Stanley M. Kaye for the NSTX Research Team PPPL, Princeton University, U.S.A.
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Transcript of Stanley M. Kaye for the NSTX Research Team PPPL, Princeton University, U.S.A.
SMK – IAEA ‘04 1
Stanley M. Kayefor the NSTX Research TeamPPPL, Princeton University, U.S.A.
20th IAEA Fusion Energy ConferenceVilamoura, Portugal
November 2004
Progress Towards High Performance Plasmas in the National Spherical Torus
Experiment (NSTX)
Supported by
Columbia UComp-X
General AtomicsINEL
Johns Hopkins ULANLLLNL
LodestarMIT
Nova PhotonicsNYU
ORNLPPPL
PSISNL
UC DavisUC Irvine
UCLAUCSD
U MarylandU New Mexico
U RochesterU Washington
U WisconsinCulham Sci Ctr
Hiroshima UHIST
Kyushu Tokai UNiigata U
Tsukuba UU Tokyo
JAERIIoffe Inst
TRINITIKBSI
KAISTENEA, Frascati
CEA, CadaracheIPP, Jülich
IPP, GarchingU Quebec
SMK – IAEA ‘04 2
NSTX Is Designed To Study Toroidal Confinement Physics at Low Aspect Ratio and High T
Aspect ratio A 1.27
Elongation 2.5
Triangularity 0.8
Major radius R0 0.85m
Plasma Current Ip 1.5MA
Toroidal Field BT0 0.6T
Pulse Length 1s
Auxiliary heating:
NBI (100kV) 7 MW
RF (30MHz) 6 MW
Central temperature1 – 3 keV
Aspect ratio A 1.27
Elongation 2.5
Triangularity 0.8
Major radius R0 0.85m
Plasma Current Ip 1.5MA
Toroidal Field BT0 0.6T
Pulse Length 1s
Auxiliary heating:
NBI (100kV) 7 MW
RF (30MHz) 6 MW
Central temperature1 – 3 keV
Establish physics database for future Spherical Torus (ST) devices
Non-solenoidal current generation/sustainment key element of program
SMK – IAEA ‘04 3
• Ip flattop ~ 3.5skin
• W flattop ~ 10 E
• T>20%, N>5, E/E,L>1.5 for ~10 E
• IBS/Ip = 0.5, IBeam/Ip = 0.1
Operational and Physics Advances Have Led to Significant Progress Towards Goal of High-T, Non-Inductive Operation
fBS = IBS/Ip = 0.5 1/2 pol
T = <p>/(BT02/20)
H-mode plasma
SMK – IAEA ‘04 4
Improved Plasma Control System Opened Operating Window During 2004 Campaign
Reduced latency improved vertical control at high-, high-T
Capability for higher allowed higher IP/aBT
Significantly more high-T
(N=6.8 %mT/MA achieved)
More routine high Longer current flattop duration pulse = (>0.85 Ip,max)
SMK – IAEA ‘04 5
T Can Be Limited by Internal Modes – Rotation Dynamics Important
• Flow shear/diamagnetic effects slow internal mode growth• Coupled 2/1, 1/1 modes eventually reduce rotation T collapse
Menard EX/P2-26
SMK – IAEA ‘04 6
Resistive Wall Modes Can Limit T at Low q
Newly installed active coils for error field/RWM control will provide means to stabilize external modes
Sabbagh EX/3-2
10% above no-wall limit for manywall times (wall ~ 5 msec)
n=1-3 components measured bynew internal magnetic sensors
- first observation of n>1
NSTX exhibits a broad spectrum of instabilities driven by fast ion resonance
Fredrickson EX 5-3
N
(G)
(G)
(G)
Bp(n=1)(deg
)B
z(G
)
n=1 no wall unstable
n=2,3
|Bp|(n=1)
|Bp|(n=2)
|Bp|(n=3)
(f<40 kHz, odd-n)
0.22 0.24 0.26 0.28t(s)
-20-10010200
100200300010
20300102030400204060
02
46
0.18 0.20 0.22 0.24 0.26 0.28t(s)
-20-10010200
1002003000
10
20010
20300102030
02
46
114147
FIG. 1
114452
Critical rotation frequency ~ 1/q2
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Systematic Scans Reveal Stored Energy Increases With Plasma Current in NBI Discharges
~ Linear dependence at fixed BT, Pinj
0
5
0.0 0.1 0.2 0.3 0.4 0.50
100
Time (s)
0
5
0
1
0.5 1.0 1.5Radius (m)
Ip [MA]
PNB [MW]
WMHD [kJ]
We [kJ]
100200
300
0
1
0
ne [1019m-3]
Te [keV]
ne [1019 m-3]
Te [keV]
SMK – IAEA ‘04 8
Parametric Dependences of NSTX Energy Confinement Time Established
Some tokamak trends reproduced in thermal and global E’s
• E exceeds tokamak scalings• L~H; L more transient• BT dependence observed
E,th/pby2 = 0.5 to 1.4
Global E from magnetics
SMK – IAEA ‘04 9
Long-Wavelength Turbulence Measured in Core for First Time in an ST Through Correlation Reflectometery
