Association EuratomCea Edge Localised Modes Physics and Edge

Association Euratom-Cea Edge Localised Modes Physics and Edge Issues in Tokamaks. presented by Becoulet M. G. Huysmans (1), Y. Sarazin (1), X. Garbet(1), Ph. Ghendrih (1), F. Rimini (1), E. Joffrin (1), Litaudon X. (1), P. Monier. Garbet (1) , J. -M. Ané (1), P. Thomas (1), A. Grosman (1), (1) Association Euratom-CEA, CE Cadarache, F-13108 St. Paul-lez-Durance, France. V. Parail (2), H. Wilson (2), P. Lomas (2), P. de. Vries(2) , K. -D. Zastrow(2), G. F. Matthews (2), J. Lonnroth (2), S. Gerasimov(2), S. Sharapov(2), M. Gryaznevich(2), G. Counsell(2), S. Fielding(2), A. Kirk(2), M. Valovic(2), R. Buttery(2) , (2) Euratom/UKAEA Association, Fusion Culham Science Centre, Abingdon, OX 14 3 EA, UK. G. Saibene (3), R. Sartori (3), A. Loarte (3) ; (3) EFDA Close Support Unit (Garching), 2 Boltzmannstrasse, Garching, DE. A. Leonard (4), P. Snyder (4), L. L. Lao(4), P. Gohil(4), T. E. Evans(4), (4) General Atomics, 3550 General Atomics Court, P. O. Box 85608 San Diego, CA, U. S. A. Y Kamada (5), A Chankin (5), N. Oyama(5), T. Hatae(5) , N. Asakura(5), (5) Japan Atomic Energy Research Institute (JAERI), Japan O. Tudisco (6), E. Giovannozzi(6) , F. Crisanti(6), (6) Associazione EURATOM-ENEA sulla Fusione, C. R. Frascati, Frascati , Italy C. P. Perez (7), H. R. Koslowski(7) , (7) Institut für Plasmaphysik, Forschungszentrum Julich, Germany (8) T. Eich , A. Sips(8), L. Horton(8) , P. Lang (8), A. Hermann (8), J. Stober(8), W. Suttrop(8), (8) Association Euratom-IPP, MPI fur Plasmaphysik, 2 Boltzmannstrasse, Garching, D-85748, Germany P. Beyer(9), (9) UMR 6633 PIIM CNRS-Université de Provence, F-13397 Marseille Cedex 20, France. S. Saarelma(10), (10) Helsinki University of Technology, Euratom-TEKES Association, FIN-02015 HUT, Finland R. A. Moyer (11) University of California, San Diego, La Jolla CA 92093, U. S. A. and contributors to JET-EFDA Workprogramme. th th 1/32 30 St. Petersburg, July 2003 M. 30 EPS, Petersburg, 7 -11 July, 2003 M. Bécoulet

Outline. 1. Introduction. -High confinement scenarios for ITER and ELMs. 2. H-mode scenarios and ELMs (theory + experiment). -Ballooning-peeling linear MHD model. -Pedestal and SOL transport, non-linear models. -ELM size: role of density, triangularity, high q 95, high bp. -High confinement regimes with Type II ELMs for ITER? 3. Internal Transport Barrier (ITB) scenario and ELMs. -Combined ITB+ ETB scenarios. 4. Active control of ELMs. -Edge ergodisation, edge current, pellets. th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 2/32

ELM cycle: periodic loss of confinement ELM = plasma edge MHD instabilities typical for H-modes in tokamaks => periodic fast (200 ms) relaxations of edge pressure => energy to SOL =>divertor+wall. DIII-D: - A. Leonard PPCF 2002 JET: G. Saibene PPCF 2002 JET: Ph. Ghendrih JNM (2003) Dne=> convective before D after Wdia Te ped DTe=> conductive before ne ped after radius(m) th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 time(s) M. M. Bécoulet divertor 3/32

