Spherical Tokamak Plasma Science Comp-X General Atomics INEL - - PowerPoint PPT Presentation

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Martin Peng NSTX Program Director Oak Ridge National Laboratory @ Princeton Plasma Physics Laboratory

Joint Spherical Torus Workshop and US-Japan Exchange Meetings (STW2004) 29th September – 1st October, 2004 Kyoto University Yoshida-Honmachi, Kyoto, Japan

Spherical Tokamak Plasma Science & Fusion Energy Development

Supported by

Columbia U Comp-X General Atomics INEL Johns Hopkins U LANL LLNL Lodestar MIT Nova Photonics NYU ORNL PPPL PSI SNL UC Davis UC Irvine UCLA UCSD U Maryland U Rochester U Washington U Wisconsin Culham Sci Ctr Hiroshima U HIST Kyushu Tokai U Niigata U Tsukuba U U Tokyo JAERI Ioffe Inst TRINITI KBSI KAIST ENEA, Frascati CEA, Cadarache IPP, Jülich IPP, Garching U Quebec

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Spherical Tokamak (ST) Offers Rich Plasma Science Opportunities and High Fusion Energy Potential

• What is ST and why?
• Scientific opportunities of ST
• How does shape (κ, δ, A …) determine pressure?
• How does turbulence enhance transport?
• How do plasma particles and waves interact?
• How do hot plasmas interact with walls?
• How to supply magnetic flux without solenoid?
• Contributions to burning plasmas and ITER
• Cost-effective steps to fusion energy
• Collaboration

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Tokamak Theory in Early 1980’s Showed Maximum Stable βT Increased with Lowered Aspect Ratio (A)

• A. Sykes et al. (1983); F. Troyon et al. (1984) on maximum stable

toroidal beta βT:

βTmax = C Ip / a 〈B〉 ≈ 5 C κ / A qj; 〈B〉 ≈ BT at standard A

C ≈ constant (~ 3 %m·T/MA) ⇒ βN 〈B〉 = volume average B ⇒ BT κ = b/a = elongation A = R0/a = aspect ratio qI ≈ average safety factor Ip = toroidal plasma current BT ≈ applied toroidal field at R0

• Peng & Strickler (1986): What would happen to tokamak as A → 1?

− How would βN, κ, qj, change as functions of A?

Z a a b R R0

Plasma Cross Section

ST2004-9/29-10/1/04 ST Science & Fusion Energy

• Naturally increased κ ~ 2; ITF < Ip, IPF < Ip ⇒ higher Ip; lower device cost
• Increased Ip/aBT ~ 7 MA/m·T ⇒ βTmax ~ 20%, if βN ~ 3
• Increased Ip qedge /aBT ~ 20 MA/m·T ⇒

improved confinement?

ST Tokamak ITF / Ip (~aBT / Ip) ΣIPF / Ip κ

Natural Elongation, κ Small Coil Currents/Ip (qedge~2.5)

R R A Z

A = 2.5 κ ≈ 1.4 A = 1.5 κ ≈ 2.0

ST Plasma Elongates Naturally, Needs Less TF & PF Coil Currents, Increases Ip/aBT ⇒ Higher βTmax

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Very Low Aspect Ratio (A) Introduces New Opportunities to Broaden Toroidal Plasma Science

ST Plasmas Extends ST Plasmas Extends Toroidal Parameters Toroidal Parameters A = R/a can be ≥ 1.1

START – UKAEA Fusion

How does shape determine pressure?

• Strong plasma shaping & self fields

(vertical elongation ≤ 3, Bp/Bt ~ 1)

• Very high βT (~ 40%), βN & fBootstrap

How does turbulence enhance transport?

• Small plasma size relative to gyro-radius

(a/ρi~30–50)

• Large plasma flow (MA = Vrotation/VA ≤ 0.3)
• Large flow shearing rate (γExB ≤ 106/s)

How do plasma particles and waves interact?

