1. JT-60U -1- Access to High  p (advanced inductive) and Reversed Shear (steady state) plasmas in JT-60U S. Ide for the JT-60 Team Japan Atomic Energy Agency the 7 th Integrated Operation Scenarios Topical Group Meeting Kyoto University, Kyoto, Japan, 18th – 21st October 2011

2. JT-60U -2- high  p and RS plasmas in JT-60U How to access these plasmas? In JT-60U, the AT development has been pursued base on two types of internal transport barrier (ITB) plasmas mainly with pedestal. 10 pressure  weak strong ITB H-mode pedestal 1 2 3 10 q  2 3 4 10 q  High  p plasma (since 1994) Reversed shear (RS) plasma (since1996) Monotonic/weak shear,  N  5, f BS  70%, full CD ITB are sometimes very weak Candidate for advanced inductive RS w or w/o current hole,  N  2.5, f BS  80%, full CD Strong ITB Candidate for steady state

3. JT-60U -3- high  p plasmas monotonic-weak shear (q min ~1-1.5) weak-moderate ITB + pedestal  N ≤ ~3 (for longer sustainment), <~5 (very short) q 95 ~2.5 – 4.5 (roughly) Can be fully non-inductive with f BS ~50% Not sensitive care is required at ramp-up phase. NB injection start, just before reaching flattop or even after. So injected energy during ramp-up is not important. A simple empirical recipes exists –start (strong) NB heating just before sawtooth starts. –central NB deposition is important. –for above two, keeping low density before NB heating is preferred.

4. JT-60U -4- ITBs in a high  p mode

5. JT-60U -5- ITER Advanced Op. Inductive Op. sustained duration (s) sustained  N time (s) I p (MA) P NB (MW) n e /10 19 (m -3 ) E44092, B t = 1.56 T NN D  (a.u.) T e,i (keV)  N =2.3 sustained for 22.3s(~13.1  R ) P-NB N-NB TeTe TiTi  N =2.3 Long Sustainment of High  N In ITER,  N H 89p /q 95 2 = 0.4: standard (Q=10) and =0.3: steady state (Q=5) => ITER Hybrid operation q 95 ~3.1- 3.2 H 89p ~1.9  N H 89p /q 95 2 > 0.4  N =2.5 and 2.3 f BS ~35-40%  N = 2.3x22.3s  N =2.5x16.5 s T. Suzuki (EX/1-3, Tue.)  R : Dr. D. R. Mikkelsen Phys. Fluids B 1 (1989) 333.

6. JT-60U -6- W dia (MJ) P abs (MW) P th can be also found by power step-up again no B t dependence time [sec] ITB

7. JT-60U -7- High fusion performance with full CD -High  ~0.34 at high I p =1.8 MA and high power N-NB (5.7 MW)  N =2.3-2.5, HH y2 = 1.2, n D (0)  E T i (0) = 3.1x10 20 m -3 skeV, full non- inductive CD (BS:50%)  was suppressed by tailoring p(r)&q(r) in low collsionality regime (  e *~0.02~ITER).

8. JT-60U -8-  j tot,j BS, j NB (MA/m -2 ) q j NB j BS 8.3s j tot f BS ~45% sustained for 5.8s (~2.8  R ) under nearly full CD in weak shear (q min ~1.5) plasma Weak shear with q min >~1.5 => no NTM.  N ~2.4 (  p ~1.75), f CD >90%(f BS ~50-43%, f BD >52-47%), H H98(y,2) ~1.0  p,  N V loop (V) D  div (a.u.) time (sec) P NB, NNB (MW) NN pp N-NB P-NB nearly full-CD 1MA, 2.4T, q 95 ~4.5 E44104 Y. Sakamoto (EX/4-3, Wed.) Integrated performance the ITER steady state domain

9. JT-60U -9- reversed shear plasmas weakly-strongly reversed shear (q min mostly >2, q 0 ~2 - >10) moderate-strong(box type) ITB + weak pedestal  N ≤ ~2.7 q 95 ~> 4.5 (typically) Can be fully non-inductive with f BS <~85% Empirical recipes –start NB heating as early as possible. For this divertor configuration stars at very early of a discharge (<0.5s from breakdown). –central NB deposition is important. –NB heating at early time, when q is reversed, triggers ITB. The ITB raises the BS current at ITB. The BS current enhances or keep the q profile reversed.

10. JT-60U -10- reversed shear plasmas ITB formation –Reversed shear is believed to be an enough condition for ITB formation, but sometimes not sufficient. –P th to form T i ITB seems to be lower for lower I p. Once ITB is formed it is easier to maintain the reversed shear. Therefore, typical recipe to establish a good RS discharge is early NB injection. –For T e ITB formation, P th seems to be very low or even almost zero if the q profile is reversed. –W/O ITB formed very early in a discharge, target reversed q profile can hardly be maintained until Ip flattop. Therefore early NB injection is required. –However with LHCD, reversed q can be maintained and late ITB formation is possible.

11. JT-60U -11- f BS ~75% sustained for 7.4s (2.7  R ) under nearly full CD in reversed shear plasma Very high confinement characteristics: H H98(y,2) ~1.7 (H 89p ~3.0), f BS ~75%, f BD ~20%,  p =2.2-2.3,  N ~1.7, n e /n GW ~0.55 Although q 95 is yet high, demonstrates steady state with high f BS I p (MA)  p,  N V loop (V) D  div (a.u.) time (sec) P NB (MW)  T i (keV) q 0.8MA, 3.4T,q 95 ~8.6 Y. Sakamoto (EX/4-3, Wed.)

12. JT-60U -12- T i ITB formation  NB power scan  Experimental condition: B T ~3.7T, I p ~1.3MA, q 95 ~5,  ~0.2, n e ~1.0x10 19 m -3, Balanced momentum injection. NB power (P NB ) was varied from 2 to ~17MW in PS and RS plasmas. Change in T i profiles are significantly different in both PS and RS plasmas. RSPS

13. JT-60U -13- T i ITB formation depends on I p

14. JT-60U -14- Magnetic shear is a key factor for T e ITB formation Inverse scale length of T e (L Te -1 ) for RS plasmas increased gradually with P EC. T e ITB was formed without T i ITB in RS region. Gradual increase suggests that absence of threshold power for T e ITB formation. Inverse scale length of T e (L Te -1 ) for PS plasmas stays constant with increasing P EC. T e ITB was not formed without T i ITB in PS region. The threshold power for PS is large compared with that for RS. RSPS L Te -1 =-gradT e /T e

15. JT-60U -15- ECH to raise T e Before ECH faulted, q profile is reversed. But, q min is lower and RS region is smaller. <= due to peaked T e, in outer region where T e is not high current penetration is not retarded.

16. JT-60U -16- off axis LHCD with LHCD (~ 1.5 MW), well reversed q profile with large RS region was obtained.

17. JT-60U -17- comparison of three cases in LHCD case, –q min is well maintained high. –wide reversed shear region. –low density => matter of CD efficiency and power.

18. JT-60U -18- Summary High  p –Simple recipe: apply central heating (just) before ST. –P th exists, but parameter dependences are not clear yet. Reversed shear –For T e ITB, low or no P th., while for T i P th exists and lower for lower I p. –JT-60U recipe is to apply NB heating as soon as possible at ramp- up. But may suffer, too strong ITB or current hole.