Supported by
Columbia U Comp-X General Atomics Spherical Tokamak Plasma Science INEL Johns Hopkins U LANL LLNL & Fusion Energy Development Lodestar MIT Nova Photonics NYU ORNL PPPL PSI SNL Martin Peng UC Davis UC Irvine NSTX Program Director UCLA UCSD U Maryland Oak Ridge National Laboratory U Rochester U Washington @ Princeton Plasma Physics Laboratory U Wisconsin Culham Sci Ctr Hiroshima U HIST Kyushu Tokai U Niigata U Joint Spherical Torus Workshop and Tsukuba U U Tokyo US-Japan Exchange Meetings (STW2004) JAERI Ioffe Inst TRINITI KBSI th st KAIST 29 September – 1 October, 2004 ENEA, Frascati CEA, Cadarache Kyoto University IPP, Jülich IPP, Garching Yoshida-Honmachi, Kyoto, Japan 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 Z Plasma 〈B〉 = volume average B ⇒ B Cross T Section κ = b/a = elongation b A = R /a = aspect ratio a a 0 0 R R qI ≈ average safety factor 0
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?
ST2004-9/29-10/1/04 ST Science & Fusion Energy ST Plasma Elongates Naturally, Needs Less TF & PF
Coil Currents, Increases Ip/aBT ⇒ Higher βTmax
Natural Elongation, κ Small Coil Currents/Ip (qedge~2.5)
A = 1.5 A = 2.5 ITF / Ip κ≈2.0 κ≈1.4 (~aBT / Ip)
Z ΣIPF / Ip
κ
0 RRST ATokamak
• 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? ST2004-9/29-10/1/04 ST Science & Fusion Energy Very Low Aspect Ratio (A) Introduces New Opportunities to Broaden Toroidal Plasma Science
How does shape determine pressure? ST Plasmas Extends • Strong plasma shaping & self fields
Toroidal Parameters (vertical elongation ≤ 3, Bp/Bt ~ 1)
• Very high βT (~ 40%), βN & fBootstrap A = R/a can be ≥ 1.1 How does turbulence enhance transport? • Small plasma size relative to gyro-radius
(a/ρi~30–50)
• Large plasma flow (MA = Vrotation/VA ≤ 0.3) 6 • Large flow shearing rate (γExB ≤ 10 /s) How do plasma particles and waves interact?
• Supra-Alfvénic fast ions (Vfast/VA ~ 4–5) 2 2 • High dielectric constant (ε = ωpe /ωce ~ 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? START – UKAEA Fusion • Small magnetic flux content (~ liR0Ip) ST2004-9/29-10/1/04 ST Science & Fusion Energy ST Research Is Growing Worldwide
Concept Exploration (~0.3 MA) Proof of Principle (~MA)
HIT-II (US) Pegasus (US) MAST (UK)
Globus-M NSTX (US) Pegasus MAST HIT-II START Proto-Sphera TS-3,4 HIT-I NSTX SUNLIST TST-M CDX-U HIST, LATE
ETE Rotamak-ST
CDX-U (US) Globus-M (RF)
ETE (B)
SUNIST (PRC) HIST (J) TST-2 (J) TS-4 (J) TS-3 (J) 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
CTF β requirement well within stability • Verified very high beta Limits, without using active control prediction ⇒ new physics: 2 βT =2µ0〈p〉 /BT0 ≤ 38%
DEMO βN = βT / (Ip/aBT0) ≤ 6.4 β = 6 N 2 〈β〉 = 2µ0〈p〉 / 〈B 〉≤20% • Obtained nearly sustained plasmas with neutral beam CTF and bootstrap current alone – Basis for neutral beam sustained ST CTF at Q~2 – Relevant to ITER hybrid mode optimization • To produce and study full non- inductive sustained plasmas – Relevant to DEMO