• Supra-Alfvénic fast ions (Vfast/VA ~ 4–5)
• High dielectric constant (ε = ωpe

2/ωce 2 ~ 50)

How do plasmas interact with walls?

• Large mirror ratio in edge B field (fT → 1)
• Strong field line expansion

How to supply mag flux without solenoid?

• Small magnetic flux content (~ liR0Ip)

ST2004-9/29-10/1/04 ST Science & Fusion Energy

ST Research Is Growing Worldwide

HIST (J)

Globus-M CDX-U START TS-3,4 TST-M HIST, LATE Pegasus ETE

MAST NSTX

HIT-II Proto-Sphera SUNLIST Rotamak-ST HIT-I

TST-2 (J) TS-3 (J) TS-4 (J) Pegasus (US) CDX-U (US)

NSTX (US)

HIT-II (US)

MAST (UK)

ETE (B) SUNIST (PRC)

Proof of Principle (~MA) Concept Exploration (~0.3 MA)

Globus-M (RF)

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Pegasus Explores ST Regimes As Aspect Ratio → 1

ST2004-9/29-10/1/04 ST Science & Fusion Energy

NSTX Exceeded Standard Scaling & Reached Higher Ip/aBT, Indicating Better Field and Size Utilization

• Verified very high beta

prediction ⇒ new physics: βT = 2µ0〈p〉 / BT0

2 ≤ 38%

βN = βT / (Ip/aBT0) ≤ 6.4 〈β〉 = 2µ0〈p〉 / 〈B2〉 ≤ 20%

• Obtained nearly sustained

plasmas with neutral beam and bootstrap current alone

– Basis for neutral beam sustained ST CTF at Q~2 – Relevant to ITER hybrid mode

• ptimization
• To produce and study full non-

inductive sustained plasmas

– Relevant to DEMO

Columbia U, LANL, PPPL

CTF β requirement well within stability Limits, without using active control

CTF DEMO βN = 6

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Detailed Measurements of Plasma Profiles Allows Physics Analysis and Interpretations

Plasma Flow Shearing Rate up to ~106 /s

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Strong Plasma Flow (MA=Vφ/VAlfvén~0.3) Has Large Effects on Equilibrium and Stability

• Internal MHD modes

stops growing

• Pressure axis shifts
• ut by ~10% of outer

minor radius

• Density axis shifts by

~20%

0.4 0.6 0.8 1.0 1.2 1.4 R(m) 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

107540 330ms

MA Te(keV) ne (m-3) 4x1019 0.5 2.0 1.0 1.5

• 2
• 1

1 2 R(m) Z(m)

pressure surfaces magnetic surfaces Equilibrium Reconstruction with Flow

Columbia U, GA, PPPL, U Rochester

ST2004-9/29-10/1/04 ST Science & Fusion Energy

High-Resolution CHERS, SXR, and In-Vessel BR and BP Sensors Reveal Strong Mode-Rotation Interaction

CHarge-Exchange Recom- bination Spectroscopy (CHERS) shows vφ collapse preceding β collapse SXR shows rotating 1/1 mode during vφ decay

1/1 Island

In-vessel sensors measure rotating mode as vφ decays before mode locking

Aliased n=1 rotating mode

RWM, NTM, 1/1 modes, and rotation physics of high interest to ITER

Sabbagh, Bell, Menard, Stutman

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Active Control Will Enable Study of Wall Mode Interactions with Error Fields & Rotation at High βT

Columbia U, GA, PPPL

Resistive Wall Mode Growth Rate (s-1) Internal Sensors Conducting Plates Vacuum Vessel

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Global and Thermal τE’s Compare Favorably with Higher A Database

• TRANSP analysis for thermal

confinement

τE

<thermal> (ms)

τE

<ITER-H98p(y,2)> (ms)

120 80 40 120 80 40

0.00 0.01 0.02 0.03 0.04 0.05 0.00 0.05 0.10 τE<mag> [s] τE<ITER-97L> [s] H-mode L-mode x2.5 x1.5

• Compare with ITER scaling for total

confinement, including fast ions L-modes have higher non-thermal component and comparable τE! Why?

