Edge Plasma Energy and Particle Fluxes in Divertor Tokamaks

Transcription

1 Edge Plasma Energy and Particle Fluxes in Divertor Tokamaks Alberto Loarte European Fusion Development Agreement Close Support Unit - Garching Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

2 1. Introduction Outline of the Talk Edge Power and Particle Fluxes : Divertor SOL 2. Steady State Energy and Particle Fluxes Divertor Radiation and Particle Control Main Chamber Particle Fluxes 3. ELM Transient Energy and Particle Fluxes Bulk Plasma Energy Losses, ELM Divertor Energy Fluxes & Interaction with Main Chamber Walls 4. Conclusions Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

3 Introduction B r B r Open Field Lines in Tokamaks Transport (~ 50 m) >> Transport (~ 1 cm) Localised Interaction in Plasma Facing Components Control of Energy and Particle Fluxes (He) on PFCs is crucial for development of Fusion Edge Plasma rich Physics: Transport B r & B r, neutral Species,Plasma-Material Interaction, Improvement in Understanding of Edge Plasma Physics : Models + Diagnostics Large Energy and Particle Fluxes on PFCs + Control of Interaction Region by PFCs Design and Limiter Plasma Diverted Plasma JET P SOL ~ 10 MW A div ~1.5 m 2 ITER P SOL ~ 100 MW A div ~ 3.5 m 2 B r θ Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

4 Divertor SOL a) Target Impurity Source separated from Main Plasma b) λ 0 λ 0 λ λ << Distance X-point Target D, C, D2, Large Ionisation/Radiative Losses T plasma,divertor << T plasma,sol Low q div c) Large Neutral Densities (Divertor Closure) Good D 2 and He Exhaust d) Separate Divertor Power Handling and Particle Control Problem (Geometry) e) Low T plasma.divertor Atomic and Molecular Physics C x D y Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

5 Steady State Energy and Particle Fluxes Divertor Geometry Low T e at divertor Carbon Chemical Sputtering Large P rad div in wide P INP Range Results are well understood by 2-D modelling (B2-Eirene) Schneider, R., et al., 17 th IAEA Conference, Yokohama, 1998 Kallenbach, A., et al., Nucl. Fusion 39 (1983) 901 Coster, D. et al., 27 th EPS, Maastricht, 1999 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

6 Divertor Neutral Particle Fluxes Optimising Divertor Geometry reduces Neutral Escape through Divertor Plasma Increased Divertor Closure Larger Divertor Pumping Divertor Closure = S ion outside-divertor /S ion total Common Result to all Divertor Experiments (AUG, C-mod, DIII-D, JET, JTF-2M JT-60U) JET Team, Nuclear Fusion 39 (1999) 1751 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

7 SOL Transport Main Chamber Recycling (I) Neutral Pressure in main Chamber : Divertor Leakage + Main Chamber Recycling low n 0 in Main Chamber low C-X and possibly reduced Erosion C-mod : by pass open lower P div & same P main P main independent of P div or (f leak x P div )~ constant? Pitcher, C.S., et al, Phys. Plasmas 7 (2000) 1894 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

8 SOL Transport Main Chamber Recycling (II) Larger Divertor Closure Decrease of Neutral Pressure in main Chamber but minimum n 0 in main Chamber (Mk IIa/p & Mk IIGB) set by anomalous Transport (ELMs?) S pump eff ~ 115 m 3 /s S leak ~ 305 m 3 /s Divertor Main Chamber S pump eff ~ 120 m 3 /s S leak ~ 114 m 3 /s Mark IIa/p P div Mk IIa:P div Mk IIa/p:P div Mk IIGB (L-mode) (H-mode) P main Mk IIa:P main Mk IIa/p:P main Mk IIGB (L-mode) (H-mode) Altmann, H., et al., 17 th SOFE, San Diego 1997 Horton, L., et al., Nucl. Fusion, 39 (1999) 1 Maggi, C., et al., 26 th EPS, Maastricht, 1999 Loarte, A., et al., Plasma Phys. Control. Fusion 43 (2001) R183 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

9 SOL Transport Main Chamber Recycling (III) long Tails in SOL n e & T e seen in many Experiments ASDEX Upgrade T e n e p e Neuhauser, J., et al., Plasma Phys. Control. Fusion 44 (2002) 855 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