ST2004-9/29-10/1/04 Columbia U, LANL, PPPL 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
Equilibrium Reconstruction • Internal MHD modes with Flow stops growing pressure surfaces 2 • Pressure axis shifts magnetic surfaces out by ~10% of outer minor radius • Density axis shifts by 1 ~20%
107540 1.4 T (keV) 0 e 330ms Z(m) 1.2
1.0
0.8 -3 -1 0.6 ne (m ) 19 0.4 4x10 MA 0.2 0.0 0.4 0.6 0.8 1.0 1.2 1.4 -2 R(m) 0.51.0 1.5 2.0 Columbia U, GA, PPPL, U Rochester R(m) 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
In-vessel sensors measure SXR shows rotating 1/1 rotating mode as vφ decays mode during v decay CHarge-Exchange Recom- before mode locking φ bination Spectroscopy
(CHERS) shows vφ collapse preceding β collapse Aliased n=1 rotating mode
1/1 Island
Sabbagh, Bell, Menard, Stutman RWM, NTM, 1/1 modes, and rotation physics of high interest to ITER 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 ) -1
Vacuum Vessel Conducting Plates Resistive Wall Mode GrowthResistive Wall Mode (s Rate
Internal Sensors Columbia U, GA, PPPL ST2004-9/29-10/1/04 ST Science & Fusion Energy Global and Thermal τE’s Compare Favorably with Higher A Database
0.10 120 H-mode .5 L-mode 2 x
.5 80 x1 (ms) [s] 0.05
0.00 0 0.00 0.01 0.02 0.03 0.04 0.05 0 40 80 120 τ
L-modes have higher non-thermal component and comparable τE! Why?
ST2004-9/29-10/1/04 Bell, Kaye, PPPL ST Science & Fusion Energy Ion Internal Transport Barrier in Beam-Heated H-Mode Contrasts Improved Electron Confinement in L-Mode
iITB? Transport Kinetic Profile Local Error Sampling Barrier region where NC χi ~ χi Regions requiring and improved χe >> χi data resolution iITB?
Axis Edge But L-mode plasmas show improved electron confinement! Why? )
L-mode 3 H-mode /cm
13 L-mode (keV)
Magnetic Axis e H-mode (10 T e n
ST2004-9/29-10/1/04 Columbia U, Culham, ORNL, PPPL 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) ) 3 Core Transport In ion confinement MHD event Physics zone Ne 8,9+ Thermal • χion ~ χneoclassical
Conductivity • χelec >> χion
Impurity •D ~ D Emissivity (mW/cm imp neoclassical R ( Diffusivity cm ) ) t (ms • Driven by T and n Micro- uff Ne p instability gradients iITB?
calculations •kθρi < 1 (ion gyro- scale) stable or
suppressed by Vφ shear
•kθρi >> 1 (electron gyro-scale) strongly unstable
ST2004-9/29-10/1/04 Cadarache, JHU, PPPL, U. Maryland ST Science & Fusion Energy A Broad Spectrum of Energetic Particle Driven Modes is Seen on NSTX
Do these Alfvén Eigenmodes (AEs) and fish-bones (f.b.s) Interact to expel energetic particles?
108170
1000 CAE/GAE
TAE
100
FREQUENCY (kHz) FREQUENCY “Fish-Bones”
10 0.1 0.2 0.3
PPPL ST2004-9/29-10/1/04 TIME (s) ST Science & Fusion Energy shot 108530 0.8 Plasma TAE’s, “Fish-Bones,” and Current (MW) 0.4 4 CAE/GAE’s Can Interact to Pnbi (MW) 0.0 0 0.0 0.10.2 0.3 0.4 Expel Energetic Particles
