM by filament impact (A. Herrmann, AUG) Example (JET-P. Andrew EPS)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Model of II vs. I B transport during ELMs in agreement with experimental findings: ELM T i > T e far from separatrix (Langmuir Probes + Retarding Field Analyser) Deficit of divertor ELM energy for large ELMs (v r /c s ~( W ELM / W ped ) Radiation) ELM fluxes to Main wall fluxes R Fundamenski - PPCF 2006 R JET- Pitts IAEA 2006 & Fundamenski JNM 2007

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – ELM fluxes to Main wall in ITER (I) ELM power fluxes to PFCs in ITER evaluated by models/empirical extrapolation (input) : W ELM filaments / W ELM, R ELM, V r ELM vs. W ELM (n ped, T ped ), IR ( II ) Controlled ELM W ELM =1MJ f ELM =20-40 Hz Uncontrolled ELM W ELM =20MJ f ELM =1-2 Hz

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – ELM fluxes to Main wall in ITER (II) Average ELM power fluxes to PFCs require knowledge of filament dynamics

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Energy Fluxes to main wall and divertor PFCs during Marfes Pre-disruptive Marfes occur when plasma is already in L-mode In steady state P rad = P inp = MW = MWm -2 Timescale for transient Marfes ~ s (no clear size dependence) Poloidal peaking < 3

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Energy Fluxes during disruptions (I) Energy degradation before thermal quench for resistive MHD disruptions Large broadening of footprint for diverted discharges but small for limiter discharges

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Energy Fluxes during disruptions (II) Timescale (~ R) but large variability ( ms for ITER) Longer timescales in decay phase (> 2 rise phase) Toroidal asymmetries (~2) seen in some cases but poor documentation/statistics Systematic study of in/out asymmetries required

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Proposed ITER specifications (M. Sugihara/M. Shimada) Scenario 2 : unit ( MJ/m 2 ) Energy release at TQ(1/2-1/3)W peak W peak E // near separatrix at outer midplane E // near upper ceiling region (6 cm from 1 st separatrix) E // near lower baffle region (6 cm from 1 st separatrix) E // to divertor plate near 1 st separatrix 280 – 90 (out) 375 – 120 (in) 560 – 280 (out) 750 – 380 (in) =2.5 cm (left), 5 cm (right)Energy deposition time duration = 3-9 ms Energy Fluxes during disruptions (III)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Energy release at TQW peak (325 MJ) E // near separatrix at outer midplane E // near upper ceiling region (5 cm from 1 st separatrix) E // near lower baffle region (5 cm from 1 st separatrix) E // to divertor plate near 1 st separatrix 730 – 365 (out) 375 – 120 (in) =2.5 cm (left), 5 cm (right)Energy deposition time duration = 3-9 ms Proposed ITER specifications (M. Sugihara/M. Shimada) Scenario 4 : unit ( MJ/m 2 ) Energy Fluxes during disruptions (IV)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Major disruptions during limiter phase : (M. Sugihara/M. Shimada) Ip (MA) W peak (MJ) P ; peak energy density (MJ/m 2 ) Most severe assumption : No broadening of deposition width (Kobayashi NF 07) 2 limiter case Energy Fluxes during disruptions (V) If there is no broadening energy fluxes on limiter for disruptions can be similar or larger than for the divertor disruptions in scenario 2

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Energy Fluxes during disruptions (VI) JET ITER Presently proposed ITER specifications based on JET based extrapolations input from other tokamaks is required W 2 = MJ 2 = JET / L-mode JET ( )* L-mode ITER W 3 = W( 2 )-dW/dt| L-mode * 3

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Downward VDE with fast CQ - EM load on BM / DIV by eddy (+halo) current - Heat load on lower Be wall & W baffle Upward VDE with fast CQ - EM load on BM by eddy (+halo) - Heat load on upper Be wall during VDE and TQ Energy Fluxes during disruptions (VII)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Fast H-L transition ( loss in 1-2 s IW contact for up to ~ 5s) can lead to large loads on the inner wall Confinement transients

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Predicted runaway current10 (MA) Energy spectrum of electrons (E0 for exp(-E/E0))12.5 MeV Inclined angle Total energy deposition due to runaway current20 MJ Average energy density deposition1.5 MJ/m 2 Duration of the average energy density deposition100 ms Maximum energy density deposition (end of the plasma termination)25 MJ/m 2 Duration of the maximum energy deposition10 ms Number of eventEvery major disruption These specifications are generally reasonable but physics basis is weak (very poor experimental input) Largest concern energy load by drifted electrons due to formation of X-point Runaway electron fluxes on PFCs (I)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Runaway generation mechanisms for ITER like disruptions conditions studied in detail but runaway losses and dynamics are worse known Runaway electron fluxes on PFCs (I)

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Current profile during runaway discharge peaks (seen at JET) X-point formation in Scenario 2 Runaway electron fluxes on PFCs (II) Smith PoP 2006 EFIT reconstruction by S. Gerasimov

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Runaway electron fluxes on PFCs (III) Significant drift of runaways near upper X-point due to poloidal field null [f(E) = 1/E 0 exp(-E/E 0 ) with E 0 = 12.5 MeV] Angle of impact of runaways on drift orbits at upper X-point < 1.5 o but impact direction mainly toroidal

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT – 10 – Conclusions PID specifications for PFC loads in ITER considered for revision following ITER Design Review Process New specifications will be used for modification to existing design reasonable range and upper boundaries for loads have to be provided Input and constructive criticisms from EU-PWI TF and ITPA are gratefully acknowledged