Progress in understanding W control using ICRH in the JET-ILW tokamak P.Mantica 20 th US-EU TTF Workshop, Salem, MA, US 28 th April-1 st May 2015
Acknowledgements P.Mantica1, C.Angioni2, R.Bilato2, F.Casson3, M.Valisa4, E.Belonohy2, C.Giroud3, M.Goniche5, N.Hawkes3, E. Lerche6 and JET Contributors* EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB, UK Istituto di Fisica del Plasma P.Caldirola, Consiglio Nazionale delle Ricerche, Milano, Italy 2 Max Planck Institut fur Plasmaphysik, D- 85748, Garching, Germany 3 CCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK 4 Consorzio RFX, Consiglio Nazionale delle Ricerche, Padova, Italy 5CEA, IRFM, F-13108 St. Paul Lez Durance, France 6LPP-ERM-KMS, Brussels, Belgium 1 * See the Appendix of F. Romanelli et al., Proceedings of the 25th IAEA Fusion Energy Conference 2014, Saint Petersburg, Russia P.Mantica US-EU TTF Salem (US) 1st May2015 Page 2
OUTLINE W accumulation in NBI only JET plasmas: results and understanding Understanding possible effects of ICRH on W accumulation First results of ICRH application in Hybrid and Baseline H-modes Future plans in view of achieving stable scenarios for JET D-T campaign P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 3
W accumulation in NBI only JET plasmas W accumulation due to neoclassical transport, strongly enhanced by centrifugal effects causing poloidal asymmetries due to W localization on the LFS Neoclassical convection turns to inward due to density evolution from hollow to peaked after L-H transition In high collisionality scenarios, in addition, temperature screening is decreased by centrifugal effects [C.Angioni et al., Nucl Fus 2014; C.Angioni et al, APS 2015, Phys Plasmas in press] è Even increasing ELM frequency with enhanced gas puff, a Hybrid scenario does not last with improved confinement longer than 2-3 s, whilst Baseline scenarios can leave longer due to the presence of sawteeth. è W accumulation is a major obstacle to reaching good performance in view of the D-T campaign! P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 4
Example of accumulation in NBI only plasmas 83351 Baseline H- mode This type of evolu>on is typical of Baselines and Hybrids P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 5
NEO+GKW simulations in NBI only early late P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 6
Time evolution of Hybrid vs Baseline W core transport physics is the same in both scenarios Due to lower collisionality, Hybrids have more peaked ne, but also more peaked Ti and better neoclassical screening Baselines benefit of regular sawteeth à overall Hybrids with NBI only are ALWAYS non stationary and performance decreases after ~2 sec due to increasing W accumulation, whilst Baselines have stationary lower performance still with peaked W 84669 Hybrid 2T/1.9 MA ne r/a=0 r/a=0.45 r/a=0.85 ne 83351 Sta H- mode 2.5 T/ 2.75MA SXR line integrals r/a=0.4 β N H98 r/a=0 r/a=0.22 β N H98 SXR line integrals 4.5 5.0 5.5 6.0 8 9 10 11 12 13 P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 7
Need to use ICRH! Both scenarios are presently not suited to extrapolate to D-T expected performance: Target D-T: Pfus~ 15 MW for 5 sec Present Hybrid: Pfus~ 5.5 MW for 0.5 sec Present Baseline: Pfus~ 3.2MW for 3 sec/2.2 MW steady Extrapolation to full power of 40 MW (present was ~25 MW): Hybrid : Pfus~ 13 MW for? sec Not accoun>ng for isotope and α- Baseline : Pfus~ 8 MW steady par>cle effects Use of ICRH is the only option for controlling W on JET in the core Needed in Hybrids to achieve stationarity and in Baselines to alleviate the need for high gas puff detrimental for pedestal performance leading to H98~0.8 P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 8