10 SOL Transport Main Chamber Recycling (IV) SOL Turbulence : large Transient Events large Gradients & fast Propagation Speeds ( ne, SOL ne, SOL ) ΓExB PDF Γ V ExB (m/s) σ n e, SOL ExB Hidalgo, C., et al. 15 th PSI, Gifu, 2002 Physics of λ SOL n ~ 1 cm v anomalous ~ m/s (D ~ m 2 /s) SOL n e, SOL v V anomalous ~ 200 m/s Large Large = Diffusion τ ~ 50 µs (& τ II ~ 1 ms) SOL Transport Main Chamber Erosion + required Divertor Closure SOL Turbulence Simulation Codes Comparison with Measurements is now possible Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

11 ELM Transient Energy and Particle Fluxes H-mode Confinement is characterised by ETB and Type I ELMs Type I ELMs are triggered when MHD limit is exceeded Typical W ELM ~ 5 % W dia ~ 15 % W ped Regimes with high Pedestal Pressure and small ELMs exist in JT-60U and ASDEX Upgrade but ITER Confinement is based on Type I ELMy H-mode Kamada, Y., Plasma Phys. Contr. Fus. 42 (2000) A247, Stober, J., et al. Nucl. Fusion 41 (2001) 1123 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

12 ELM Energy Losses (II) Type I ELM Energy Loads are of Concern for ITER Divertor Lifetime Bulk Plasma Type I ELM Energy Losses : Conduction & Convection W ELM /W ped decreases with increasing n e,ped because of T e,ped /T e,ped Loarte, A., et al., 28 th EPS Conf & Plasma Phys.Contr.Fus.(2002), Leonard, A., et al., Plasma Phys.Contr.Fus. 44 (2002) 945 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

13 ELM Energy Losses (III) Multimachine Evaluation of W ELM indicates that ν* ped is an ordering Parameter for ELM Energy Losses W ELM /W ped JET Delta_0.25_3.5MA/3.0T JET_Delta=0.33_2.5MA/2.7T JET_Delta_0.33_Before_Pellet_2.5MA/2.7T JET_Delta_0.33_At_Pellet_2.5MA/2.7T JET LT Ar_2.5MA/2.4T JET Delta_0.33_1.9MA/2.0T JET Delta_0.41_2.5MA/2.7T_Squareness JET_Delta_0.50_2.5MA/2.7T JET HT Ar_2.5MA/2.4T JT 60U DIII D_LT_PSI DIII D_HT PSI ASDEX U W ELM /W ped JET Delta_0.25_3.5MA/3.0T JET_Delta=0.33_2.5MA/2.7T JET_Delta_0.33_Before_Pellet_2.5MA/2.7T JET_Delta_0.33_At_Pellet_2.5MA/2.7T JET LT Ar_2.5MA/2.4T JET Delta_0.33_1.9MA/2.0T JET Delta_0.41_2.5MA/2.7T_Squareness JET_Delta_0.50_2.5MA/2.7T JET HT Ar_2.5MA/2.4T JT 60U DIII D_LT_PSI DIII D_HT PSI ASDEX U 0.05 ν* ITER 0.05 ITER ν * ped n e,ped /n Greenwald Not a W ELM Scaling Development of ELM Energy Loss Physics Model : 1) ν* ped MHD Trigger of ELM (Bootstrap Current) 2) ν* ped B Energy/Particle Transport during ELM 3) ν* ped II B SOL Energy/Particle Transport during ELM Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

14 ELM Divertor Power Fluxes (I) Time Scale for Divertor Power Flux Correlated with T e,ped T e,ped ~ 1.6 kev JET Low Density Eich PSI 2002 JET. Loarte PPCF 2002 T e,ped (a.u.) MHD Inner Midplane (a.u.) τ MHD Outer Midplane (a.u.) Soft X-Ray Inner Divertor (a.u) MHD duration of ELM Event well correlated with X-ray Bremsstrahlung Emission from the Divertor Target [Be(250µm)] T e > kev] Lingertat, J., et al., Jour. Nuc. Mat (1997) 402 Gill, R., et al., Nucl. Fusion 38 (1998) 1461 D α Midplane (a.u.) D α Inner divertor (a.u.) Time (ms) D α Outer divertor (a.u.) Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