Experimental scaling for ELMs types e: Ty pe I JET: Sartori R. PPCF 2003 submitted -m od p y T I I e H II I e p y T : e d o m - H Type I : low f. ELM, high Pped=> high confinement, but large energy losses per ELM. Type II : regimes in highly shaped plasmas, high Pped, (confinement ~like Type I ELMs), small edge MHD activity, but for narrow operational window. e d L-mode mo L Type III: (at low power or at high density): higher f. ELM, small energy losses per ELM, but lower Pped=> low confinement. L/H threshold ~0. 45 ne 0. 75 BTR 2 (MW) th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 4/32

ELMs are problematic for ITER reference scenarios Q=Pfusion/Padd. ~10(Aymar et al 2001) : high confinement (H 98 y>1); high density (>0. 8 n. GR), high d=0. 5 and th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 heat flux to SOL ITB pressure pedestal pressure (=confinement) is limited by MHD radius heat flux to SOL core ITB scenario ETB pressure H-mode scenario (or advanced regimes w/o ITB? ) ETB acceptable (material limits=melting, erosion, evaporation…=>reasonable divertor life-time) heat loads on the divertor target plates: DWELMped<510 MJ (if 60% goes to the divertor S~3 m 2 )(Federici PSI 2002). ITB erosion by large ELMs radius M. M. Bécoulet 5/32

Experiment evidence from many tokamaks: ballooning structure -Ballooning structure of ELMs=> collapse of Te, ne on the LFS. -Parallel SOL transport => divertor (~50% : T. Eich EPS 2001 ); -SOL perpendicular turbulent transport (“tails”, “blobs”) => wall MAST: G. Counsell 2002 MAST: A. Kirk 2003 Te, ne collapse on LFS wall Outboard D before during after SOL plasma edge inboard outboard th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 6/32

Linear ideal MHD theory: ELMs=ballooning-peeling modes. Linear MHD stability analysis (codes MISHKA, GATO, ELITE). -Ballooning modes driven by pressure gradient => pedestal, outboard (=LFS), high n. -Peeling (kink) driven by edge current (+bootstrap) =>X-point, low n=1 -4 -Coupled peeling-ballooning => LFS, pedestal, n~10 -20 (JET). JET(MISHKA): G. Huysmans 9 th. EFPW 2001 jedge 0. 8 th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet Peeling component ballooning-peeling: n=12 Pedestal shoulder JET: M. Becoulet et al PPCF 2002 1 7/32

Pressure collapse in ELM: non-linear modelling MISHKA: modes structure, growth rate, ~ egt : g 2~n( - crit) if > crit ; d. Br (ergodisation)+d. V(convection) TELM (a) : M. Becoulet, G. Huysmans et al 2003 n diffusio telm~200 ms 0. 0. 2 0. 4 before 0. 6 time (s) after th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet Losses in the SOL: Sloss= - P/t// ELM 8/32

Turbulence modelling: ELMs? Resistive ballooning turbulence (d. B=0, d. F=0 ) modelling : periodic energy bursts through ETB. Estimations for “ELM” time ~250 ms! More development needed both with MHD + turbulence (DIII-D, BOUT-X. Xu et al New J. of Phys. 2002) (P. Beyer , to be submitted Po. P 2003) core SOL th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 9/32

Particle transport in SOL to the inner and outer divertor. ELM collapse on the LFS => inner/outer delay in D : Dt delay~ t// (ions) =2 p. Rq 95/Cs, ped. Increases with the density. JET : A. Loarte et al PPCF 2002 JT-60 U: A. Chankin, N. Oyama et al NF 2002, PPCF 2001 d. Bq/dt ELM collapse inner outer Inner HFS Outer LFS HFS LFS th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 10/32

Type I ELM time: tdiv. ELM > ~ t. MHDELM ~ 150 -300 ms (JET), similar in JT-60 U, DIII-D, AUG~1 ms. Not identified parametric dependence. Weak? Energy into divertor is deposited with ion flux time t//ion => tdiv. ELM increases with the density. JET: A. Loarte PPCF 2002 IR data th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 11/32