1.0 H-alpha (a.u.)
(Ip = 0.65 MA, Pb = 3.6 MW, βT = 10%)
0.0 1.0 Synchronous sudden activities of Neutrons (1014/s) • Edge Dα rises; D-D neutron drops • Fish-bone modes rises 0.0 f.b. 10- 40 kHz 103 • TAE mode crashes 102 • Separately, asynchronous drops of f.b. 101 and CAE modes 102 • So far observed for β ≤ 10% and I ≤ ~ 101 T p 700 kA ⇒ high-β effects? 100 CAE 500 - 1500 kHz rms(B) 10-1 • NPA measured depletion for 50-80 kV at 103 higher β – MHD (m/n=4/2) induced? 102 T
101 • Nonlinear effects relevant to lower β TAE 70 - 150 kHz 100 burning plasmas (ITER) 0.20 0.25 0.30 TIME (s) 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 Laqua et al (1997): Conversion (absorption) rate: of oblique O-mode to slow X- 3 k⊥im ~ ne / B ~ ε / B, mode to Electron Bernstein 2 2 2 ε = ωpe / ωce ~ 10 Wave (EBW): & Electrostatic
Launcher/ Over-dense Receiver Plasma Electromagnetic
ST2004-9/29-10/1/04 ST Science & Fusion Energy HHFW: Heat Electrons and Trigger H-Modes, Relevant to Slowly Rotating ITER Plasmas
Ip [MA] Te [keV] 0.293s 0.5 H [arb] α 1 0.343s 0.0 3 PHHFW [MW] 0.393s
2 0.243s 1 0 0 n [1020m-3] WMHD, We [MJ] e 50 0.4 0.393s
0.3 0.343s 0 n (0),
0.2 0.1 0.1 0.243s 0.0 0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.5 1.0 1.5 Time [s] Radius [m] LeBlanc -1 • Antenna operated in 6x(0-π) phasing for slow wave: kT ≈ 14m ST2004-9/29-10/1/04 ST Science & Fusion Energy Electron Bernstein Wave: Oblique "O-X-B" Launch Is Resilient to Changes in Edge Density Gradient
Efficient conversion between ECW and EBW predicted.
Frequency = 14 GHz
• 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
ST2004-9/29-10/1/04 ST Science & Fusion Energy EBW Emission Shows Near-Circular Polarization and
Trad/Te ~ 70%, Consistent with Modeling
Approx. Antenna Acceptance Angle Average Coupling ~ 70% Magnetic Field Pitch 35-40 Degrees 1.6 OPTIPOL/GLOSI 90 Total 1.2 Thomson EBW Scattering T (keV) Te (keV) 10% B rad 0.8 (Including Window/Lens 0.4 Loss) 10% 0 2.0 0 Ratio of Radiometer 1.0 Signals Poloidal Angle (deg.)
> 90% EBW Coupling 40 -90 Field -900 90 Pitch Toroidal Angle (deg.) (Deg.) 10 Frequency = 16.5 GHz Time (s)
ST2004-9/29-10/1/04 ST Science & Fusion Energy Modeling Predicts that 28 GHz EBW Can Drive Efficient Off-Axis Current at Plasma β ~ 40%
Frequency = 28 GHz EBW Power = 3 MW Total Driven Current = 135 kA
28 GHz 1.5 30
Z(m) 15 Antenna
Bt = 3.75 kG (A/cm2) Current Density -1.5 0.4 1.4 b = 42% R(m) 0 0.2 0.4 0.6 0.8 r/a • EBW ray tracing, deposition and CD efficiency being studied with GENRAY & CQL3D for frequencies between 14 to 28 GHz
GENRAY/CQL3D [Bob Harvey, CompX] ST2004-9/29-10/1/04 ST Science & Fusion Energy Strong Diffusion Near Trapped-Passing Boundary Enables Efficient Ohkawa Current Drive
NSTX, βT = 42%
CompX GENRAY/CQL3D ST2004-9/29-10/1/04 ST Science & Fusion Energy ST Plasma Edge Possesses Large Mirror Ratio & Geometric Expansion of Scrape-Off Layer (SOL)
Scrape-Off Layer Geometry 1.00 Larger Mirror Ratio (MR) of Inboard Limited ST Plasma → More Instabilities 0.75 → Larger ⊥ Loss → Thicker SOL Z(m) B: 0.50
Divertor |B| (T) Plasma Limiter 1.5 Flux To Divertor outboard inboard 0 0 2 4 6 8 A 1 Plasma Distance Along SOL Field Line (m) Flux to SOL Flux 0.5 Limiter Surface A B Larger Geometric 30 Expansion 0 R(m) 0.25 0.5 0.75 1 1.25 1.5
20 -0.5
Plasma 10 -1 Edge Area Expansion Ratio Area Expansion 0 1.55 1.60 1.65 1.70 R (m) in SOL
ST2004-9/29-10/1/04 ST Science & Fusion Energy Increased SOL Mirror Ratio (MR) ⇒ Increased Footprint & Decreased Peak of Divertor Heat Flux
Factor of ~2 in Rdiv and MR ⇓
Factor of ~3 in ∆div
Why?