Effects of ICRH on W transport ICRH acts on W transport through a number of mechanisms: Through plasma profile modification ü It flattens n e profile leading to reduction of neoclassical V inw ü Under some conditions it can also peak Ti profile leading to reduction of neoclassical V inw ü It increases core heat flux leading to more turbulence and increasing D ü It lowers rotation leading to smaller centrifugal effects and lower neoclassical transport (D&V) Through direct effects on W ü Extra screening associated to minority fast ion temperature leading to less neoclassical V inw ü Anisotropy of minority fast ion temperature T > T modifies poloidal asymmetries and can produce W localization on the HFS. This lowers neoclassical D and increases neoclassical V outw. [F.Casson et al., PPCF 2015, Angioni et al and Belli et al PPCF 2014 for NC theory aspects, Bilato NF 14 on ICRH anisotropy impact) P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 9
Effects of ICRH in Baseline H-mode 2.8 T/ 2.5 MA 85308 NBI=19.1 MW 85307 NBI=14.7 MW ICRH=4.9 MW 42.5 MHz Rres 2.98 m ρ dep ~+0.03 H min ~ 9% ICRH deposi>on and T anisotropy of minority calculated by TORIC/SSFPQL Note: SSFPQL misses finite orbit effects, so it yields an upper es>mate of the temperature anisotropy and of the temperature gradient of resona>ng ions P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 10
NEO+GKW in Baseline H-mode with ICRH Profile modifica>ons lower V inw but are not enough to reverse it. Direct effects of ICRH minority ions are needed to obtain V outw in the central region. Taking into account anisotropy of fast ions, this is combined to a dip in Dneocl which strengthens its effect. In addi>on a general increase of Dturb takes place in the outer region. P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 11
NEO+GKW in Baseline H-mode with ICRH Total D and V profiles with and without anisotropy So the total D and v profiles lead to high screening of the central region (outward V neocl+ low Dneocl in the case with anisotropy) and large turbulent diffusion in the outer region, with resul>ng W profiles going from peaked to hollow in the central region due to ICRH P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 12
Effects of ICRH in Baseline H-mode Calculated 2D SXR emission in good agreement with experiment 85308: NBI ONLY 85307: NBI + ICRH Model Experiment Model Experiment ICRH indeed proves an effec2ve tool to prevent central W accumula2on. P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 13
Mo LBO simulated with NEO+GKW D & V Without anisotropy effects T H =T eff Main changes due to ICRH in Mo transport are increase of Dturb outside ρ=0.2 and reversal of Vneocl inside ρ=0.2. The NEO+GKW coefficients reproduce well the expt >me evolu>on of SXR line integrals aier Mo LBO. P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 14
Mo LBO simulated with NEO+GKW D & V With anisotropy effects 85307 aniso 85307 aniso The central dip in D due to anisotropy slows down penetra>on in the inner region, at variance with experiment. Bejer inves>ga>on of anisotropy effects in T H including finite orbit effects and of sensi>vity to uncertainty in H concentra>on is needed. P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 15
Effects of ICRH in Hybrids 87253 central ICRH+NBI vs 87252 far off-axis ICRH + NBI T H [kev] n e,i [m 3 ] 6 5 4 3 2 x 10 19 1 87253 46.3 87252 46.3 0 0 0.2 0.4 0.6 0.8 r / a 300 Teff 87253 46.3 T 87253 46.3 250 T 87253 46.3 200 150 100 50 Teff 87252 46.3 T 87252 46.3 T 87252 46.3 0 0 0.2 0.4 0.6 0.8 r / a V tor [m/s] T [kev] 9 8 7 6 5 4 3 2 1 0 0 0.2 0.4 0.6 0.8 r / a 3 x 105 2.5 2 1.5 1 Te 87253 46.3 Te 87252 46.3 Ti 87253 46.3 Ti 87252 46.3 0.5 87253 46.3 87252 46.3 0 0 0.2 0.4 0.6 0.8 r / a 2.9 T/ 2.5 MA Raxis~2.98 m 87253 t=6.3 s NBI=22 MW ICRH=4 MW 46.16 MHz Rres=2.85 m HFS ρ dep ~ - 0.14 87252 t=6.3 s NBI=22 MW ICRH=4 MW 51.4 MHz Rres=2.57m HFS ρ dep ~ - 0.4 Hmin ~ 4% ICRH deposi>on and T anisotropy of minority calculated by TORIC/SSFPQL P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 16