Toroidal “rotation” of ELM Toroidal asymmetry of Type I ELM in JET (similar TCV: H. Reimerdes NF 1998). Propagation in electron diamagnetic direction: ~t. SOL//. Not explained by linear MHD. JET(M. Becoulet, G. Saibene 2003) toroidal Mirnov coils Broken coils Low nped F=3° High nped th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 12/32

ELM “size” decreases with the density. What are the key factors to decrease ELM size keeping high confinement? Multi-machine experimental scaling: DWELM/Wped decreases with ne, ped (n*ped, , t. Front// … ). A. Loarte PPCF 2002 What physics? ne => Te -MHD=>botstrap current -Pedestal transport? -SOL transport? t// =2 p. Rq 95/Cs, ped Not identified yet Log scale th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 13/32

Edge bootstrap current decreases with density. MISHKA modelling for JET: diffusion of edge bootstrap current improves stability for low n peeling modes. Main difficulty: sensitivity of stability diagram to small changes in Te, ne, Jz profiles, no direct measurements of edge current. sta un ble sta ble JET(MISHKA): G. Huysmans 9 th. EFPW 2001 th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 14/32

ELM size =ELM affected area? Open question. As density increases pedestal width (less obvious on JET!), bootstrap current , mainly conductive losses DT/T with density Modelling => Radial width of mode decreases =>Smaller ELMs? DIII-D (ELITE: P. Snyder et al IAEA 2002) DIII-D (A. Leonard et al, PPCF-2002) th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 15/32

Transport modelling(TELM): smaller affected area = smaller ELMs? TELM ( M. Becoulet et al 2003) Large ELM area : DWELM/Wped~3% th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 Narrow ELM area: DWELM/Wped~1. 2% M. M. Bécoulet 16/32

ELM size: role of plasma shaping=> improved MHD stability High triangularity (d) => higher pedestal pressure => higher confinement (AUG, JT-60 U, DIII-D, JET…) JET: G. Saibene et al PPCF 2002 JET(MISHKA): G. Huysmans 9 th EFPW 2001 Low d High d H 98 y ITER Pressure gradient Ballooning unstable kink unstable Edge current ne/n. GR(%) Similar results for AUG, JT-60 U, DIII-D… th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 17/32

High triangularity (edge magnetic shear)=>“Grassy” ELMs in JT-60 U High confinement regimes with small “grassy” ELMs recipe => high magnetic shear: d>0. 5 -0. 6, high q 95=3. 5 - 6, high bp~2. JT-60 U Y. Kamada et al PPCF 2002 th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 high bp(~2 ) helps =>grassy” at q 95=3. 6 (in ITER~3) M. M. Bécoulet 18/32

Type II ELMs in ASDEX-Upgrade. AUG: A. Sips 9 th. EFPW 2001 To Double Null th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 Type II ELMs : d=0. 4 (Double Null is important!), q 95>4. 2, n/n. GR~0. 85 -0. 95(high density) , H 98~1. Broadband MHD: n=3, <30 k. Hz. Low heat load into divertor. Advanced scenario with Type II at high bp. (0. 8 MA/1. 7 T, 10 MW NBI) d=0. 4 (Double Null configuration) q 95=3 (q 0~1 to avoid saw-teeth) n/n. GR~0. 88, H 98 -P~1. 2 -1. 3, bp=1. 8, b. N=3. 5 Effect of high bp? -Core confinement is improved (turbulence; bootstrap =>flat shear…) -ELMs Type II at lower q 95 ~3. 19/32 M. Bécoulet

Linear ideal MHD (GATO): ELM area is small for Type II ELMs ELM affected area decreases at high q 95 +high d for the same pressure profile. Double Null configuration increases edge shear even more. GATO (for AUG) S. Saarelma et al, NF(2003) n=3 th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 20/32