Bell, Kaye, PPPL

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Ion Internal Transport Barrier in Beam-Heated H-Mode Contrasts Improved Electron Confinement in L-Mode

Magnetic Axis

Kinetic Profile Local Error Sampling

Axis Edge

Regions requiring improved data resolution Transport Barrier region where χi ~ χi

NC

and χe >> χi

Columbia U, Culham, ORNL, PPPL

But L-mode plasmas show improved electron confinement! Why?

L-mode H-mode H-mode L-mode

Te (keV) ne (1013/cm3)

iITB? iITB?

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Transport Analysis of NSTX Plasmas Using TRANSP Confirms This Contrast

• χe >> χi ~ χNCLASS in most H-mode
• χe ~ χi in L-mode
• Diagnostic Resolution improvements continue

L-mode

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Analysis Shows Stability to Modes at Ion Gyro-Scale & Strong Instability at Electron Gyro-Scale (H-Mode)

Emissivity (mW/cm3) Ne 8,9+

MHD event Ne puff t ( m s ) R (cm)

• Driven by T and n

gradients

• kθρi < 1 (ion gyro-

scale) stable or suppressed by Vφ shear

• kθρi >> 1 (electron

gyro-scale) strongly unstable

Micro- instability calculations

• Dimp ~ Dneoclassical

Impurity Diffusivity

• χion ~ χneoclassical
• χelec >> χion

Thermal Conductivity In ion confinement zone Core Transport Physics

Cadarache, JHU, PPPL, U. Maryland

iITB?

ST2004-9/29-10/1/04 ST Science & Fusion Energy

A Broad Spectrum of Energetic Particle Driven Modes is Seen on NSTX

10 100 1000 0.1 0.2 0.3

TIME (s) FREQUENCY (kHz) “Fish-Bones” TAE CAE/GAE

108170

Do these Alfvén Eigenmodes (AEs) and fish-bones (f.b.s) Interact to expel energetic particles?

PPPL

ST2004-9/29-10/1/04 ST Science & Fusion Energy

TAE’s, “Fish-Bones,” and CAE/GAE’s Can Interact to Expel Energetic Particles

Synchronous sudden activities of

• Edge Dα rises; D-D neutron drops
• Fish-bone modes rises
• TAE mode crashes
• Separately, asynchronous drops of f.b.

and CAE modes

• So far observed for βT ≤ 10% and Ip ≤

700 kA ⇒ high-β effects?

• NPA measured depletion for 50-80 kV at

higher βT – MHD (m/n=4/2) induced?

• Nonlinear effects relevant to lower β

burning plasmas (ITER)

H-alpha (a.u.) Plasma Current (MW) Pnbi (MW) 0.8 0.4 0.0 1.0 0.0 1.0 0.0

shot 108530

4 0.2 0.3 0.0 0.1 0.4

TIME (s)

0.20 0.25 0.30 Neutrons (1014/s)

~ rms(B)

103 102 101 103 102 101 100 102 101 100 10-1 CAE 500 - 1500 kHz TAE 70 - 150 kHz f.b. 10- 40 kHz

(Ip = 0.65 MA, Pb = 3.6 MW, βT = 10%)

PPPL

ST2004-9/29-10/1/04 ST Science & Fusion Energy

NSTX RF Research Explores High Dielectric (ε ~ 100) Effects for Efficient Heating & Current Drive

• M. Ono (1995): High Harmonic

Fast Wave (HHFW) decay (absorption) rate: k⊥im ~ ne / B3 ~ ε / B, ε = ωpe

2 / ωce 2 ~ 102

Laqua et al (1997): Conversion

• f oblique O-mode to slow X-

mode to Electron Bernstein Wave (EBW):

