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Overview of JET results

Overview of JET results. New on JET for 2006/2007 Divertor for highly shaped (high d ) plasmas, upgraded power and enhanced diagnostic capability. M. L. Watkins on behalf of JET-EFDA contributors 21 st IAEA Fusion Energy Conference, Chengdu, China 16 October 2006. Steady. State scenario.

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Overview of JET results

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  1. Overview of JET results New on JET for 2006/2007Divertor for highly shaped (high d) plasmas, upgraded power and enhanced diagnostic capability M. L. Watkins on behalf of JET-EFDA contributors21st IAEA Fusion Energy Conference, Chengdu, China 16 October 2006

  2. Steady State scenario Hybrid scenario #58179 #57971 q(R) q(R) ~ t ~ t 4.6s 4.2s q 2 1< q <1.5 min min shear reversal Major radius [m] Major radius [m] ITER Baseline, Hybrid and ITB scenarios Schematic of tokamak plasma profiles for various operating scenarios Content of talk • q profile control of MHD and transport Pressure, temperature or density • Core MHD and fast particles • Density peaking and impurity control • ELMs and ELM control • Material erosion, migration and deposition • Summary and conclusions Normalised radius r/a Pa/Ploss ~ n tET f(Zeff)~ b tEB2g(Zeff) Performance improvement by MHD, confinement and impurity control

  3. Pulse No: 67940 1.8MA/1.7T Ip (MA) PNBI (MW) PLH (MW) 4xli bN qo (MSE) n/nG No sawteeth Ha Time (s) Hybrid modes at low q95~3 reach bN~3 Courtesy of E. Joffrin (2006) Hybrid and H-mode in ITER-like shape Characteristics of hybrid discharge at q95= 3.2 q95~3 Hybrid 2006 H89bN/q952 Maintain q0>1 to avoid sawteeth q95~4 Figure of merit Hybrid 2003 H-mode 2006 Bootstrap current ~ e.bp • Hybrid performance similar to H-mode at high q95~4 • Improved hybrid performance at low q95~3, slightly better than H-mode withb controlled in real time

  4. Internal Transport Barriers with q95~5 and 32MW X. LITAUDON (EX/P1-12) TUES am Pulse characteristics 1.9MA/3.1T Temperature and density profiles 1.9MA/3.1T During ITB Before ITB r/a Time (s) 2006 ITB discharges extended to lower q95~5, higher power (32MW)and high core and edge densities

  5. Control of core MHD (sawteeth) demonstrated J. ONGENA (EX/P6-9) FRI am Sawteeth can destabilise Neoclassical Tearing Modes and degrade performance Fast particle stabilised sawteeth destabilised with ICCD Calculated magnetic shear t=23s Pulse No: 58934 Pulse No: 58934 Te0(keV) Magnetic shear PRF(MW) Time (s) • Large sawteeth created by ICRF accelerated fast particles • Sawteeth destabilised subsequently, with the application of ICCD F. PORCELLI(EX/7-4RA)FRI am r/a • Internal kink mode destabilisation requires critical shear of 0.2 for this discharge • Critical shear exceeded near q=1 with -900 ICCD phasing (counter-current), explaining observed sawtooth destabilisation Criterion for sawtooth crash Sq=1 > Sq=1 critical Increase shear near q=1 dW / (Sq=1tA) < w*I / 2

  6. Observation of fast particle losses from core MHD (sawteeth and tornado modes) Energy & pitch angle of lost fast particles from scintillator probe Spectrograms showing tornado modes Sawteeth & tornado modes appear with q0<1 67673 1.8MA/2.7T Interferometer (core channel) 245 240 235 230 225 220 Frequency (kHz) X-mode refl. Magnetics 245 240 235 230 225 Between sawteeth During sawtooth crash • Multichannel interferometer (and X-mode reflectometer) enable mode localisation 220 16.8 17.0 17.2 17.4 • Fast particle losses (p, T, D) during tornado phase different signature to those during sawtooth crash • Sawteeth losses characteristic of ICRH-accelerated ions (p, D) Time (s) • Core interferometer channel shows tornado modes before sawtooth crash • Modes not seen on edge channel, confirming core localisation A. MURARI (IT/P1-23) TUES am