15 ELM Divertor Power Fluxes (II) At lower T e,ped τ ELM IR much longer than MHD duration of ELM and of hot Electron Energy Pulse on Divertor T e,ped ~ 0.9 kev JET Medium Density Eich PSI 2002 JET. Loarte PPCF 2002 T e,ped (a.u.) MHD Inner Midplane (a.u.) MHD Outer Midplane (a.u.) Soft X-Ray Inner Divertor (a.u) τ D α Midplane (a.u.) D α Inner divertor (a.u.) Sheath vs. Core B impedance to Energy Loss? D α Outer divertor (a.u.) Time (ms) Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

16 Duration of Divertor ELM Energy Pulse correlated with II B Ion Transport (~ kinetic Simulations) ELM Divertor Power Fluxes (III) Front τ = 2πRq 95 c s, ped Lingertat, J., et al., Jour. Nuc. Mat (1997) 402 Herrmann, A., et al., 15 th PSI Conference, Gifu, 2002 Loarte, A., et al., 15 th PSI Conference, Gifu, 2002 Eich, T., et al., 15 th PSI Conference, Gifu, 2002 Bergmann, et al., Nucl. Fusion 2002 Jachmich, et al., 28 th EPS Conf., Madeira, 2001 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

17 ELM Divertor Power Fluxes (IV) SOL Width for Energy Flux during ELM similar to between ELMs χ χ χ χ λ (cm) ELM ASDEX Upgrade Herrmann Low delta High delta λ p between ELMs (cm) between _ ELM Herrmann, A., et al., 15 th PSI Conference, Gifu, 2002 Lingertat, J., et al., Jour. Nuc. Mat (1997) 402 Loarte, A., et al., 15 th PSI Conference, Gifu, 2002 Eich, T., et al., 15 th PSI Conference, Gifu, 2002 Relative Probability Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching Despite narrow W ELM div / W ELM ~ 0.6 ASDEX Upgrade. Data from Herrmann EPS 1997 W DIV ELM/ W ELM Where does the Rest of W ELM go? 1) Toroidal Asymmetries 2) Main Chamber 3) Transiently enhanced P RAD ELM

18 ELM Energy Losses to Main Chamber (I) JET : Divertor ELM missing Energy correlated with ELM size (<n e >) JET - Eich JET - Eich High n e W ELM div / W ELM Bulk but possibly P ELM Rad, div High n e ELMs : a) More toroidally symmetric b) W ELM Main Chamber / W ELM Bulk Eich, et al., T., 15 th PSI Conference, Gifu, 2002 Herrmann, A., et al., 15 th PSI Conference, Gifu, 2002 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

19 ELM Energy Losses to Main Chamber (II) Divertor ELM missing Energy Fast radial ELM Particle Transport (?) For large ELM Events (~ di sat /dr) v r,elm >1 km/s JET- Large ELM Plasma Fluxes in far SOL Low n e Type I ELMs High n e Type I ELMs Type III ELMs Loarte, A., et al., Nucl. Fusion 38 (1998) 331 Hidalgo, et al., 29 th EPS Montreux 2002 Counsell, G., et al., 15 th PSI Conference, Gifu, 2002 τ τ ELM 10µ s Energy ~ µ s Radial ELM Propagation in MAST ~ 1500 m/s Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

20 Conclusions (I) Poloidal Divertors have successfully demonstrated Control of Power and Particle Fluxes in Tokamaks Understanding of parallel Transport in Divertor SOLs is at an advanced Level SOL Flows & Drifts Collisionless Ion Transport in SOL Understanding of perpendicular SOL Transport is at a much more primitive Stage (difficulty of Measurements) SOL Diffusive Particle Transport vs. Convective Blobs Physical Parameters that determine SOL Transport Convective SOL Energy Transport Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

21 Conclusions (II) Type I ELMs Divertor Energy Loads are of Concern for the Lifetime of the ITER Divertor. Physics based Extrapolation is still uncertain Type I ELM Energy Losses determined by n e,ped & T e,ped Bulk Plasma ELM conductive Energy Losses decrease with ν* ped ELM convective Energy Losses independent of ν* ped Physical Process that leads to ν* ped Dependence? Extrapolation of pure convective Type I ELMs? Physics behind ELM Particle Losses (MHD?) ELM Divertor Energy Deposition Time is determined by T e,ped Is T e,ped Dependence due to Transport in ELM ergodised Layer or to Formation of high Energy e - Sheath (or both)? Radial Particle Fluxes Erosion of Main Chamber Walls ELM Energy Split Divertor/Main Walls Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