Electromagnetic

Electrostatic Over-dense Plasma Launcher/ Receiver

&

ST2004-9/29-10/1/04 ST Science & Fusion Energy

HHFW: Heat Electrons and Trigger H-Modes, Relevant to Slowly Rotating ITER Plasmas

• Antenna operated in 6x(0-π) phasing for slow wave: kT ≈ 14m-1

0.5 0.0 1 2 3 50 0.0 0.1 0.2 0.3 0.0 0.1 0.2 0.3 0.4 0.5 Time [s] PHHFW [MW] WMHD, We [MJ] ne(0), <ne> [1020m-3] Ip [MA] Hα [arb] 0.5 1.0 1.5 Radius [m] 0.0 0.1 0.2 0.3 0.4 1 ne [1020m-3] Te [keV]

0.243s 0.293s 0.343s 0.393s 0.243s 0.293s 0.343s 0.393s

LeBlanc

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Frequency = 14 GHz

Electron Bernstein Wave: Oblique "O-X-B" Launch Is Resilient to Changes in Edge Density Gradient

• Optimum n// = 0.55;

toroidal angle ~ 34o from normal to B

• > 75% coupling for O-

X-B antenna with ± 5 degree beam spread

EBW Coupling (%) 80 60 40 20

OPTIPOL/GLOSI

Efficient conversion between ECW and EBW predicted.

ST2004-9/29-10/1/04 ST Science & Fusion Energy

EBW Emission Shows Near-Circular Polarization and Trad/Te ~ 70%, Consistent with Modeling

0.4 1.6 1.2 0.8 1.0 2.0 Thomson Scattering Te (keV) Total EBW Trad (keV)

(Including Window/Lens Loss)

Ratio of Radiometer Signals Time (s) Field Pitch (Deg.) 10 40 Magnetic Field Pitch 35-40 Degrees

Frequency = 16.5 GHz

OPTIPOL/GLOSI

Poloidal Angle (deg.) Toroidal Angle (deg.)

• 90

90

• 90

90

> 90% EBW Coupling

B

10% 10%

• Approx. Antenna Acceptance Angle

Average Coupling ~ 70%

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Bt = 3.75 kG b = 42%

28 GHz

Modeling Predicts that 28 GHz EBW Can Drive Efficient Off-Axis Current at Plasma β ~ 40%

• EBW ray tracing, deposition and CD efficiency being studied with

GENRAY & CQL3D for frequencies between 14 to 28 GHz

GENRAY/CQL3D [Bob Harvey, CompX]

Frequency = 28 GHz EBW Power = 3 MW Total Driven Current = 135 kA 30 15 0.2 0.8 0.6 0.4

1.5 Z(m)

• 1.5

R(m)1.4 0.4 Antenna

r/a

Current Density (A/cm2)

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Strong Diffusion Near Trapped-Passing Boundary Enables Efficient Ohkawa Current Drive

CompX GENRAY/CQL3D

NSTX, βT = 42%

ST2004-9/29-10/1/04 ST Science & Fusion Energy

ST Plasma Edge Possesses Large Mirror Ratio & Geometric Expansion of Scrape-Off Layer (SOL)

10 20 30 1.55 1. 6 1. 6 5 1. 7

R (m) in SOL

A B

Area Expansion Ratio Larger Geometric Expansion

0.50 0.75 1.00 2 4 6 8

Distance Along SOL Field Line (m)

inboard

• utboard

|B| (T) Larger Mirror Ratio (MR) → More Instabilities → Larger ⊥ Loss → Thicker SOL

Scrape-Off Layer Geometry

• f Inboard Limited ST Plasma

0.25 0.5 0.75 1 1.25 1.5

• 1
• 0.5

0.5 1 1.5

R(m) Z(m)

A Plasma Flux to Limiter Divertor Limiter SOL Flux Surface Plasma Edge B: Plasma Flux To Divertor

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Increased SOL Mirror Ratio (MR) ⇒ Increased Footprint & Decreased Peak of Divertor Heat Flux

High & Low δ Divertor Bolometer Measurements Rdiv (m) 0.36 0.75 SOL MR ~ 3 ~ 1.5 ∆div (m) ~ 0.3 ~ 0.12

Factor of ~2 in Rdiv and MR ⇓ Factor of ~3 in ∆div Why?