  7. Significant density peaking expected on ITER H. WEISEN (EX/8-4) FRI pm Merged JET-AUG database on density peaking in ITER Baseline ELMy H-modes • Multi-machine data confirm collisionality,eff, as most relevant parameter for density peaking • Increasing peaking with decreasing eff • Peaking requires anomalous particle pinch, in addition to neutral sources n0/<n>vol • Scaling of density peaking to ITER with effas regression variable  • ne0/<ne> > 1.35 eff • Favourable for fusion output, bootstrap current fraction, density limit New ITER-like ICRH antenna on JET (installation April 2007) will allow database to be extended to higher power, neutral source free RF heated plasmas Could impact on impurity accumulation

  8. Impurity density peaking less than neoclassical He, Ne, Ar Ni (LA) Soft X-rays (a.u.) 17 18 19 Time (s) Measured and predicted density peaking at r/a=0.55 C. GIROUD (EX/8-3) FRI pm • Neoclassical theory predicts strong impurity peaking • Transient behaviour of injected and laser ablated impurities shows impurity peaking less than neoclassical Pulse No:66134 Neoclassical Measurement -RVz/Dz GS2 w/o Thermodiffusion -RVz/Dz Gz= -Dznz + nzVz R/LNz=RVz/Dz GS2 • Impurity transport at ITER-like collisionality found to be anomalous • Turbulence theory predicts saturation in peaking as a function of Z at high Z (consistent with measurements) • At low Z prediction of low peaking with thermodiffusion, high peaking without Central peaking (r/a=0.15), albeit less than neoclassical, can still persist

  9. Core impurity peaking can be controlled with electron ICRF heating Effect of Minority (ion) heating (MH) and Mode conversion (electron) heating (MC)on Ni transport in low n* ELMy H-modes Density profiles Measured convection coefficient 58144 M.E. Puiatti PoP(2006) 58149 Neoclassical x10 V(m/s) Normalised Ni profile C. GIROUD(EX/8-3) FRI pm r/a r/a • Ni accumulation is anomalous, andmuch lower with RF electron heating than with ion heating • Profile flattening due to outward convection with electron heating Reversal of pinch with e-heating theoretically ascribed to effect of parallel velocity fluctuations with R/LTe driven TEM modes ITER-like ICRH antenna will extend capability

  10. Te modulation experiments show ITB as a narrow layer with reduced heat diffusivity 60 200 150 Pulse No: 62077 40 ITB [eV] 100 Amplitude 20 50 [deg] ] 3 0 0 Phase 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 MW/m Fast wave 2 [10 Mode conversion RF P b) R[m] P. Mantica PRL (2006) • Modulated RF power deposited either side of ITB (at centre and at R=3.6m) • Heat wave propagates towards ITB from both sides • Heat wave amplitude (red) damped strongly when wave reaches ITB • Phase (blue) rises when heat wave approaches ITB, showing heat wave slows down Amplitude and phase of propagating heat wave in plasma with an ITB • ITB is a narrow layer with reduced heat diffusivity • Indication of region with turbulence stabilised and loss of stiffness

  11. ITB forms when qmin exists and approaches (rather than reaches) an integer value S.E. SHARAPOV (EX/P6-19) FRI am Te at various major radii, R, showing formation of an ITB ITB formation slightly ahead of Alfvén Cascades (marking qmin= integer) Pulse No: 61347 qmin reaches 2 Start of ITB formation tAC-tITB(s) Te (keV) Case number Time (s) • Alfvén cascades seen simultaneously on microwave interferometer, O-mode interferometer, X-mode reflectometer (not shown), and magnetic probe • ITB formation starts before q=2 surface enters plasma