Effects of ICRH in Hybrids SXR tomography 87252 off- axis t=6.4 s 87253 on- axis Also in Hybrids on- axis ICRH helps avoiding central accumula>on P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 17
Effects of ICRH in Hybrids 87252 off- axis t=6.4 s 87253 on- axis W concentra>on deduced from SXR tomography W density deduced from SXR tomography is hollow in the onaxis case and peaked in the off-axis case P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 18
NEO+GKW in Hybrids with ICRH 40 20 With ON- axis ICRH 87253 t=6.3 s 87253 46.3 40 20 With OFF- axis ICR 87252 t=6.3 s 87252 46.3 RV W / i NEO (LFS) 0 20 40 60 80 RV W GKW RV W NEO Aniso H RV W NEO Iso T H = T eff RV W / i NEO (LFS) 0 20 40 60 80 RV W GKW RV W NEO Aniso H RV W NEO Iso T H = T eff 100 RV W NEO CF only 120 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 r/a 87253 46.3 100 120 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 r/a 87252 46.3 RV W NEO CF only 10 1 10 1 D W / i NEO (LFS) 10 0 10 1 10 2 D W GKW D W NEO Aniso H D W NEO Iso T H = T eff, CF only 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 r/a In 87253, The anisotropy effect is more important than the temperature screening effect. D W / i NEO (LFS) 10 0 10 1 10 2 D W GKW D W NEO Aniso H D NEO Iso T = T W H eff 0.8 0.4 0.45 0.5 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 r/a In 87252, the anisotropy and minority temperature screening effects are very small compared to 87253. P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 19 1.1 1 0.9
NEO+GKW in Hybrids with ICRH Resul>ng n W profiles Good qualita>ve agreement with experiment only when considering anisotropy effects P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 20
Is time behaviour of Hybrids with ON-axis ICRH more stable? 87252 OFF- axis ICRH SXR line integrals Power 87253 ON- axis ICRH NBI ICRH Indeed ON- axis ICRH maintains the central W under control and keeps some W in the outer region, whilst in the OFF- axis ICRH case the central W runs away and Te drops drama>cally. Te OFF- axis ICRH Good prospects for future developments. 5.5 6 6.5 7 7.5 t(s) 8 Page 21
Is time behaviour of Hybrids with ON-axis ICRH more stable? Longest stable so far ~ 5 s but not at top performance 2.9 T 42.56 MHz Hmin~3.5% Rres=3.09 m LFS ρ dep ~+0.1 ne Te0 r/a=0 r/a=0.85 r/a=0.45 86871 βn Broader power deposi>on also due to worse focaliza>on on LFS SXR line int 6 7 8 t(s) 9 10 11 12 Long phase at top performance not available yet, it is the objec>ve of 2015 campaigns! P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 22
CONCLUSIONS AND FUTURE PLANS W accumulation in JET is dominated by neoclassical transport and due to progressive density peaking after L-H transition ICRH has proven an effective tool to modify neoclassical transport in the central region by a variety of physics mechanisms and so prevent or at least mitigate W accumulation both in Baseline H-modes and Hybrids Optimization of ICRH use and increase of ICRH power is foreseen for next campaigns: ü Fine scan of resonance posi>on in Hybrids to find best effects ü Inves>gate effect of minority concentra>on ü Apply best scheme to high performance Hybrids and Baseline H- modes ü Inves>gate effects of 3He vs H min ü Maximize ICRH power using also ITER like antenna P.Mantica US-EU TTF Salem (US) 28 th April-1 st May2015 Page 23