SOL MR ≈ 3 SOL MR ≈ 1.5

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Plasma Edge Studies Reveal Turbulence and “Blobs” Important to Divertor Flux Scaling Studies

He manifold Side-viewing reentrant window

H-mode

L-mode

Broadly Based Study:

• Gas Puff Imaging

views along field lines (PPPL, LANL)

• Very fast camera,

105/s (PSI)

• Reflectometers and

edge (UCLA, ORNL)

• Reciprocating probe

(UCSD)

• Divertor fast camera

(Hiroshima U)

• IR Cameras (ORNL),

Filterscope (PPPL)

• Modeling (PPPL,

UCSD, LLNL, Lodestar)

105710

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Tray after ~40 discharges. Liquid lithium tray limiter in CDX-U

CDX-U Is Testing Innovative Lithium Plasma Facing Component Effects, to Control Recycling

• First successful test of toroidal liquid lithium tray limiter
• Dramatic reduction in plasma edge fuel recycling, lowering impurity

influx and loop voltage

• NSTX tests of lithium pellets and lithium wall coating in 2004

PPPL, UCSD, ORNL, SNL

ST2004-9/29-10/1/04 ST Science & Fusion Energy

CHI + OH OH only HIT-II Experiment

Culham, KAIST, Kyushu-Tokai U, PPPL, U Tokyo, U Washington

New absorber insulator installed Capacitor bank to be installed

Three Outer Poloidal Field Startup Scenarios, e.g.: Outboard Field Null Flux contours 20 kA

• 20 kA

2.8 kA Coaxial Helicity Injection Tests

Solenoid Free Start-Up via Coaxial Helicity Injection & Outer Poloidal Field Coil Are Being Tested

ST2004-9/29-10/1/04 ST Science & Fusion Energy

JT-60U Tests on Solenoid-Free Start-Up via RF and NBI Offers Additional Exciting Opportunities

Startup RF + NBI RF Ramp-up

• U. Tokyo, JT-60U – JAERI
• JT-60U: from 200

kA to 700 kA with LHW + NBI (2002)

• PLT: 100 kA with

LHW (1980s)

• CDX-U, TST-2: up

to 4 kA with ECH

• MAST: 1-MW ECH
• NSTX: to develop

and test up to 4- MW EBW in 5 years

• Utilize outer PF coil

induction with simple ramp

ST2004-9/29-10/1/04 ST Science & Fusion Energy

High βT High τE

Co-NBI plasmas:

• Improved vertical

control ⇒ higher κ

• βp t 1 and IBS/Ip d 0.5
• βN ~ 6 and βT > 20%
• Reduced VL
• Help developing

ITER hybrid scenario

• Driven steady state

ST plasmas (CTF).

• Need to reduce ELM

size

Nearly Sustained Plasmas with Broader Values of κ, li, Ip, and βT Can Contribute to ITER Hybrid Scenario

ST2004-9/29-10/1/04 ST Science & Fusion Energy

NSTX Made Large Progress in Producing and Studying the Science of Attractive Sustained Plasmas

FY01-03

• EFIT02
• Peak βT
• All shapes

NSTX Potential

FY04 Fraction of Self-Driven Current fBS ~ 0.5 × ε½βP

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Long-Pulse H-Mode Plasmas Made Large Progress in Physics Basis for Next-Term ST Science Facilities

Well positioned to address the science of sustained high-performance plasmas.