22 Limiter SOL Scrape-off Layer Plasma Physics in Limiter Discharges is relatively Simple : a) λ Low Re-ionisation of D 0 0 D ~ 10 cm in SOL b) λ Sizeable Re-ionisation of C 0 0 C ~ 1 cm in SOL c) λ D, C D mm Molecules are Re-ionised in SOL 2 λ x y ~ d) Low SOL Ionisation/Radiation T plasma, limiter ~ T plasma,sol PFC Alignment + λ SOL Maximum Area of Limiter Γ D 0,limiter ~ 1/A limiter Power Handling vs. Particle Control? Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

23 Divertor Geometry and Fluxes (Ia) B θ 0 near X-point + Divertor Target Geometry determine Γ div & Γ div JET Experiments : Ohmic and ELM-free H-mode Loarte, A., et al., Nucl. Fusion 32 (1992) 681 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

24 Divertor Geometry and Fluxes (IIa) Diffusion in Private Flux Region (PFR) is a unique Divertor Process DIII-D Experiments : ELMy H-mode Γ div Increases with X-point height Decreasing Flux expansion and Increasing angle of incidence No Diffusion in PFR Diffusion in PFR accounts for ~2 reduction in when going from AUG-Div I AUG-Div II div,sep P Lasnier, C. et al., Nucl. Fusion 38 (1998) 1225 Loarte, A., Contrib. Plasma Phys. 32 (1992) 468. Schneider, R., et al., J. Nucl. Mat (1999) 175 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

25 Steady State Energy and Particle Fluxes(Ia) Divertor Plasma Conditions Characterised by Behaviour of Ion Flux a) Low Recycling Divertor J div ~ e, SOL T div Constant b) High Recycling Divertor J div ~ n n 2 e, SOL T div 1 2 ne, c) Detached Divertor J div n x e, SOL SOL ( x > 0) Degree of Detachment D.o.D > 1 Detachment T div ~ y n e, SOL > ( y 0) Shimomura, Y., et al., Nucl. Fusion 23 (1983) 869 Keilhacker, M., et al. Phys. Scr. T2/2 (1982) 443 Loarte, A., et al., Nucl. Fusion 38 (1998) 331 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

26 SOL Pressure Balance is maintained in Low/High Recycling Divertors but not in Detached Divertors (AUG, DIII-D, C-Mod, JET, JT-60U) EDGE2D/U-NIMBUS JET Divertor Particle Fluxes (Ia) Gas Target Physics : a) D + - D, D + -D 2 collisions (Momentum Loss) b) D + -e - Recombination (Particle Sink) c) Divertor Geometry Affects Detachment Onset Borrass, K., et al., J. Nucl. Mat (1997) 250 Borrass, K., Czech, J. Phys. 48/S2 (1998) 13 Loarte, A., J. Nucl. Mat (1997) 118 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

27 Divertor Energy Fluxes (Ia) High Recycling Divertor Transport Electron Conduction Detached Divertor Transport Convection DIII-D Leonard, A.W., et al., Phys. Rev. Lett. 78 (1997) 4769 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

28 Divertor Neutral Fluxes (Ia) 2-D Edge Plasma Models (EDGE2-D/NIMBUS & B2-Eirene) used to understand Neutral Transport in Divertor : Ballistic versus Diffusive Transport Ballistic Transport Strong Dependence of Pumping on Divertor Plasma Position Diffusive Transport (Multiple Wall Collisions and C-X) Weak Dependence of Pumping on Divertor Plasma Position DIII-D JET Cryo-Pump Loarte, A., et al., 24 th EPS, Berchtesgaden 1997 Loarte, A., et al., Plasma Phys. Control. Fusion 43 (2001) R183 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

