US-Japan Workshop on MHD Control, Magnetic Islands and Rotation the University of Texas, Austin, Texas, USA AT&T Executive Education & Conference Center NOVEMBER 3-5, 8 MHD Stabilization Analysis in Tokamak with Helical Field Kozo Yamazaki Nagoya University
INTRODUCTION Our aim is to search for a Compact & Disruption-Free Configuration. () COMPACT => Low Aspect Ratio? Advanced Shaping? () DISRUPTION-FREE => Helical system? Tokamak Stellarator Hybrid?
() COMPACT? N= N= Advanced Plasma Shaping Smaller N N= N=3 N=4 N=5 QA Quasi Axi Symmetry QP Quasi Poloidal Symmetry QO Quasi Omunigenity Tokamak N= proposal CHSqa QPS NCSX QH Quasi Helical Symmetry Core Symmetry Modular Coil Surface Symmetry Helical Divertor Continuous Coil N=, proposal N/L=4/ N/L=/ 3
NEW Proposal Ballooning Beta Limit of QI Configurations N= A~3.9, <β>=.4% N=3 A~6.8, <β>=3.9% N=4 A~9 <β>=5% N=6 A~ <β>=5~8.8% N=9 A~ <β>=~5% By adding plasma current, we may get higher beta. It is not easy to find out a compact good-confinement and high beta configuration. M.Mikhailov & K.Yamazaki 4
Exotic Tokamak-Stellarator Hybrids Ikuta Torus (K.Ikuta, 968) Cleftron (T.Ohkawa, 98) Ultra Simple Stellarator (T.Todd,99) CNT (T.S.Pedersen & A.H.Boozer, ) Non-Axisymmetric Shaping Proposals C-Tokastar (K.Yamazaki,4) Strong Negative V (H.P.Furth et al., 968) Tokatron (H.P.Furth et al., 98) Tokastar (K.Yamazaki, 985) Spherical Stellarator (P.E.Moroz, 996) 5
() DISRUPTION-FREE? Disruption-Free in Helical System no disruption with q(external)<7 even at q~ W7-A JIPP T-II WVII- A Team, Nucl. Fusion (98) 93. Fujita et al., IEEE Transaction on Plasma Science PS-9 (98) 8. (Current Carrying Stellarator without BS current)
() COMPACT () DISRUPTION-FREE Can external helical filed play a role in tokamak? (TM,NTM,RWM, Ballooning mode etc.) Integrated Simulation Studies (TOTAL code) Small Plasma Experiment (Tokastar) Reactor Assessment (COE,CO, EPR etc.) K.Yamazaki et al. IAEA 8 7
TOTAL Code Development For Predictive Simulation and Experimental Data Analysis TOTAL-H TOTAL-T <Helical> Magnetic Field Tracing (HSD,MAGN) <Tokamak> -D Equilibrium (APOLLO) Toroidal Transport Analysis Linkage 3-D Equilibrium (VMEC) Boozer Coordinates Mercier Mode Flux Coordinates Ballooning Mode NBI Deposition (HFREYA,NFREYA) Bootstrap Current NeoclassicalTransport (GIOTA, NCLASS) GLF3 -D Transport (HTRANS) NTM Analysis Fast Ion FokkerPlank Eq. (FIFPC) Neutral Transport (AURORA) Impurity Radiation (IMPDYN) Pellet Injection 8
dw dt Γ = Γ Γ Γ Γ BS GGJ pol EC k NTM with Helical Field Model: Modified Rutherford Equation = Γ + Γ + Γ + Γ + Γ + Γ BS η ( W ) µ = k 4 = k ηl = k 3 q j η µ η µ BS Lq = k5η ρ GGJ s ε g s ρ B β ( ε, ν ) s B ps p p ρ ρ W L q ρ L i pol s β ps fη p EC W + W I EC d q ρ pil Lp EC a q s W HF ρ ρ W W 3 +.W d Resonant HF Γ m W ( HF ) HF = χ 4 χ br 4 cosφ W d ( ) ( + ) r W χ χ 4 s Non-resonant HF Q.Yu et al., PRL 85()949 9
Example of NTM analysis of an ITER Plasma without external helical field T e [kev] 3 5 5 5 3/ mode no NTM / mode 3/ + / mode..4.6.8 ρ 3/ island / island 3.5 3.5.5 q W.5..5..5 ECCD 3 35 4 45 5 55 6 65 time [s] / mode 6[kA] 8[kA] [ka] [ka]
Non-Resonant Helical Field Application Stabilized.3.3 [s - ].. -E-6 -. -. BS dw/dt GGJ [s - ].. -. -. GGJ BS dw/dt -.3 -.3.5..5. w/a.5..5. w/a Without Helical Field With Helical Field B r /B ~ -3
Experimental Preparation () C-Tokastar magnetic surface # magnetic surface #.5 -.5 -.5 -.5 - -.5 - -.5.5.5 -.5 - -.5.5.5 magnetic surface #3 magnetic surface #4.5 -.5 -.5 -.5 - -.5 - -.5.5.5 -.5 - -.5.5.5 Vacuum magnetic field in N= C-Tokastar with double helical coil. Finite beta equilibrium
R coil= 6cm B <. kg Now checking magnetic surfaces using impedance method 3
() Tokastar- under construction N= outer helical field coils are installed outside toroidal field coil. Vacuum magnetic surfaces exist as a pure stellarator operation. 4
R ~ cm a~ 5 cm B ~ kg Ip < ka P ECH ~ kw All were installed in the vacuum chamber, and now in baking process 5
Summary () ().5-D(dimensional) tokamak code and.-d helical code have been developed and, preliminary analysis for TM, NTM in Tokamak with helical field has been started. Small Tokamak-Stellarator Hybrids, C-Tokastar and Tokastar- are under construction. The experiments on resonant or non-resonant magnetic field application to tokamak will be started in the near future. 6