ARIES-AT (4MW/m2) CTF-ST

}

τpulse/τE Normalized pulse length

Normalized beta x normalized confinement NSTX Operation

ARIES-ST (4WM/m2) 4 2 1 MW/m2

NSST

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Research Topics to Achieve Long-Pulse, High Performance Plasmas Are Identified

• Enhanced shaping

improves ballooning stability

• Mode, rotation, and error

field control ensures high beta

• NBI and bootstrap sustain

most of current

• HHFW heating may

contribute to bootstrap

• EBW provides off-axis

current & stabilizes tearing modes

• Particle and wall control

maintains proper density

CompX, MIT, PPPL, ORNL, UCSD

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Answering the Plasma Science Questions Also Enable Cost-Effective Steps toward Fusion Energy

Smaller unit size for sustained fusion burn ⇒ How does turbulence enhance transport? Efficient fusion α particle, neutral beam, & RF heating ⇒ How does plasma particles and waves interact? Simplified smaller design, reduced operating cost ⇒ How to supply magnetic flux without solenoid? Lowered magnetic field and device costs ⇒ How does shape determine pressure? Survivable plasma facing components ⇒ How do hot plasmas interact with wall? Optimize Fusion DEMO & Development Steps ⇒ Plasma Science Questions in Extended ST Parameter Space

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Future ST Steps Are Estimated to Require Moderate Sizes to Make Key Advances toward DEMO

60 30 ~15 ~0.01 ~0.01 Duty factor (%) ~2.1 ~12 ~4 ~300 ~50 ~5 ~2.6 ~10 0.3 1 5 Single-turn; No-solen. Single-turn; No-solen. Multi-turn; Solenoid Multi-turn; Solenoid TFC; Solenoid ~4 ~1 − − WL (MW/m2) ~3100 ~77 ~10 − Pfusion (MW) Steady state Steady state ~50 1 Pulse (s) ~1.8 ~1.1 0.6 BT (T) ~25 ~9 ~5 1.5 Ip (MA) ~3.2, ~0.5 ~3, ~0.5 ~2.7, ~0.7 2.5, 0.8 κ, δ ~2 ~0.8 ~0.9 0.65 a (m) ~3 ~1.2 ~1.5 0.85 R (m) Practicality of Fusion Electricity Energy Development, Component Testing Performance Extension Proof of Principle Mission DEMO CTF NSST NSTX Device

ST2004-9/29-10/1/04 ST Science & Fusion Energy

ST Research Has Broad and Growing Opportunities for Collaborations

• Exploratory ST’s in Japan

– TST-2: ECW-EBW initiation – TS-3,4: FRC-like β~1 ST plasmas – HIST: helicity injection physics – LATE: solenoid-free physics

• Active participation in ITPA (ITER)

– A and β effects on confinement, ITB, ELM’s, pedestal, SOL, RWM, and NTM; scenarios, window coating, etc.

• ST Database with MAST, U.K.

– NBI H-mode, transport, τE – EBW H&CD (1 MW, 60 GHz), FY03 – Divertor heat flux studies, FY03-04 – NTM, ELM characterization

• DIII-D & C-Mod collaboration

– Joint experiments: RWM, Fast ion MHD, pedestal, confinement, edge turbulence, X-ray crystal spectrometer

• MST: electromagnetic turbulence, EBW

C-Mod (U.S.) DIII-D (U.S.) MST (U.S.) MAST (U.K.)

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Spherical Tokamak (ST) Offers Rich Plasma Science Opportunities and High Fusion Energy Potential

• Early MHD theory suggested ST could permit high β,

confirmed recently by experiments

• Recent research identified new opportunities for

addressing key plasma science issues using ST

• Results have been very encouraging in many scientific

topical areas

• ST research contributes to burning plasma physics
• ptimization for ITER
• ST enables cost-effective steps toward practical

fusion energy

• ST research is highly collaborative worldwide

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Backup VUs

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Minimizing Tokamak Aspect Ratio Maximizes Field Line Length in Good Curvature ⇒ High β Stability

Tokamak Compact Toroid (CT) Spherical Tokamak (ST)

Bad Curvature Good Curvature Magnetic Field Line Magnetic Surface

Small-R close to Tokamak & large-R close to CT.