  12. Measured poloidal velocity in ITB much higher than neoclassical estimates T. TALA (EX/P3-16) WED pm Ion temperature profiles during ITB formation Poloidal velocity from charge exchange, during ITB formation V (km/s) Ti (keV) Rmid(m) Rmid(m) • Measured poloidal velocity in ITB layer (60km/s) highly anomalous, far higher than neoclassical (~5-10km/s) • ITB layer with steep temperature gradient K. Crombie PRL (2006) • Er and ExB shear much larger with measured Vq • Weiland model with measured Vq (rather than neoclassical) matches experimentbetter

  13. #66560, 5.548s 150 kJ ELMs ELMs can cause damage and must be controlled R.A. PITTS (EX/3-1) WED pm Type I ELMs on ITER could expel transiently 3-8% of 350MJ stored energy  0.6-3.4MJm-2 New fast IR camera Type I ELM energy deposition in the JET MarkII SRP gas box divertor Type I ELMs on JET • ELM energy depositon on inner divertor ~ 2 x outer divertor • Load between ELMs on outer divertor • May relax outer divertor load on ITER 1MJ  0.2MJm-2 on divertor  25000C • Filamentary power deposition • Clear field aligned structures

  14. Passive ELM control with high frequency, small Type I ELMs at low ne (*), high  andq95~4-5 ELM frequency vs. q95 ELM frequency (Hz) TELM/Tped q95 q95 Courtesy of A. LOARTE (2006) High and low d configurations, exploring small Type I ELMs A. LOARTE (IT/P1-14) TUES am TELM/Tpedvs. q95 Height (m)  R (m) • TELM/Tped decreases suddenly at q95 ~ 4.2 and fELM increases • Small ELMs (DWELM/Wped < 5%) obtained with low n* at high  q95 • Not seen at low d More highly shaped plasma at higher q95  “convective” ELMs • At high  small, high frequency Type I ELMs seen at high q95 • Indication of threshold at q95~ 4.2 Cost: high q95 low tE for given B  Combine with improved core for improved confinement

  15. Passive ELM control by plasma shaping, similar to ASDEX Upgrade with QDN 2.5 D 1019m-3 nped also constant <ne> 67911 0 1 H98 0.95 Magnetics 1ms MJ Wtot 0 (a.u.) D 28 29 30 31 32 Time (s) U L k Dsep(mm) 62430 0.5 0.37 1.72 ≤10 66476 0.34 0.4 1.79 ≈ 6 Courtesy of R.J. Buttery et al (2006) Previous JET studies gave only transient Type II behaviour. Refined shape leads to stationary benign ELM regime with good confinement Magnetic configurations in new and previous JET studies Turbulent magnetic fluctuations coincide with Da bursts • ELM behaviour constant over pulse • Very fine scale activity - distinct ELMs almost indistinguishable Blue: New #66476 Red:Previous experiment #62430

  16. Active ELM control at >30MW with an ITB and neon seeding Pulse characteristics Pulse No: 67869 1.9MA/3.1T Divertor radiation Between ELMs (no neon seeding) Z (m) With neon seeding Z (m) R (m) Time (s) X. LITAUDON (EX/P1-12) TUES am D. MOREAU (EX/P1-2) TUES am JET AT database quasi-stationary (/E>10) pulses at high N and high  bN Target for JET-EP2 AT regimes with 45MW planned power upgrades • ELM control with Neon (4-8s) Prad~17MW dithering H-mode • B~3.1T, I~1.9MA, q95~5 PNBI~19.5MW, PICRH~8MW, PLHCD~3.2MW Wdia~5.6MJ, bN~2