High & Low δ Divertor SOL M ≈ 3 SOL M ≈ 1.5 Bolometer Measurements R R
Rdiv (m) 0.36 0.75
SOL MR ~ 3 ~ 1.5
∆div (m) ~ 0.3 ~ 0.12
ST2004-9/29-10/1/04 ST Science & Fusion Energy Plasma Edge Studies Reveal Turbulence and “Blobs” Important to Divertor Flux Scaling Studies
105710 He manifold Broadly Based Study: • Gas Puff Imaging views along field lines (PPPL, LANL) • Very fast camera, 105/s (PSI) Side-viewing reentrant window • Reflectometers and edge (UCLA, ORNL) H-mode • Reciprocating probe (UCSD) • Divertor fast camera (Hiroshima U) L-mode • IR Cameras (ORNL), Filterscope (PPPL) • Modeling (PPPL, UCSD, LLNL, Lodestar) ST2004-9/29-10/1/04 ST Science & Fusion Energy 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
Liquid lithium tray limiter in CDX-U
Tray after ~40 discharges. PPPL, UCSD, ORNL, SNL ST2004-9/29-10/1/04 ST Science & Fusion Energy Solenoid Free Start-Up via Coaxial Helicity Injection & Outer Poloidal Field Coil Are Being Tested
Coaxial Helicity Injection Tests Three Outer Poloidal Field Startup Scenarios, e.g.: New absorber Outboard Field Null insulator installed Flux contours 20 kA
- 20 kA
Capacitor bank to be 2.8 kA installed
HIT-II Experiment CHI + OH
OH only
Culham, KAIST, Kyushu-Tokai U, PPPL, U Tokyo, U Washington 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 • JT-60U: from 200 RF Ramp-up 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 U. Tokyo, JT-60U – JAERI ST Science & Fusion Energy Nearly Sustained Plasmas with Broader Values of κ, li,Ip, and βT Can Contribute to ITER Hybrid Scenario
Co-NBI plasmas: • Improved vertical control ⇒ higher κ
• βp t 1 and IBS/Ip d 0.5
• βN ~ 6 and βT > 20% High βT • Reduced VL • Help developing ITER hybrid scenario High τ E • Driven steady state ST plasmas (CTF). • Need to reduce ELM size
ST2004-9/29-10/1/04 ST Science & Fusion Energy NSTX Made Large Progress in Producing and Studying the Science of Attractive Sustained Plasmas
NSTX Potential FY01-03 P β
½ FY04 •EFIT02
×ε • Peak βT • All shapes ~ 0.5 BS f Fraction of Self-Driven Current Fraction of Self-Driven
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
ARIES-ST (4WM/m2) NSTX Operation 4 ARIES-AT (4MW/m2) CTF-ST NSST 2 } 1 MW/m2 Normalized beta x Normalized beta normalized confinement
τpulse/τE Normalized pulse length
Well positioned to address the science of sustained high-performance plasmas.
