1 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Free boundary simulations of the ITER hybrid and steady-state scenarios J.Garcia 1, J. F. Artaud 1, K. Besseghir 2, G. Giruzzi 1, F. Imbeaux 1, J.B. Lister 2, P. Maget 1 1 CEA, IRFM, F Saint-Paul-lez-Durance, France. 2 Ecole Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confédération Suisse, CH-1015 Lausanne, Switzerland

2 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Outline Background: motivation New ITER hybrid scenario MHD analysis Coils post processing analysis Sensitivity analysis Free boundary simulation Steady-state scenario Conclusions

3 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Hybrid scenario Hybrid scenario analyzed with GLF23 transport model and optimized in order avoid q=1 by still having Q=5 For Tped=4 keV and flat density profile the q=1 surface can be strongly delayed. The q profile shape enhances fusion performance but......β N =2 with H 98 =1, so roughly speaking it is an H mode at low current What are the requirements for a hybrid scenario in ITER similar to those in present day machines? Could the device handle these scenarios? In density peaking essential? Plasma shaping? High H 98 ? J. Citrin et al., Nucl. Fusion 50 (2010)

4 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Steady-State scenario Steady-state scenario with strong ITB developed Simple core transport model:  e =  i =  i,neo (1+3  2 ) F(s) (m 2 /s) F(s): shear function allowing an ITB formation for s < 0 MHD problems quickly appear: oscillatory regimes can overcome them but require difficult time control Steady-state scenarios with no ITB, low pedestal and good q profile properties are possible? What are the requirements? J.Garcia et al., Phys. Rev. Lett. 100, (2008) J.Garcia et al., Nucl. Fusion 50 (2010)

5 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Simulations of new ITER hybrid scenario I p = 12 MA, B T = 5.3 T dI p /dt= 0.18 MA/s, B T = 5.3 T, f G =0.4 during ramp-up. f G =0.85 flat-top phase EC wave launch: top launchers, 8MW during ramp-up, 20MW flat-top (equatorial launchers) ICRH: 20 MW, NBI: 33MW (off-axis and on-axis) n e profile fixed, peaked profile, n e (0) ≈ m -3  ped ≈ 0.95, n ped ≈ m -3, T ped  4.5 keV Bohm-GyroBohm transport model during ramp-up H 98 =1.3 with Bohm-GyroBohm shape for flat-top phase

6 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Simulations of new ITER hybrid scenario The current configuration aims to have the bulk of the off- axis current inside ρ=0.5 Only 16.5MW of off-axis NBI used The on-axis NBI power helps to peak the pressure profile Peaked density profile (peaking factor 1.4), checked with GLF23 The ICRH power is on-axis for the electrons and off-axis for the ions β N =2.65, β p =1.45, Q=8

7 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Simulations of new ITER hybrid scenario Ini=8.65MA (fni=79.6%), Iboot=4.4MA (fboot=41.0%), Inbcd=3.5MA (fnbcd=31.8%), Ieccd=0.75MA (feccd=6.8%), There is almost no evolution of q from 500s until t=1200s q profile remains above 1 and almost stationary with a flat core profile Ramp-down strategy: Avoid abrupt transition to low beta regime Suppression of NBI and ICRH powers at the beginning of the ramp-down Electron density ramped-down H mode sustained with ECRH and alpha power When alpha power is low, transition to L mode No flux consumption during the H mode

8 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA MHD analysis Linear MHD analysis at the plasma edge done with MISHKA The hybrid scenario is linearly stable. The pedestal assumptions seem reasonable Core MHD analysis to be done

9 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Coils analysis Post processing coils analysis done with the code Freebie The scenario seems globally acceptable as it is in the CRONOS simulation, from the PF coils point of view (coils limits in green). Some limits are approached or violated transiently, but there is margin to avoid it by slightly modifying the plasma shape evolution.

10 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Sensitivity analysis 1: Plasma shape t=850s Alternative shape used for q 95 =3.5 The plasma reaches q=1 at t=850s Two different effects: lower q with lower elongated plasma lower bootstrap current due to lower q

11 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Sensitivity analysis 2: Density peaking Different density peaking factors considered: 1.4, 1.25, 1.1 The bootstrap current profiles changes especially in the region 0<ρ<0.5 This change tailors the q profile which falls below 1 and becomes monotonic for the flat density case

12 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Sensitivity analysis 3: H 98 (y,2) factor Sensitivity to H 98 (y,2) analyzed by repeating the simulation with H 98 (y,2)=1 The bootstrap current profile drops in the full plasma column This change tailors the q profile which falls below 1 and becomes monotonic The situation is similar to the case with flat density

13 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Self consistent free boundary simulation with CRONOS-DINA-CH The simulation is repeated in a self-consistent way with the free boundary code CRONOS-DINA-CH Current and temperature profiles are simulated. Density is prescribed The plasma is initiated in an inboard configuration The shape can be controlled even at the transition to a high beta plasma at the L-H transition

14 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Self consistent free boundary simulation with CRONOS-DINA-CH The coils are always within the limits, no transient saturation found The evolution of q is very sensitive to the shape of the plasma and to the non-inductive currents. Real time control needed (not done yet)

15 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Simulations of ITER steady-state scenario I p = 10 MA (q 95 = 4.85), B T = 5.3 T dI p /dt= 0.18 MA/s, B T = 5.3 T, f G =0.4 during ramp-up. f G =0.9 flat-top phase EC wave launch: top launchers, 8MW during ramp-up, equatorial launchers 20MW flat-top ICRH: 20 MW, NBI: 33MW (off-axis and on-axis) LHCD: 15 MW n e profile fixed, peaked profile, n e (0) ≈ m -3  ped ≈ 0.95, n ped ≈ m -3, T ped  3.7 keV Bohm-GyroBohm transport model during ramp-up H 98 (y,2) =1.4 with Bohm-GyroBohm shape for flat-top phase

16 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA Simulations of ITER steady-state scenario β N =2.60, β p =1.66, Q=5 The scenario is similar to a hybrid one but with q min ≈1.5 The inclusion of LH is essential to reach V loop =0

17 J. Garcia ITPA-IOS meeting Kyoto October 2011 Association Euratom-CEA conclusions A new ITER hybrid scenario is created with two goals: Understanding the physical requirements in order to establish a hybrid scenario similar to present day machines Analyze whether the ITER device can handle it The q profile can be sustained above 1 with a flat profile for 1200s The scenario is linearly MHD stable and feasible from the coil system point of view The scenario is found to be very sensitive to the plasma shape, density peaking and H 98 (y,2) factor, through the bootstrap current A free boundary simulation has been carried out with the full shape evolution for the scenario. No problems have been found for the coil system A steady-state scenario similar to the hybrid one has been also developed. Unlike in the hybrid case, the inclusion of a LH system is essential to reach Vloop=0