30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 1/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet 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 St. Paul-lez-Durance, France. V.Parail (2), H. Wilson (2), P. Lomas (2), P. deVries (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, OX14 3EA, 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 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 T.Eich (8), 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 6633PIIM CNRS-Université de Provence,F Marseille Cedex 20, France. S. Saarelma (10), (10) Helsinki University of Technology, Euratom-TEKES Association, FIN HUT, Finland R.A. Moyer (11) (11) University of California, San Diego, La Jolla CA 92093,U.S.A. and contributors to JET-EFDA Workprogramme. Association Euratom-Cea

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 2/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet 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  p. -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. Outline.

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 3/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet ELM = plasma edge MHD instabilities typical for H-modes in tokamaks => periodic fast (200  s) relaxations of edge pressure => energy to SOL =>divertor+wall. DD Wdia Te ped ne ped JET: Ph.Ghendrih JNM (2003) divertor JET: G. Saibene PPCF2002 ELM cycle: periodic loss of confinement time(s) after before DIII-D:- A. Leonard PPCF2002  ne=> convective  Te=> conductive radius(m)

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 4/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Type I : low f ELM, high P ped => high confinement,but large energy losses per ELM. Type II : regimes in highly shaped plasmas, high P ped, (confinement ~like Type I ELMs), small edge MHD activity, but for narrow operational window. Type III: (at low power or at high density): higher f ELM, small energy losses per ELM, but lower P ped => low confinement. Experimental scaling for ELMs types L-mode H-mode:Type III Type II JET: Sartori R. PPCF2003 submitted H-mode:Type I L-mode L/H threshold ~0.45n e 0.75 B T R 2 (MW)

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 5/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet ITER reference scenarios Q=P fusion /P add. ~10 (Aymar et al 2001) : high confinement (H98 y >1); high density (>0.8n GR ), high  and acceptable (material limits=melting, erosion,evaporation…=>reasonable divertor life-time) heat loads on the divertor target plates:  W ELM ped <5- 10MJ (if 60% goes to the divertor S~3m 2 ) (Federici PSI 2002). ELMs are problematic for ITER. pressure radius ETB core pedestal pressure (=confinement) is limited by MHD H-mode scenario (or advanced regimes w/o ITB?) heat flux to SOL radius ITB ITB scenario ITB erosion by large ELMs pressure heat flux to SOL ETB ITB

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 6/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet plasma Experiment evidence from many tokamaks: ballooning structure MAST: G.Counsell 2002 Te, ne collapse on LFS -Ballooning structure of ELMs=> collapse of Te, ne on the LFS. -Parallel SOL transport => divertor (~50% : T.Eich EPS2001 ); -SOL perpendicular turbulent transport (“tails”, “blobs”) => wall Outboard D  MAST: A. Kirk 2003 wall plasma edge inboard outboard before during after SOL

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 7/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet 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: M. Becoulet et al PPCF2002  j edge  ballooning-peeling: n=12  JET(MISHKA): G.Huysmans 9thEFPW Pedestal shoulder Peeling component

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 8/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet MISHKA: modes structure, growth rate, ~ e  t    n  crit  if  crit ;  TELM (  ) : M. Becoulet,G. Huysmans et al 2003 Losses in the SOL: S loss = - P/  // before after Pressure collapse in ELM: non-linear modelling  B r (ergodisation)+  V(convection) time (s)  elm~200  s diffusion ELM

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 9/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Resistive ballooning turbulence (  B=0,  =0 ) modelling : periodic energy bursts through ETB. Estimations for “ELM” time ~250  s! More development needed both with MHD + turbulence (DIII-D, BOUT-X.Xu et al New J. of Phys. 2002) (P.Beyer,to be submitted PoP2003 ) Turbulence modelling: ELMs? SOL core

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 10/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet ELM collapse on the LFS => inner/outer delay in D   t delay ~  // (ions) =2  Rq 95 /C s, ped. Increases with the density. JET : A. Loarte et al PPCF2002 Particle transport in SOL to the inner and outer divertor. Outer LFS Inner HFS ELM collapse inner outer LFS HFS JT-60U: A.Chankin, N. Oyama et al NF2002, PPCF 2001 dB  /dt

