Advanced Tokamak Research in JT60U and JT60SA


 Elmer Mitchell
 8 months ago
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1 I07 Advanced Tokamak Research in and JT60SA A. Isayama for the JT60 team 18th International Toki Conference (ITC18) December 912, 2008 Ceratopia Toki, Toki Gifu JAPAN
2 Contents Advanced tokamak development in Physics understanding in AT regime Physics assessment for JT60SA Summary JT60SA DEMO ITER
3 Advanced tokamak development in
4 This talk Sakamoto (Thu, AM) Advanced Tokamak research in In ITER & DEMO, simultaneous achievement of  High beta (β N )  High confinement (H H98(y,2) )  High noninductive CD fraction f NI (=f BS +f CD ) with sufficient duration is required In AT research,  High β p Hmode (~ITER Hybrid)  Reversed shear (~ITER SS) have been developed β N N T M ITER SS ITER Hybrid Positive shear JT60SA R W M DEMO Nowall β limit: 34 l i Reversed shear f BS AT target Standard Advanced Progress in ITER Physics Basis, Chap.1
5 β N H H98(y,2) >2.6 was sustained for 25s (~14τ R ) in high β p Hmode plasma β N =2.6, H H98(y,2) = , f BS ~0.4: >~ ITER Hybrid performance Avoidance of NTM onset by p & q optimization: q=1.5, 2 surfaces far from steep p 0.9MA/1.55T, q 95 =3.2, H H ~1, n e /n GW ~
6 Central heating is effective in keeping ITB E45436(2006) E48158(2008) 2008 w/o FST w/ FST ITER Hybrid FST 2006 Fast ion loss has been reduced by installing ferritic steel tile (FST) (2005) Power supply of 3 PERPNBs for central heating was modified for 30s injection (2007) Peaked pressure can be kept with smaller P net
7 Physics understanding in AT regime  NTM suppression  RWM suppression Last shot of (2008/8/29)
8 NTM stabilization with ECCD in Neoclassical Tearing Modes (NTMs)  appear in a high β plasma with positive shear ITER Standard and Hybrid scenarios  set achievable beta at β N <β N ideal  sometimes cause disruption NTM control is important: m/n=3/2 and 2/1 NTM avoidance longpulse highbeta exp. NTM stabilization: ECCD Previous results in with ECCD Stabilization with O1 & X2 ECCD Stabilization with realtime mirror steering Preemptive stabilization Simulation with TOPICSIB code NTM research in Stabilization with modulated ECCD Modulation Frequency [khz] Progress in modulation NTM stabilization Heat wave propagation Year
9 Stabilization effect is significantly affected by the phase difference between db/dt and ECCD Modulated ECCD: phasing is required for Opoint ECCD 0º 90º 180º 0º phase difference: stabilization effect 90º phase difference: no clear effect 180º phase difference: destabilization effect Phasing is important
10 Detailed phase scan showed that phase error should be smaller for effective stabilization ECCD efficiency: η EC Hegna, PoP 97 Perkins EPS 97 Giruzzi, NF 99 50% degradation Opoint ECCD ~exp[t/τ decay ] 300ms B ~ time Modified Rutherford equation dw/dt=f(w) η EC (W) g(w) τ decay : minimum at ~ 10º Opoint ECCD τ decay ~4s for unmodulated ECCD modulated ECCD : > x2 more effective α c Similar to experiments
11 RWM study in Resistive Wall Modes (RWMs)  appear at β N > β N  terminate the plasma by disruption Rotation can stabilize RWM RMW control by V t control : Variety of NBI pattern Previous RWM study Identification of minimum V t for RWM stability V crit t ~0.3% of V A M. Takechi PRL (2007) C β = β N β N β N idealwall β N RWM research in Detailed study on RWM stability (dv t /dr, etc) Sustainment of β N > β N plasma
12 Two new instabilities have been observed just before RWM: EWM and RWM precursor Discharge duration was limited by a variety of MHD instabilities Two new instabilities at β N >β N (1) Energetic particle driven Wall Mode (EWM) directly induce RWM even at V t >V t crit (2) RWM Precursor strongly affects V t profile at q=2, and finally induces RWM Strategy for longer sustainment  Sustain enough V t & dv t /dr to avoid RWM  Reduce perpendicular NB to avoid EWM/RWM precursor G. Matsunaga, IAEA2008
13 High β N (> β N ) was sustained for ~5s (~3τ R ) β N ~3.0 (C β ~0.4) was sustained by keeping V t > V t crit Sustained duration: ~5s (~3τ R ) limited by increase of β N due to gradual j(r) penetration f NI >80% and f BS ~50% (ACCOME code calculation) Successful sustainment by RWM suppression β N ~5s (~3τ R ) High β N regime above β N has been extended
14 Physics assessment for JT60SA
15 JT60SA program JT60SA (JT60 Super Advanced) Combined program of  ITER Satellite Tokamak Program of JA and EU  Japanese National Program Mission of JT60SA Early realization of fusion energy by  supporting exploitation of ITER  research toward DEMO Target area of JT60SA plasma Wide range of operational regime  Breakeven class plasmas at I p <~5.5 MA  High β N fullcd plasmas for 100 s Wide range of plasma equilibrium  High shape parameter: S~6  Low aspect ratio: A~2.5 S=(I p /ab)q 95 A 1 {1+κ 2 (1+2δ 2 )} Better stability with higher A 1, κ, δ a measure of stability improvement β t (=Sβ N /q 95 ) increases with S
16 Main parameters in JT60SA Active MHD stabilization tools  110GHz ECRF for NTM  Invessel coils for RWM Nominal Parameter Major radius R [m] Minor radius a [m] Plasma current I p [MA] Toroidal Field B t [T] Plasma Volume [m 3 ] Greenwald density [10 20 m 3 ] Shape Parameter S Flattop [Wb] TF Ripple at R+a Aspect ratio A 2.5 Elongation κ x Triangularity δ x Safety factor q 95 ~ ~ ~8 0.85%
17 Profiles in full consistent calculations of CD for steadystate scenarios j (MA/m 2 ) T e, T i (kev), n e (10 19 m 3 ) Total q 0.4 BS NB EC ρ n e T i 4 T e ρ q Example of FullCD I p =2.3MA B t =1.76T q 95 =5.4 f GW =0.85 f BS =0.65 β N =4.1 H H =1.3 I BS =1.49MA I NB =0.821MA I EC =0.015MA P PNB =20MW P NNB =10MW P EC =1.5MW
18 Summary advanced tokamak research Long pulse high β p Hmode  High integrated performance plasma with β N =2.6, H H98(y,2) ~1.0, f BS =0.4 was sustained for 25s (~14τ R ) by NTM avoidance NTM control  Importance of phasing was demonstrated  Modulated ECCD is >x2 superior to unmodulated ECCD RWM control  2 new instabilities at β N >β N : EWM & RWM precursor  β N >β N was sustained for 5s (~3τ R ) by RWM suppression JT60SA advanced tokamak research Design activity & physics assessment  Wide range of operational regime and plasma equilibrium  Full CD capability confirmed by simulation