JET: mixed Type I+Type II d~0. 5; q 95=3. 4, n/n. GR~0. 9 -1. 1, H 97~1. High density (n*~0. 6 -0. 8!) => smaller Type I + Type II = broad band MHD <30 k. Hz, n=8 (Washbroad resistive modes? Ch. Perez NF 2003). SN and DN configurations were tried. Not enough factors JET to suppress Type I ELMs on JET? And for ITER? Other regimes w/o ELMs QH (DIII-D), EDA(C-mod)… JET: G. Saibene et al PPCF(2002), see EPS 2003 ne=0. 8 n. GR Da Da ne=1. 1 n. GR Wdia ne ne th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 21/32

Conclusions (I): ELMs in H-modes -Ideal MHD + transport models describe many experimental observations: ballooning structure, fast relaxation of Pped, MHD ELM time: t. ELM, frequency: f. ELM. - Type I ELM MHD time (= typical pedestal crash time) is found ~150 -300 ms for many machines. Parametric dependence is not identified yet. -ELM rise time on divertor target is correlated with ion // SOL transport. - Key factors to decrease ELM size? -high pedestal density(collisionalty? ); -high d, high q 95, high bp; -Regimes with benign Type II ELMs at high d demonstrated ITER– like H 97~1, n/n. GR~0. 8 -0. 9, but not for ITER-like parameters (n*~0. 05, bp~1, q 95~3)=> Low n*, high power, high current… th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 22/32

Double barriers: ETB+ITB: high bp with “grassy” ELMs. High bp~2, high q 95~6. 9, high d~0. 5 => ITB+ETB with grassy ELMs => high performance (HHy 2~1. 2, n/n. GR~0. 6) + divertor heat load is reduced by factor 4 -5 as compared to Type I ELMs. JT-60 U: Y. Kamada PPCF(2002) th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 23/32

QDB Quiescent Double Barrier =ITB+QH-mode without Type I ELMs on DIII-D (b. N=3. 5, wide range of q 95, d). But : counter NBI injection, nped~0. 1 n. GR. Interesting from the point of view: low n* pedestal. D-III-D: P. Gohil 8 th IAEA TCM 2001 th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 24/32

ITB+Type I ELMs ? Type III ELMs? Usually Type I ELMs are not compatible with large (r ITB> 0. 5) ITBs in JET, DIII-D: ITB erosion by Type I ELMs. If no pure Type II regimes => small Type III ELMs +ITB (=improved core confinement to compensate poor edge confinement). But how to keep Type III edge? Type I JET: M. Becoulet PPCF(2002) Type III wall Te (ECE) plasma centre th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 25/32

Perturbation from Type I ELM propagates to ITB region? Suggestion from theory: perturbation from ELM propagates inside => fast avalanche-like transport after an ELM: inward –outward turbulent fluxes. Why ITB is affected? Slow (t confinement) erosion of ITB, not MHD collapse! Rotation shear is affected ? Mechanism is unknown. JET: Y. Sarazin PPCF(2002) ITB pressure before 1 st ELM before 2 nd ELM Steeper gradient => unstable centre th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet SOL 26/32

High triangularity ITB on JET. Main difficulty for ITB scenario at high d~0. 5 is Type I ELMs avoidance. JET 2003: ITBs (3. 4 T/1. 5 MA) with Type III edge with D 2: n/n. GR~0. 7, H 98 y~1. 3, b. N~1. 8, bp~1. 5 , q 95~7, lasts~ 6 s. JET: M. Becoulet , P. Lomas, O. Tudisco, F. Rimini, K. -D. Zastrow et al th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 27/32

High triangularity=>higher density Higher density: 0. 7 n. GR at HT(d~0. 5) compared to 0. 4 n. GR LT(d~0. 2), but H 89 = 2 (at LT)=>1. 7(at HT). Future => larger ITB : r ITB>0. 5=> performance, higher bp, lower q 95. JET: M. Becoulet et al (2003) JET: F. Rimini et al(2003) High d ITBs th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 28/32

