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Japan Atomic Energy Agency

Japan Atomic Energy Agency Naka Fusion Institute. Dependence of H-mode pedestal and heat transport on toroidal rotation in JT-60U. H. Urano, H. Takenaga, T. Fujita, Y. Kamada, K. Kamiya, Y. Koide, N. Oyama, M. Yoshida and the JT-60 Team. Japan Atomic Energy Agency.

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Japan Atomic Energy Agency

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  1. Japan Atomic Energy Agency Naka Fusion Institute Dependence of H-mode pedestal and heat transport on toroidal rotation in JT-60U H. Urano, H. Takenaga, T. Fujita, Y. Kamada, K. Kamiya, Y. Koide, N. Oyama, M. Yoshida and the JT-60 Team Japan Atomic Energy Agency The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 1

  2. P - N B I T - N B I J T - 6 0 P Introduction # 6 # 3 , 4 JT-60U has 11 PNBs (~85keV) and 2 NNBs (~350-420keV). # 7 , 8 P - N B I # 2 2 ctr - tang. PNBs (~4.5MW) P - N B I Widely variations in combination of tang. (co/bal/ctr) and perp. injection. After the installation of FSTs, accessible dynamic range of VT has become extended towards co-direction. C T R d i r . I p C O d i r . 2 co - tang. NNB (4MW) 7 perp . PNBs T - N B I 2 co-tang. PNBs (~15.75MW) P - N B I - N B I (~4.5MW) # 9 , 1 0 # 1 3 , 1 4 # 1 2 Energy confinement is improved with toroidal rotation in co-direction during conventional ELMy H-mode plasmas. However, the mechanism how this confinement improvement is obtained with the change of toroidal rotation is not yet clear. H. Shirai et al, NF 39 (1999) 1713 H. Urano et al, NF 47 (2007) 706 The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 2

  3. b pol ETB heat flux Q(r ) V (r ) ? T stiffness p, T boundary µ T(r ) T ped condition Pedestal 0 1 r/a Objectives b pol W = W + W th ped core e.g. L , … T core resilience c (r ), T(r ), n(r ) , … B.C. ELM ? pedestal Locally affected in H-modes? ELM D n , T , , … ped ped ped V (r ) T Clarify the mechanism of energy confinement improvement with co-toroidal rotation in conventional ELMy H-modes. (1) Dependence of H-mode pedestal and ELMs on edge toroidal rotation (2) Dependence of heat transport in the plasma coreon toroidal rotation profile. The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 3

  4. 1.5 1 0.5 0 0 2 4 6 8 10 12 Experiments on power scan with the variation of toroidal momentum source Total and thermal stored energy become higher when co-NBI is applied. co-NBI bal-NBI ctr-NBI 15 PNBI perp. NBs [MW] Line-averaged ne does not change in the variation of tang. NBs. 0 tangential NB 2 neTL [1020m-2] LH transition occurs with lower heating power in case of ctr-NBI. 0 3 WDIA [MJ] 0 1.5 bpol co-inj. 0 200 4 fELM Da (co-NBI) [Hz] [a.u.] bal-inj. 0 0 200 4 fELM Wth [MJ] (bal-NBI) Da ctr-inj. [Hz] [a.u.] 0 0 200 4 fELM (ctr-NBI) Da [Hz] [a.u.] 0 0 4 5 8 9 6 7 time [s] PABS [MW] The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 4

  5. 100 80 60 40 20 -1 0 1 0 -1 0 1 ELM frequency becomes lower and ELM energy loss becomes larger with co-toroidal rotation co-NBI At a given Psep, ELM frequency fELM is clearly reduced as the toroidal rotation increases in co-direction. bal-NBI ctr-NBI fELM [Hz] Psep ~ 5MW, ne ~ 2x1019m-3 VTped [105m/s] With increasing toroidal rotation towards co-direction, ELM energy loss DWELM clearly becomes larger with the decrease of fELM. 10 co-NBI 8 bal-NBI ctr-NBI 6 DWELM /Wped [%] 4 Psep ~ 5MW, 2 ne ~ 2x1019m-3 0 VTPED [105m/s] The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 5

  6. Large ELM affected area in case of co-NBI In case of co-NBI, ELM frequency is lower and drop of edge Te profile becomes larger. ELM affected area also extends more inward in case of co-NBI. The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 6

  7. Pedestal pressure enhanced with increased bpol during type-I ELMy H-mode Enhanced bpol with sufficient central heating can increase the height of the H-mode pedestal during type-I ELMy H-mode phase. A B C D 15 PNBI 10 [MW] 5 co-NBI 0 3 2 neTL 2 [MJ] [1020m-2] 1 WDIA 1 0 0 bp 2 1 Da [a.u.] 1 0 0 2 ne 1 [1019m-3] [keV] 1 Te 0 0 4 5 6 8 7 9 time [s] P. B. Snyder et al, H-mode WS (2007) Ip = 1.2MA, BT = 2.6T, q95 ~ 4, d ~ 0.35 The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 7

  8. 2 5 co-NBI co-NBI bal-NBI 4 1 ctr-NBI bal-NBI 3 VT [105m/s] Qi/ni [Wm3] 0 2 cCTR -1 1 ctr-NBI r/a = 0.6 cCO -2 0 0 2 4 6 0 0.2 0.4 0.6 0.8 1 8 r/a dTi/dr [keV/m] 8 8 co-NBI bal-NBI bal-NBI 6 6 ctr-NBI ctr-NBI Heat Flux Qi [MW] ci [m2/s] 4 4 2 2 co-NBI 0 0 0.2 0.8 0.2 0.4 0.6 0.8 r/a r/a Reduced heat diffusivity at the plasma core in case of co-NBI TG becomes larger at the plasma core when co-NBI is applied. Core heat transport given by Q/(nT) in a steady state is enhanced when ctr-NBI is applied. Heat diffusivity is reduced at a given Pabs in case of co-NBI. Is core TG scale length shortened by enhanced VT in co-direction? The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 8