  17. Material erosion, migration and deposition are key to fuel retention Measurement Edge 2D modelling Tile 1 Tile 8 2.7% 6.1% Tile 3 13CH4 10.9% 0.5% Tile 7 3.8% 2.5% Tile 5 SRP Tile 4 Tile 6 A. KIRSCHNER (EX/3-5) WED pm Location Behaviour • Inner divertor • Outer divertor vertical tiles • Outer divertor base plate • Remote areas • Deposition dominated • Erosion dominated • Heavy erosion of W stripe (200mm suggested for ITER like wall) • Deposition dominated • Material transport sensitive to magnetic configuration • Complex migration pattern • Fuel retention in divertor (mainly due to co-deposition) is 2.7% of input • (see also T. LOARER (EX/3-6) WED pm) • Main chamber, tile gaps and SRP contributions not included(see also M. RUBEL (EX/P4-24) THU am) • 13CH4 injected in reproducible ELMy H-modes • Quartz Microbalance measurements • 3mm thick W stripe on Tiles 1 and 8 • Post mortem analysis of tiles

  18. Summary and conclusions (1) • Hybrid performance similar to H-mode at q95~4 and slightly better at q95~3 with bN~3 and ~75% Greenwald density New results on Hybrid • ITBs extended to lower q95 (5), higher power (32MW), high edge and core densities and good ELM control with neon injection New results on ITB • neff* most important parameter for density peaking • Peaking factor >1.35 expected for ITER • Impurity transport anomalous, with mild accumulation which can be controlled with electron heating • ITER-like ICRH Antenna to extend density peaking andimpurity control to higher power / lower fuelling Density peaking and impurity control • Core MHD (sawteeth and tornado modes) expel fast particles • ITER-like ICRH antenna to extend control capability for fast particle MHD and transport losses by localised current drive Core MHD and fast particles

  19. Summary and conclusions (2) • Non-stiff profiles with reduced diffusivity in ITB layer • Form slightly ahead of qmin reaching integer value • May be sustained by high ExB shear with observed poloidal velocity significantly greater than neoclassical • Potential access to ITER regime with planned powerupgrades (Ibootstrap and ntET increasing together) ITB physics • ELMs must be ameliorated for ITER • Passive control at high d and q95 (small high frequency Type I) • Passive control with shaping (similar to Type II on AUG) • Active control with Neon injection (ITB with Type III?) New results on passive and active ELM control • Erosion of outer divertor, strong parallel flow in SOL, deposition on inner divertor; sensitive to magnetic configuration • Fuel retention at 3% on JET under C-dominated conditions Material erosion, deposition and migration Need to test ITER wall materials under high performance conditions, as foreseen in longer-term JET programme in support of ITER (Beryllium wall, Tungsten divertor, 45MW heating power)

  20. EFDA-JET contributions to this conference MONDAY AM M. WATKINS (OV/1-3) TUESDAY AM F. CRISANTI* (EX/P1-1) D. MOREAU (EX/P1-2) R.V. BUDNY* (EX/P1-5) X. LITAUDON (EX/P1-12) C. F. MAGGI* (IT/P1-6) A. LOARTE (IT/P1-14) T. HENDER* (IT/P1-21) A. MURARI (IT/P1-23) WEDNESDAY AM H. MAIER* (IT/P2-4) WEDNESDAY PM R. A. PITTS (EX/3-1) A. KIRSCHNER (EX/3-5) T. LOARER (EX/3-6) D. McDONALD* (EX/P3-5) T. TALA (EX/P3-16) * Not referred to in presentation OV/1-3 THURSDAY AM M. RUBEL (EX/P4-24) THURSDAY PM H. L. BERK * (TH/3-1) FRIDAY AM F. PORCELLI (EX/7-4RA) J. ONGENA (EX/P6-9) S. E. SHARAPOV (EX/P6-19) T. A. K. HELLSTEN* (EX/P6-21) V. NAULIN* (TH/P6-22) FRIDAY PM C. GIROUD (EX/8-3) H. WEISEN (EX/8-4) T. C. HENDER* (EX/8-18) V. A. YAVORSKIJ * (TH/P6-7) SATURDAY AM V. PARAIL* (TH/P8-5)

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