Conclusions(II): ELMs in ITBs -Combined regimes with ITB and ETB: ITB with “grassy” ELMs at high triangularity, high q 95, high bp were demonstrated in JT-60 U. ITB+ETB w/o ELMs : QDB in DIII-D (but counter NBI, low n/n. GR~0. 1) -High triangularity ITBs (d~0. 5, n/n. GR~0. 7, H 98 y~1. 3, b. N~1. 8, bp~1. 5, q 95~7 ) with Type III ELMs were demonstrated on JET. Active control of ELMs: -gas puffing; -impurity (increased Prad=> control Te, ped, but impurity accumulation? ) -edge current (Ip ramp-up, -down experiments => support peeling-ballooning picture of ELMs, but very Pped, d. Ip/dt dependent, large tres ITER) -edge ergodisation, -pellets… th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 29/32

ELMs control by d. Brexternal? External control coils d. Br(t) => edge ergodisation: < crit, or artificial ELMs. Compatibility with high confinement regimes? COMPASS-D: S. Fielding et al EPS 2001 TCV: A. Degeling et al 2003 d. Br=0 R. Moyer, T. Evans : DIII-D (C-coils) EPS 2002 See G. Jackson , EPS 2003 Friday -P-4. 47 d. Br=0 More planned in 2003 Max d. Br th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 30/32

Pellets => increase of n*, artificial ELMs are similar to natural. ASDEX-Upgrade: P. Lang (EPS 2002) see also this conference With pellets: 20 Hz smaller Type I ELMs W/o pellets: ~ 3 Hz large compound ELMs th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 31/32

Conclusions (towards ITER integrated scenario) 1. Key factors to decrease Type I ELM size: -high d, high q 95, high bp=> Type II ELMs for ITER? -increase pedestal density (n*, t//ion, . . ? ) => understanding of SOL energy and particles transport during an ELM is missing for the definitive predictions for ITER. 2. H-modes and combined advanced scenarios (with and w/o ITBs) at high triangularity high density with small ELMs demonstrated ITER – like performance (H 97 y>1, n/n. GR~0. 7 -0. 9) , but for the moment not for ITER-like parameters : n*~0. 05, bp~1, q 95~3 (H-mode); q 95~4 -5(ITBscenario). Aim: high current, high power, low pedestal collisionality regimes! 3. Active control of ELMs is progressing => should demonstrate the compatibility with high confinement regimes for ITER. th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 32/32

Transport through ETB increases with density=>smaller ELMs increases with density => if < crit. , no ELMs! , (first demonstrated with JETTO: V. Parail EPS 2001). But in experiment Type I=> Type III transition with ne increase, low confinement. TELM: M. Becoulet et al 2003 before after th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 33/32

ITB+Type I ELMs ? Type III ELMs? Usually Type I ELMs are not compatible with large (r ITB> 0. 5) ITBs in JET, DIII-D: ITB erosion by Type I ELMs. If no pure Type II regimes => small Type III+ITB(improved core confinement) ? JET: M. Becoulet PPCF(2002) Type III wall Type I JET: R. Sartori +M. Becoulet PPCF 2002 ITBs Te (ECE) s ard d n Sta I e Typ plasma centre e d o H-m II e. I p y T L-mode th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 34/32

Edge current: Ip ramps, drive? Ip ramp-up 55601 55599 Ip ramp-down larger Type I ELMs! dithering Type I nped(55601, 55599) Edge current (Ip ramp-up): 1)first improve stability; 2)then destabilise peeling modes: (when kink unstable): Type III or dithering L-mode. The result is very sensitive to edge Te, ne, d. Ip/dt… tres for ITER? ng i n=14 -22 n o o le l l b Ba sta un Ip ramp-up Ip ramp-down ink nk e w bl o L sta un Pressure gradient JET: Becoulet M. et al 2003 Tped current (similar results MAST : Gryasnevich M. et al 2002; COMPASS-D, S. Fielding EPS 2001 ) th th 30 St. Petersburg, July 2003 30 EPS, Petersburg, 7 -11 July, 2003 M. M. Bécoulet 35/32