Core density fluctuations influenced strongly by magnetic fluctuations – radial correlation lengths long
Lc, ne/ne larger at lower BT
~0.45-0.7
Lc scales as s
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NSTX Has Investigated Regimes of ReducedElectron Transport
• Electron transport generally dominant (neo≤i<<e in H-mode)• Produced electron ITBs using fast current ramp, early NBI in low density (ne0~21019 m-3) L-modes
ETG modes predicted to be linearly stable in region of reversed shear(gyrokinetic calculations)
Stutman EX/P2-8
TRANSP magneticdiffusion
Reverse shear corroborated by observation of double-tearing modes
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NSTX Has Developed MSE for Current Profile Measurements at Low BT
• Preliminary reconstructions performed• Agreement with TRANSP modeling good
Equilibrium reconstruction with MSE constraint
SMK – IAEA ‘04 12
Toroidal Current Generated Without a Solenoid
1) PF-only startup 2) Transient Co-Axial Helicity Injection
- 20 kA generated - Ip up to 140 kA, Ip/Iinjector up to 40
Goal is to maintain plasma onoutside where Vloop is high
Goal is to extend Ip beyondduration of Iinjector
Non-solenoidal current generation/sustainment essential in future ST
4 5 8 10 12 146 7 9 11 13Time (ms)
1
0
100
0
0
2
4ICHI (kA)
Ip (kA)
VCHI (kV)
114374
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Hot component
Cold component
New Diagnostics/Experiments Leading to Better Understanding of HHFW Absorption
k||=14 m-1 80% 7 m-1 (ctr) 70% -7 m-1 (co) 40% -3 m-1 ~10%
Edge ion heating observed during HHFW
Impact of edge heating on HHFW absorption being studied
Absorption deficit observed during HHFW heating - Dependent on wave phase
% Absorption
Edge ion heating associated with parametric decay of HHFWinto IBW
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70 to 90% of Power Accounted for inNBI Discharges
• Most power to divertor plates (35%)
• Inner divertor detachment for ne 21019 m-3
– Reduced heat flux: 1 MW/m2
• Outer divertor always attached– qheat up to 10 MW/m2
– Attempt to detach with higher nedge &/or Prad,div
SMK – IAEA ‘04 15
A New Type of ELM With Minimal Energy Loss/Power Loading Has Been Observed
Maingi EX/2-2
D (au) Wstored (kJ)
Type “V”
Mixed Type I + Type “V”
Different ELMs reside in different regimes
SMK – IAEA ‘04 16
Significant Progress Made in Addressing ST Physics Goals and in Increasing Our Understanding of Toroidal Confinement Physics
• Improved plasma control and routine high elongation• High T and enhanced confinement for long duration (several E)
– T up to ~40%, N up to 6.8 %m T/MA– Developing understanding of -limits and methods to control MHD
modes– Developing integrated understanding of plasma transport and methods
to reduce transport• Non-solenoidal plasma startup• Regimes of reduced power loading • Current flattops for several current relaxation times
– Significant sustained non-inductive current at high-T (60% of total)
• Integration of achievements form basis for moving forward with ST concept– Many NSTX accomplishments consistent with requirements for ST
Component Test Facility (Wilson FT/3-1a,b)
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Backup
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Longer Duration High-T Achieved With Edge Density Control
• He pre-conditioning to control recycling
•Early NBI and pause in Ip ramp trigger early H-mode
• T max at IP/ITF ~ 1
T >30 % for ~2E
Large flow shear and strong gradients
observed at time of peak T 0 1 2
R (m)
Z (
m)
0
1
2
-2
-1
1.0 1.50.5R (m)
ne [1020m-3]
Ti, Te [keV]
0
1
vi [km/s]
0
0.5
0
100
200
112600, 0.55s 112600, 0.55s
0 1 2R (m)
Z (
m)
0
1
2
-2
-1
1.0 1.50.5R (m)
ne [1020m-3]
Ti, Te [keV]
0
1
vi [km/s]
0
0.5
0
100
200
112600, 0.55s 112600, 0.55s
L-H