Introduction to Spherical Tokamak SUNIST or 4th Workshop on Nonlinear Plasma Sciences International School on Plasma Turbulence and Tran Hangzhou 2005 GAO, Zhe Department of Engineering Physics Tsinghua University, Beijing 100084 [email protected]
Jan 23, 2016
Introduction to Spherical Tokamak
SUNISTSUNIST
for 4th Workshop on Nonlinear Plasma Sciences & International School on Plasma Turbulence and Transport
Hangzhou 2005
GAO, ZheDepartment of Engineering PhysicsTsinghua University, Beijing [email protected]
OUTLINE
• What is the spherical tokamak?
• ST advantage
• ST worldwide
• New physics of toroidal plasmas
• Potential contribution
• What is the Spherical Tokamak?
Spherical tokamak
Spherical torus tokamak
Spherical tokamak=low aspect ratio tokamak
Aspect ratio, A=R/a
ST in Fusion configuration family
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The first ST: START
• AdvantageCompact configuration
Natural elongation
Large qa n r si c ea e t n y o toro l l (he efficie c f ida fie d
ypyyrod yy>
large plasma current
lower toroidal field (paramagnetism)
High β
High density limit
Less major disruption (instead of IREs)
Good energy confinement
Improved confinement mode achieved
• ST worldwide
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Parameters achieved
MAST NSTX
major radius R (m) 0.7 0.85
minor radius a (m) 0.5 0.68
elonggation κ 2.45 2.2
aspect ratio A (R/a) 1.3 1.27
plasma current IP (MA) 1.35 1.5
toroidal field BT(R0) (T) 0.52 0.6
neutral beam power PNBI (MW) 3.3 7
RF power P (MW) 1.5 ECRH HHFW 6
pulse length (s) 0.7 1.1
• Extended toroidal plasmas & New Physics(1) elongation>3, Bp/Bt~1, β~40%, Vrotation/Valfven~0.3
High βy l r r rot t ony stron s p qu la ge a i g ha ed e i
r umib i
(2) High β, low Valfven,, strong shear γE*B~106/s
yl trom n t tur ul n n ec ag e ic b e ce a dtr nporta t low ya
(3) a/ρi~30-50, a/ρfast ion~3-10, near omnigeneity, strongly mag well
Neoclassical transport at low A
(4) Valfven ~ Vs, Vfast ion>>Valfven ,less damping on TAE
st on p ys sFa i h ic
(5) High dielectric constant (ωpe2/ ωce
2~50-100)
y v yp rt l nt r t on (R t n a e a ic e i e ac i F hea i gyy yD
(6) Narrow inner regions and Low li yol no y r st rtupe idfe e a
Topical Research Plan of ST ( NSTX Five Year Plan)• MHD: RWM active and passive stabilzation
Fast-ion MHD (Alfven like)
NTM (stabilization by RF)
High beta equilibrium
• Transport and turbulence: high k and low k turbulence
H mode
Electron thermal barriers
Aspect ratio scaling
• Wave-plasma interaction: HHFW, EBW
• Solenoid-free startup: Transient CHI, PF induction, RF(ECH/EBW)
• Boundary Physics: Li conditioning, SOL transport
• Integration
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• What might ST bring to fusion application ?
Contribute to AT & burning plasma (ITER) physics
• Advanced Tokamak concept
High plasma kinetic pressure
Good confinement
High self-sustained current
(Quasi-) Stationary state
Advance fuel recycle
• Burning plasma
Other application:
VNSCTFContribution to AT and burning plasma researchSpace propulsion
Future Steps
Tokamak
* T-3, T-4, ST etc. 1970’s
** PLT, ASDEX etc.later 70’s
***TFTR,JET, JT-60U, 80—90‘s
**** ITER
2100’s
SUNIST: Sino United Spherical Tokamak
major radius R 0.3m
minor radius a 0.23m
Aspect ratio A ~1.3
elongation κ ~1.6
toroidal field ( R0) BT 0.15T
plasma current IP 50kA
central rod current IROD 0.225MA
flux (double swing) ΔΦ 0.06Vs
• AcknowledgementCollecting material from the following references:
Peng Y-K, STW2004, Kyoto.
Gryaznevich M, STW2004, Kyoto.
Peng Y-K, STW2003, Culham.
Peng Y-K, Phys. Plasmas 2000, 7(5): 1681.
Sykes A, Nucl. Fusion 1999, 39(9Y):1271.
NSTX team, NSTX five year research plan
Peng Y-K and Strikler DJ, Nucl. Fusion 1986, 26:576
and many ST Websites.
TOKAMAK
Spheromak
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ST: more compact
ST: natural elongation
ST: High qa
ST: high beta
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ST: high density
ST: more stable for VDI Internal Reconnection Event (IRE)
• ST: good confinement
High beta equilibrium with larger rotation
turbulence and transport
Single particle motion in ST
HHFW CD
EBW CD
Diffusion near the T-P boundary
CHI startup
Outer Poloidal Field startup
• ECH startup
• Bootstrap current MAST (real discharge) NSTX (Theo prediction)
• Divertor configuration
Divertor configurations in MAST:
Double-Null Divertor (DND)
Limited, or Natural Divertor (ND)
Single-Null Divertor(SND)
H-mode in DND and Natural Divertor plasmas