29 Divertor Neutral Fluxes (IIa) Noble Gases Transport has large Ballistic Component Noble Gas Enrichment in Pumping Plenum dominated by Geometry and Ionisation mean free Path Div I Ne reaches Pump He escapes Divertor Div II Ne cannot reach Pump He reaches Pump Divertor Geometry can be optimised for He pumping versus Ne/Ar used for P rad Control Schneider, R., et al., 17 th IAEA Conference, Yokohama, 1998 Bosch, H. S., et al., Jour. Nuc. Mat (1999) 462 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

30 Divertor Asymmetries (Ia) Toroidal Geometry leads to Power Asymmetries T e,div out > T e,div in Toroidal in/out Asymmetry & Flow Pattern 1) Larger Flux through Outer Half of Tours 2) Power Asymmetry Inner Divertor Detachment Inner to Outer Neutral Flux ASDEX-Upgrade Kallenbach, A., et al., Nucl. Fusion 39 (1983) 901 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

31 Divertor Asymmetries & Flows (Ia) Direction of B φ affects Inner/Outer Divertor Imbalance and SOL Flows JT-60U - Midplane B φ negative B φ reversal Effects on Inner Outer Divertor T e C-mod B φ positive Asakura, N., et al., Phys. Rev. Lett. 84 (2000) 3093 Hutchinson, I., et al., Plasma Phys. Control. Fusion 38 (1996) A301 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

32 Divertor Asymmetries & Flows (IIa) SOL Drifts SOL Flows Plasma Core Momentum Diffusion SOL Flows Erents S.K., et al., Plasma Phys. Control. Fusion 42 (2000) 905 Comparison 2-D Edge Modelling Codes (with Drifts) Experiment Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

33 SOL Transport Main Camber Recycling (Ia) Larger Divertor closure decrease of Neutral Pressure in main Chamber but minimum n 0 in main Chamber (Mk IIa/p & Mk IIGB) set by anomalous Transport (ELMs?) S pump Eff ~ 115 m 3 /s S leak ~ 305 m 3 /s S pump Eff ~ 120 m 3 /s S leak ~ 127 m 3 /s Mark IIa/p P div Mk IIa:P div Mk IIa/p:P div Mk IIGB (L-mode) (H-mode) P main Mk IIa:P main Mk IIa/p:P main Mk IIGB (L-mode) (H-mode) Altmann, H., et al., 17 th SOFE, San Diego 1997 Horton, L., et al., Nucl. Fusion, 39 (1999) 1 Maggi, C., et al., 26 th EPS, Maastricht, 1999 Loarte, A., et al., Plasma Phys. Control. Fusion 43 (2001) R183 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

34 Collisionless Ions in SOL(I) Evidence for high Energy ions in SOL of JET SOL H-modes exists for a long Time JET-Low n e H-modes P ion /P electron > 5 Ion Orbit Simulations JET Mk II GB Loarte, A. PhD Thesis & Jour. Nuc. Mat (1995) 606 Fundamenski, W., et al., Plasma Phys.Control.Fusion 44 (2002) 761 Physics Validation for ITER required : ν* ped <<1 but ν* C-X div >>1 Ion Losses to inner/outer Divertor depend : 1) E r in SOL 2) Pedestal Plasma Collisionality and Pedestal width 3) C-X in the divertor Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

35 Collisionless Particles in SOL (IIa) ASCOT Calculation Results depend on : 1) E r in SOL 2) Pedestal Collisionality and width 3) C-X in the divertor Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

36 ELM Energy Losses (Ia) ITER Divertor Lifetime determined by Type I ELMs Energy Loads leading to Ablation/Melting W ITER ped ~ 100 MJ Federici, G., 15 th PSI Conference, Gifu Japan 2002 A div ITER ~ 5 10 m 2 W ped ITER < 5-10 MJ Extrapolation of present Results to ITER : o Diagnostics that allow good Experimental Characterisation ELM Energy/Particle Losses o Systematic Experiments for Type I ELM Characterisation o Development of Physics Model for Type I ELM Energy and Particle Losses Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

37 ELM Energy Losses (IIa) Minimum Type I ELMs (Purely Convective) can occur at high density JET Normal Type I ELM JET Minimum Type I ELM Pulse No: Time: Separatrix Radius ms after ELM 2500 Pulse No: Time: Separatrix Radius 2000 Pedestal Radius ms after ELM T e (ev) µs after ELM T e (ev) Pedestal Radius 350 µs after ELM Before ELM Major radius, R (m) JG c Before ELM Major radius, R (m) JG c Loarte, A., et al., 43 rd APS Conf & Plasma Phys.Contr.Fus.(2002), Leonard, A., et al., Jour. Nuc. Mat (2001) 1097 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