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 11/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Type I ELM time:  div ELM > ~  MHD ELM  MHD ELM ~  s (JET), similar in JT-60U, DIII-D, AUG~1ms. Not identified parametric dependence. Weak? IR data Energy into divertor is deposited with ion flux time  // ion =>  div ELM increases with the density. JET: A.Loarte PPCF2002

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 12/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Toroidal asymmetry of Type I ELM in JET (similar TCV: H. Reimerdes NF1998). Propagation in electron diamagnetic direction: ~  SOL //. Not explained by linear MHD. toroidal Mirnov coils Toroidal “rotation” of ELM JET (M.Becoulet, G. Saibene 2003) Broken coils Low n ped High n ped 

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 13/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet What physics? n e => T e ELM “size” decreases with the density. What are the key factors to decrease ELM size keeping high confinement? Multi-machine experimental scaling:  W ELM /W ped decreases with with n e, ped ( * ped,,  Front // … ). -SOL transport? -Pedestal transport? A. Loarte PPCF MHD=>bootstrap current  // =2  Rq 95 /C s, ped Not identified yet Log scale

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 14/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet 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 T e, n e, J z profiles, no direct measurements of edge current. JET(MISHKA): G.Huysmans 9thEFPW 2001 Edge bootstrap current decreases with density. unstable stable

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

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 16/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Transport modelling(TELM): smaller affected area = smaller ELMs? TELM ( M. Becoulet et al 2003) Large ELM area :  W ELM /W ped ~3% Narrow ELM area:  W ELM /W ped ~1.2%

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 17/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet H98y n e /n GR (%) High triangularity (  => higher pedestal pressure => higher confinement (AUG, JT-60U, DIII-D, JET…) JET(MISHKA): G.Huysmans 9 th EFPW 2001 JET: G. Saibene et al PPCF2002 Edge current Pressure gradient Low  High  ELM size: role of plasma shaping=> improved MHD stability ITER stable Similar results for AUG,JT-60U, DIII-D… kink unstable Ballooning unstable

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 18/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet High confinement regimes with small “grassy” ELMs recipe => high magnetic shear: , high q 95 =3.5- 6, high  p ~2. high  p (~2 ) helps =>grassy” at q 95 =3.6 (in ITER~3) JT-60U Y. Kamada et al PPCF2002 High triangularity (edge magnetic shear)=>“Grassy” ELMs in JT-60U

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 19/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Type II ELMs in ASDEX-Upgrade. Type II ELMs :  =0.4 (Double Null is important!), q 95 >4.2, n/n GR ~ (high density), H 98 ~1. Broadband MHD: n=3,<30kHz. Low heat load into divertor. Advanced scenario with Type II at high  p. (0.8MA/1.7T, 10MW NBI)  =0.4 (Double Null configuration) q 95 =3 (q 0 ~1 to avoid saw-teeth) n/n GR ~0.88, H 98-P ~ ,  p =1.8,  N =3.5 Effect of high  p ? -Core confinement is improved (turbulence; bootstrap =>flat shear…) -ELMs Type II at lower q 95 ~3. AUG: A. Sips 9thEFPW 2001 To Double Null

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

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 21/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet  ; q 95 =3.4, n/n GR ~ , H97~1. High density ( *~ !) => smaller Type I + Type II = broad band MHD <30kHz, n=8 (Washbroad resistive modes? Ch.Perez NF2003). 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 n e =0.8n G R n e =1.1n GR JET: mixed Type I+Type II DD DD Wdia ne Wdia

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 22/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet -Ideal MHD + transport models describe many experimental observations: ballooning structure, fast relaxation of P ped, MHD ELM time:  ELM, frequency: f ELM. - Type I ELM MHD time (= typical pedestal crash time) is found ~  s 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 , high q 95, high  p; -Regimes with benign Type II ELMs at high  demonstrated ITER– like H97~1, n/nGR~ , but not for ITER-like parameters ( *~0.05,  p ~1, q 95 ~3)=> Low *, high power, high current… Conclusions (I): ELMs in H-modes

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 23/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Double barriers: ETB+ITB: high  p with “grassy” ELMs. High  p~2, high q 95 ~6.9, high  => ITB+ETB with grassy ELMs => high performance (HHy2~1.2, n/n GR ~0.6) + divertor heat load is reduced by factor 4-5 as compared to Type I ELMs. JT-60U: Y. Kamada PPCF(2002)