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
Plasma Science Questions in ⇒ Optimize Fusion DEMO & Extended ST Parameter Space Development Steps How does shape determine ⇒ Lowered magnetic field and pressure? device costs How does turbulence enhance ⇒ Smaller unit size for transport? sustained fusion burn How does plasma particles ⇒ Efficient fusion α particle, and waves interact? neutral beam, & RF heating How do hot plasmas interact ⇒ Survivable plasma facing with wall? components How to supply magnetic flux ⇒ Simplified smaller design, without solenoid? reduced operating cost
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
Device NSTX NSST CTF DEMO Mission Proof of Principle Performance Energy Development, Practicality of Fusion Extension Component Testing Electricity R (m) 0.85 ~1.5 ~1.2 ~3 a (m) 0.65 ~0.9 ~0.8 ~2 κ, δ 2.5, 0.8 ~2.7, ~0.7 ~3, ~0.5 ~3.2, ~0.5
Ip (MA) 1.5 1 ~5 ~10 ~9 ~12 ~25
BT (T) 0.6 0.3 ~1.1 ~2.6 ~2.1 ~1.8 Pulse (s) 1 5 ~50 ~5 Steady state Steady state
Pfusion (MW) − ~10 ~50 ~77 ~300 ~3100 2 WL (MW/m ) − − ~1 ~4 ~4 Duty factor (%) ~0.01 ~0.01 ~15 30 60 TFC; Solenoid Multi-turn; Solenoid Multi-turn; Solenoid Single-turn; No-solen. Single-turn; No-solen.
ST2004-9/29-10/1/04 ST Science & Fusion Energy ST Research Has Broad and Growing Opportunities for Collaborations
• Exploratory ST’s in Japan MAST (U.K.) – TST-2: ECW-EBW initiation – TS-3,4: FRC-like β~1 ST plasmas MST (U.S.) – 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, τ E DIII-D (U.S.) – EBW H&CD (1 MW, 60 GHz), FY03 C-Mod (U.S.) – 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
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 optimization 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
Good Curvature Bad Curvature
Magnetic Surface Magnetic Field Line
Spherical Tokamak (ST)
Tokamak Compact Toroid (CT)
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 5 Spherical Tokamak (NSTX, MAST, TST-2, (Spherical Torus) TS-3,4, HIST, LATE, etc.) β→ (DIII-D, C-Mod,
avg Tokamak & Advanced Tokamak K-Star, JT60-U, etc.)
(QPS) Example In Design Fusion Configurations Stellarators (NCSX) Being Built (SSPX, etc.) LHD Spheromak
Reversed Field Pinch Dipole Improve Plasma Stability at High Improve Plasma (MST, etc.)
Field Reversed Configuration (LDX, etc.) 0 Average factor, Safety q (LDX, etc.)
0.5 (Applied Field)/(Applied + Plasma-Produced Field) 1 (Self-Organized) Increase Controllability → (Externally Controlled)
ST2004-9/29-10/1/04 ST Science & Fusion Energy In MAST, However, Counter NBI Reduces Electron Energy Loss Co-NBI Counter-NBI High flow shear scenario on 1.5 T 5 1.5 5 i MAST (Co- & Counter-NBI) T e 4 4 n • Counter-NBI produces stronger 1.0 e 1.0 ] -3 6 -1 3 3 ω ~ 10 s and strong local
m SE 19
[keV] reduction in χ at broader radius 2 e
2 [10 0.5 0.5 • Pressure gradient contribution to 1 1 Er reinforces that due to Vφ with .2 s #8302, 0.2 s 0.0 0 0.0 0 ctr-NBI 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 ρ ρ • Strong ExB flow shear and weak magnetic shear s ~ 0 produced 100 #88575, 0.2s 100 #8302,#830 0.2 s by NBI heating during current ramp 10 10 ]
-1 • With co-NBI ion thermal transport s
2 NC reduced to N.C. level χi ~ χi [m 1.0 1.0 with weaker reduction in χe
χ χφ i • Strong ExB flow shear ωSE > χ NCN χe i ITG 0.1 0.1 γm and s ~ 0 at minimum of χi,e 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 ρ ρ
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?
Armitage (U. Colorado)
Region to be tested
Gyrokinetic turbulence simulation in accretion disk of supermassive black hole at galactic center, assuming damping of turbulence by plasma ions vs. electrons
• 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
ST2004-9/29-10/1/04 ST Science & Fusion Energy Optimized Device Configuration Features of ST Can Fulfill the CTF Mission Effectively
Features Required by High Duty Factor & Neutron Fluence
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.
ST2004-9/29-10/1/04 ST Science & Fusion Energy