ST2004-9/29-10/1/04 ST Science & Fusion Energy

ST Is Closest to Tokamak; Operates with High Safety Factor and More Comparable Self & Applied Fields

Field Reversed Configuration Reversed Field Pinch Dipole Spheromak

Improve Plasma Stability at High β → Average Safety factor, qavg 5

Example Example Fusion Configurations Fusion Configurations

Spherical Tokamak (Spherical Torus) (NSTX, MAST, TST-2, TS-3,4, HIST, LATE, etc.) Tokamak & Advanced Tokamak (DIII-D, C-Mod, K-Star, JT60-U, etc.) Stellarators (QPS) In Design (NCSX) Being Built

0.5

(Applied Field)/(Applied + Plasma-Produced Field)

1

(Self-Organized) Increase Controllability → (Externally Controlled) (LDX, etc.) (SSPX, etc.) (MST, etc.) (LDX, etc.)

LHD

ST2004-9/29-10/1/04 ST Science & Fusion Energy

In MAST, However, Counter NBI Reduces Electron Energy Loss

High flow shear scenario on MAST (Co- & Counter-NBI)

• Counter-NBI produces stronger

ωSE ~ 106 s-1 and strong local reduction in χe at broader radius

• Pressure gradient contribution to

Er reinforces that due to Vφ with ctr-NBI

• Strong ExB flow shear and weak

magnetic shear s ~ 0 produced by NBI heating during current ramp

• With co-NBI ion thermal transport

reduced to N.C. level χi ~ χi

NC

with weaker reduction in χe

• Strong ExB flow shear ωSE >

γm

ITG and s ~ 0 at minimum of χi,e

0.0 0.2 0.4 0.6 0.8 1.0 3 4 5 2 1 0.0 1.5 1.0 0.5

ρ [keV] ne Ti Te

.2 s 0.0 0.2 0.4 0.6 0.8 1.0 3 4 5 2 1 0.0 1.5 1.0 0.5

ρ [1019 m-3]

#8302, 0.2 s 0.0 0.2 0.4 0.6 0.8 1.0

ρ [m2 s-1]

8575, 0.2 s 1.0 100 10 0.1

χi χe

NC

0.0 0.2 0.4 0.6 0.8 1.0

ρ

#8302, 0.2 s 1.0 100 10 0.1 #8

χφ χi

N

#830

Co-NBI Counter-NBI

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Detailed Diagnosis and Gyrokinetic Analysis of β ~ 1 Turbulence Has Broad Scientific Importance

Can k¦ρι ≥ 1 turbulence at β ~ 1 be understood?

Region to be tested Armitage (U. Colorado)

• Astrophysics turbulence dynamics: cascading of MHD turbulence to ion

scales is of fundamental importance at β > 1

• Fusion’s gyrokinetic formalism apply to astrophysical turbulence, covering

shocks, solar wind, accretion disks

• Laboratory ST plasmas provide validation of formulism

Gyrokinetic turbulence simulation in accretion disk of supermassive black hole at galactic center, assuming damping of turbulence by plasma ions vs. electrons

ST2004-9/29-10/1/04 ST Science & Fusion Energy

Single-turn demountable center leg

for toroidal field coil required to achieve small size and simplified design.

Fast remote replacement of all fusion

nuclear test components (blanket, FW, PFC) & center post required to permit high duty factor & neutron fluence.

Large blanket test areas ∝ (R+a)κa.

Adequate tritium breeding ratio &

small fusion power from low A required for long term fuel sufficiency.

High heat fluxes on PFC. Initial core components could use

DEMO-relevant technologies (such as from ITER and long-pulse tokamaks).

12-MA power supply – Single-turn TF.

Features Required by High Duty Factor & Neutron Fluence

Optimized Device Configuration Features of ST Can Fulfill the CTF Mission Effectively