38 T e (ev) ELM Energy Losses (IIIa) Decrease of W ELM with <n e > due to T e,ped /T e,ped decrease not tolarge reduction of ELM affected volume JET. Loarte + JT 60U. Chankin JET_53185 low <n e > b_elm JET_53185 low <n e > a_elm JET_53186_medium <n e > b_elm JET_53186_medium <n e > a_elm JET_53190_high <n e > b_elm JET_53190_high <n e > a_elm JT 60U_37847_low <n e > b_elm JT 60U_37847_low <n e > a_elm ρ JET. Loarte + JT 60U. Chankin T e ELM / Te ELM max JET_53185 low <n e > JET_53186 medium <n e > JET_53190 high <n e > JT 60U_37847 low <n e > ρ Loarte, A., et al., 15 th PSI Conference, Gifu 2002 Loarte, A., et al., Plasma Phys. Contr. Fus. (2002) Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

39 ELM Particle Losses (I) Bulk Plasma ELM Particle Losses (& B Energy Convection) not obviously correlated with T e,ped or n e,ped ( MHD Nature of ELM?) DIII-D JET- Large ELM Plasma Fluxes in far SOL Low n e Type I ELMs Pedestal Pressure Degradation High n e Type I ELMs Type III ELMs Leonard, A., et al., Plasma Phys. Contr. Fus. 44 (2002) 945 Loarte, A., et al., Nucl. Fusion 38 (1998) 331 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

40 ELM Particle Losses (IIa) Divertor ELM Particle Flux Consistent Ballooning Origin of ELM MHD crash Mirnov Coil (a.u.) Midplane D α (a.u.) Inner Divertor D α (a.u.) Outer Divertor D α (a.u.) Similar Observations in several Divertor Tokamaks common ELM Origin & II B Particle ELM Outer I sat (a.u.) Inner Divertor D α (a.u.) Inner I sat (a.u.) Time (µs) Mirnov Coil (a.u.) -2-3 Midplane D α (a.u.) Outer Divertor D α (a.u.) 0.5 Outer I sat (a.u.) Inner I sat (a.u.) Time (µs) JG c JG c τ II = 150 µs τ II = 200 µs τ in out Dα (µs) JET. Loarte + JT 60U. Chankin + ASDEX Upgrade. Horton + DIII D. Porter JET JT 60U ASDEX Upgrade DIII D τ II Front (µs) Loarte, A., et al., Plasma Phys. Contr. Fus. (2002), Loarte, A., et al., 15 th PSI Conference, Gifu 2002 Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

41 P X ray (W/m 2 ) ELM Divertor Power Fluxes (Ia) From Electron Bremsstrahlung ~ q e can be estimated R Bremsstrahlung (C) ~ /2 kt e /m e c 2 (More precise Estimate f e div (x,t)) T e,ped = 1.4 kev lower T e,ped lower W ELM div,electron τ e ELM ~ constant but τ IR ELM ~ 1/T e,ped 5000 Maximum Electron Power Flux 150 P_X ray T e,ped = 1.0 kev P_e Pelectron (MW/m2 ) Sheath vs. Core W ELM (MJ) B impedance to Energy Loss? Gill, R., et al., Nucl. Fusion 38 (1998) 1461, Loarte, A., et al., 43 rd APS Conf & Plasma Phys.Contr.Fus.(2002) Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching

42 Divertor Asymmetries (IIa) Divertor Design + Fuelling used to affect In/Out Divertor Asymmetry JET Mk II Gas Box Maggi, C. et al., 26 th EPS Conference, Maastricht, 1999 Kukushkin, A., et al., Nucl. Fusion 39 (2002) 187 Insulating Inner Outer Divertor Neutral Flow allows Detachment Control but No Insulation produces most Symmetric In/Out Divertor Plasmas ITER Divertor designed with large Inner Outer Neutral Conductance Alberto Loarte New Trends in Plasma Physics II Max-Planck-Institut für Plasmaphysik - Garching