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 24/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet D-III-D: P. Gohil 8 th IAEA TCM2001 Quiescent Double Barrier =ITB+QH-mode without Type I ELMs on DIII-D (b N =3.5, wide range of q 95,  ). But : counter NBI injection, n ped ~0.1n GR. Interesting from the point of view: low * pedestal. QDB

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 25/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Usually Type I ELMs are not compatible with large (  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? JET: M. Becoulet PPCF(2002) Type III Type I ITB+Type I ELMs ? Type III ELMs? Te (ECE) wall plasma centre

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

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 27/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Main difficulty for ITB scenario at high  ~0.5 is Type I ELMs avoidance. JET 2003: ITBs (3.4T/1.5MA) with Type III edge with D 2 : n/n GR ~0.7, H 98y ~1.3, b N ~1.8,  p ~1.5, q 95 ~7, lasts~ 6s. JET: M. Becoulet, P. Lomas, O. Tudisco, F. Rimini, K.-D. Zastrow et al High triangularity ITB on JET.

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 28/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet JET: M. Becoulet et al (2003) JET: F.Rimini et al(2003) Higher density  0.7 n GR at HT(  compared to 0.4n GR LT(  but H89 = 2 (at LT)=>1.7(at HT). Future => larger ITB :  ITB >0.5=> performance, higher  p, lower q 95. High triangularity=>higher density High  ITBs

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 29/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet -Combined regimes with ITB and ETB: ITB with “grassy” ELMs at high triangularity, high q 95, high  p were demonstrated in JT-60U. ITB+ETB w/o ELMs : QDB in DIII-D (but counter NBI, low n/n GR ~0.1) -High triangularity ITBs (  ~0.5, n/n GR ~0.7, H 98y ~1.3, b N ~1.8, b p ~1.5, q 95 ~7 ) with Type III ELMs were demonstrated on JET. Conclusions(II): ELMs in ITBs Active control of ELMs: -gas puffing; -impurity (increased P rad => control T e, ped, but impurity accumulation?) -edge current (Ip ramp-up, -down experiments => support peeling-ballooning picture of ELMs, but very P ped, dI p /dt dependent, large  res ITER ) -edge ergodisation, -pellets…

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 30/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet External control coils  B r (t) => edge ergodisation:  <  crit, or artificial ELMs. Compatibility with high confinement regimes? COMPASS-D: S. Fielding et al EPS2001 TCV: A. Degeling et al 2003 R. Moyer,T. Evans : DIII-D (C-coils) EPS2002  Br  Max  Br ELMs control by  B r external ? More planned in 2003 See G. Jackson, EPS 2003 Friday -P-4.47

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 31/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Pellets=> increase of *, artificial ELMs are similar to natural. Pellets. ASDEX-Upgrade: P. Lang (EPS2002) see also this conference W/o pellets: ~ 3Hz large compound ELMs With pellets: 20 Hz smaller Type I ELMs

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 32/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet (towards ITER integrated scenario) 1. Key factors to decrease Type I ELM size: -high , high q 95, high  p => Type II ELMs for ITER? -increase pedestal density ( *,  // 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 97y >1, n/n GR ~ ), but for the moment not for ITER-like parameters : *~0.05,  p ~1, q 95 ~3 (H- mode); q 95 ~4-5(ITB-scenario). 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. Conclusions

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 33/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet increases with density => if  Type III transition with n e increase, low confinement. TELM: M. Becoulet et al 2003 before after Transport through ETB increases with density=>smaller ELMs

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 34/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Usually Type I ELMs are not compatible with large (  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 Type I ITB+Type I ELMs ? Type III ELMs? Te (ECE) wall plasma centre JET: R.Sartori +M. Becoulet PPCF 2002 ITBs Type III Standard H-modes Type I L-mode

30 th EPS, St. Petersburg, 7-11 July, 2003M. Bécoulet 35/32 30 th EPS, St. Petersburg, July 2003 M. Bécoulet Tped nped(55601,55599) JET: Becoulet M. et al 2003 dithering larger Type I ELMs! Type I Edge current (I p 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 T e, n e, dI p /dt…  res for ITER? Ip ramp-up Ip ramp-down current Ballooning unstable Pressure gradient Ip ramp-up Ip ramp-down Low n kink unstable n=14-22 (similar results MAST : Gryasnevich M. et al 2002; COMPASS-D, S. Fielding EPS2001 ) Edge current: Ip ramps, drive?