  9. 10 co-NBI 8 bal-NBI ctr-NBI 6 Ti [keV] 4 2 0 10 r/a 1 Ti [keV] Logarithmic plot 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 r/a Self-similar temperature profile raised with co-NBI leading to highly sustained energy Core temperature increases throughout minor radius when co-NBI is applied. Heat transport varies with sustaining self-similar temperature profiles in the variations of toroidal rotation. Does increased pedestal temperature with co-toroidal rotation play a role as a key factor for better confinement? The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 9

  10. -1 -0.5 0 0.5 1 Pedestal structure varies together with edge toroidal rotation bpol = 1.3 Pedestal temperature is increased with toroidal rotation. 3 co-NBI bal-NBI ctr-NBI 2 Steep dT/dr in the ETB layer might be caused by increased bpol in case of co-NBI. Ti [keV] bpol = 1.1 1 Pedestal pressure increases weakly with the increase of VTped into co-direction. 0 20 15 10 5 0 -5 Distance from separatrix [cm] 8 co-NBI bal-NBI 6 Examine heat transport in the plasma core when boundary condition is fixed in cases of co-and ctr-NBI. pped [kPa] 4 ctr-NBI 2 Pabs ~ 8MW 0 VTped [105m/s] The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 10

  11. Identical temperature profiles for cases of co- and ctr-NBI atfixed Tped adjusted by density When density is raised in co-case to reduce Tped to the level of ctr-case, identical T profiles are obtained in spite of totally different VT profiles. Heat diffusivities are also similar at Q/n ~ const. because of similar T profiles (dT/dr = const.). The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 11

  12. 5 4 3 2 10 1 0 1 0 0.2 0.4 0.6 0.8 1 Difference of TG scale length is small in the variations of VT profiles TG scale length does not clearly change with VT and remains roughly constant in core region. co-NBI bal-NBI ctr-NBI Qi /ni [10-13Wm3] r/a = 0.6 Heat flux is enhanced while sustaining self-similar Ti profile in the variations of toroidal rotation. 0 1 2 3 Ti /Ti [m-1] High pedestal temperature is a key factor for confinement improvement with toroidal rotation. Ti [keV] r/a The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 12

  13. Summary: Schematic view of H-mode confinement When VT increases in co-direction, pedestal pressure becomes larger. Heat transport in the core is reduced with toroidal rotation while sustaining self-similar temperature profile with higher Tped. Energy confinement in the variation of VT is determined by increased pedestal and reduced transport brought on by stiffness in standard H-mode plasmas. b pol b pol ETB heat flux Q(r ) W = W + W th ped core e.g. L , … stiffness T core p, T resilience c (r ), T(r ), n(r ) , … boundary µ T(r ) T ped condition B.C. ELM pedestal very weak in standard H-mode ELM D Pedestal n , T , , … ped ped ped 0 1 V (r ) r/a T The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 13

  14. 1.8 1.6 1.6 1.4 1.4 1.2 1.2 1 1 0.8 0.8 0.6 -3 -2 -1 0 1 2 3 -3 -2 -1 0 1 2 3 -3 -3 -2 -2 -1 -1 0 0 1 1 2 2 3 3 Electron density profiles are insensitive to torodial rotation except outward shifted case Density profiles or peaking factor does not largely change with VT at the plasma core. bal-NBI co-NBI ne (r=0.2a) / neU2 ne (r=0.2a) / neU2 ctr-NBI However, in case of outward shifted large volume plasma, density profile tends to be peaked at the center when ctr-NBI is applied. VT (r=0.2a) [105m/s] VT (r=0.2a) [105m/s] 3 3 Effect of fast ion loss? Er, impurity, … 2 2 neU2 [1019m-3] neU2 [1019m-3] 1 1 Operational range of ne remains roughly constant. 0 0 VT (r=0.2a) [105m/s] VT (r=0.2a) [105m/s] The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 14

  15. 10 10 10 8 8 8 6 6 6 4 4 4 2 2 2 0 0 0 TG scale length in DB analysis Enhanced heat flux at global TG boundary in the plasma core is similar in the variations of the direction of tang-NBI. Ti0.2a– Tiped X = ~ 1/LTi 0.7a x 0.5 x (Ti0.2a + Tiped) Larger volume plasmas have more stiff Ti profiles against heating power. Remove the effect of mean dT/dr caused by power deposition. Y = Pabs – Prad– dW/dt co-NBI bal-NBI ctr-NBI Y Y Y 0 1 2 3 0 1 2 3 0 1 2 3 X X X The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 15

  16. 4 2 0 (A) co - NBI 2 2 pedestal shoulder ] keV [ ped 1 1 i T (B) ctr - NBI n ~ 1.5x10 m ped 19 - 3 e 0 0 0.1 0.1 0.05 0.05 0 0 - - 0.05 0.05 distance from separatrix [m] Pedestal pressure tends to increase weakly with toroidal rotation into co-direction 10 10 Pedestal pressure increases weakly with the increase of VTped into co-direction at fixed power. (A) 8 8 (B) ] 6 6 kPa [ pped 4 Type-I ELMs 2 Psep ~ 5MW 0 - - 1 1 - - 0.5 0.5 0 0 0.5 0.5 1 1 VTped [105m/s] Compare the pedestal profiles with VTped into co- and ctr-direction. Height and width of the H-mode pedestal of Ti profile becomes greater when co-NBI is applied. The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007 JT-60U Tokamak: p. 16

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