National Spherical Torus Experiment Facility / Diagnostic Overview

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National Spherical Torus ExperimentFacility /
Diagnostic Overview
Masayuki Ono For the NSTX Team 47th Annual
Meeting of Division of Plasma Physics, American
Physical Society October 24 - 28, 2005, Denver,
Colorado
College WM Colorado Sch Mines Columbia
U Comp-X General Atomics INEL Johns Hopkins
U LANL LLNL Lodestar MIT Nova Photonics New York
U Old Dominion U ORNL PPPL PSI Princeton
U SNL Think Tank, Inc. UC Davis UC
Irvine UCLA UCSD U Colorado U Maryland U
Rochester U Washington U Wisconsin
Culham Sci Ctr U St. Andrews York U Chubu U Fukui
U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu
Tokai U NIFS Niigata U U Tokyo JAERI Hebrew
U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST
ENEA, Frascati CEA, Cadarache IPP, Jülich IPP,
Garching ASCR, Czech Rep U Quebec
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NSTX Facility and Diagnostic Capabilities
Major Diagnostic Systems - Collab Confinement
Studies-tang access Magnetics for equilibrium
reconstruction Diamagnetic flux
measurement Multi-pulse Thomson scattering (30
ch) CHERS Ti(R) and Vf(r) (51 ch) Neutal
particle analyzer (2D scanning) FIReTIP
interferometer (119mm, 6 ch) Density
Interferometer (1 mm, 1ch) Visible bremsstrahlung
radiometer (1 ch) Midplane tangential bolometer
array X-ray crystal spectrometer Ti(0),
Te(0) MSE-CIF (8ch) MHD/Fluctuation/Waves High-n
and high-frequency Mirnov arrays Ultra-soft x-ray
arrays tomography (4) Fast X-ray tangential
camera (2?s) Wave reflectometers FIReTIP
polarimeter (6 ch, 600 kHz) Tangential microwave
scattering Electron Bernstein wave
radiometer Fast lost-ion probe (energy/pitch
resolving) Fast neutron measurement Locked-mode
detectors RWM sensors (n 1, 2, and
3) Edge/divertor studies Reciprocating Langmuir
probe Gas-puff Imaging (2?sec) Fixed Langmuir
probes (24) Edge Rotation Diagnostics (Ti, Vf,
Vpol) 1-D CCD Ha cameras (divertor, midplane) 2-D
divertor fast visible camera Divertor bolometer
(4 ch) IR cameras (30Hz) (3) Tile temperature
thermocouple array Scrape-off layer
reflectometer Edge neutral pressure gauges Plasma
Monitoring Fast visible cameras Visible survey
spectrometer VUV survey spectrometer X-ray
transmission grating spectrometer Fission chamber
neutron measurement Visible filterscopes Wall
coupon analysis X-ray crystal spectrometer
(astrophysics)
Device Parameters R 85 cm a 65 cm ? 1.7 -
2.7 ? 0.3 - 0.8 BT 5.5 kG ?TF (3.5 kG) 3 sec
6 ?skin Ip 1.5 MA Vp 14 m3 Ep 430
kJ PNBI 7.4 MW PHHFW 6 MW 350C
bakeout Passive Plates RWM Coils ICHI 400 kA 60
cm dia. ports Wide tang. access
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FY 05 NSTX Plasma Operations Completed
Successfully

• FY2005 Joule milestone 17 weeks Completed 18
  weeks producing 2221 plasmas.
• All the research, facility and diagnostic
  milestones completed on or ahead of schedule.
• New Research Capabilities Introduced in FY 05
  yielding exciting results
• New divertor (PF 1A) Coils for advanced shape
  control
• Error Field / Resistive Wall Mode (EF/RWM) coils
  powered by Switching Power Amplifier for plasma
  stability control
• 8 channel Motional Stark Effect(MSE) for current
  profile diagnostic
• 10 extra channels of MPTS took data
• New Research Capabilities Commissioned in FY 05
• Tangential high-k scattering system for electron
  transport physics
• Moveable glow probe became operational
• New toroidal field coil joints operated very
  reliably at 4.5 kG. The TF pulse length extended
  to 1.5 sec from 1 sec at 4.5 kG.
• TF operated up to 5.5 kG, and tested up to 5.75
  kG and the joint data being analyzed.

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NSTX Made Significant Progress in 2005

• Extension of operating regime at high ? and ?
• Significant extension of pulse-length at moderate
  current
• First experience with full set of Error Field
  Correction and RWM Control coils
• Cancellation of intrinsic error fields
• Control of rotation and effect on mode growth
• Exploration of reversed-shear regime
• Beneficial effect on electron confinement
• Contributions to physics of H-mode, ELMs,
  pedestal, confinement
• Collaborative experiments and participation in
  ITPA
• Demonstration of particle control with lithium
  coating in both limiter and divertor plasmas
• Clear demonstration of persistent current
  initiated by CHI

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Plasma shaping on NSTX is evolving toward future
reactor requirements

• Machine improvements have increased shaping factor

? 2.75, ? 0.8, S 37
2005
2004
2002-3
2001
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Modifications to poloidal field coils enable high
triangularity at high elongation

• TSC/DCON calculations indicate that simultaneous
  high ????????and ???????? will allow access to
  MHD stable 100 non-inductive regime
• Requires EBW current drive
• Highly shaped plasmas have very high wall
  stabilized ?-limits, ?N gt 8

Old PF1A Coil
Modified PF1A Coil
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Real-time EFIT enables precise boundary control

• Collaboration with General Atomics has brought
  real-time equilibrium calculations used for
  control to the ST
• Longest 1MA discharge on NSTX made using
  rtEFIT/isoflux control
• Precise control makes detailed shape variations
  possible - important research tool

Overlay of boundaries and waveforms from shots
117707 and 117814 1MA, 1s pulse length, nearly
double null plasmas controlled with
rtEFIT/isoflux control
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Upgrades to NSTX control system have enabled high
?
Graph showing the vertical stability space for
NSTX, ? b/a is the plasma elongation and li is
the normalized internal inductance. The boundary
of the data is roughly a curve of constant
vertical growth rate.

• System latency was reduced by factor of 4 from
  3ms to 0.75ms
• Have reached maximum ? 2.75 roughly equal to
  tokamak record
• High ? achieved in NSTX without internal coils or
  sophisticated control optimization

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Improved performance with increased shaping
Time averaged ?t versus pulse duration (?t is
averaged over ?pulse) sorted by shape factor S ?
q95I/aBt

• Shaping is associated with both increased time
  averaged ?t (? lt?tgt) and increased pulse length
• Pulse length has been extended to 50?E while
  maintaining high confinement and ?N
• Decrease in ?NH89 with pulse extension
  saturates, similar to tokamak performance

2002 2004 2005
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Sustained ? scales with increasing ?
Pulse averaged approximate ?sus versus 1?2 (? is
averaged over the same time window as ?sus)

• TRANSP calculations verify fbs scales according
  to approximate relationship
• Define approximate expression for sustained ?
• Approximate expression shows expected scaling
  with plasma elongation
• Gives confidence in scaling to larger devices at
  higher ?

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Record Pulse-Lengths Achieved at Moderate Current
by Operating with Sustained H-mode
ne / nGW
IP (MA)
PNBI 6 MW
VSURFACE (V)
bT 17 bP 1.5, li 0.65
bN
H89P 2-2.2 H98(y,2) 1-1.1
tE
tCurrent Relaxation
Time (s)

• H-mode with small ELMs ? lower flux consumption,
  slow density rise
• High bP increases bootstrap fraction ? lower flux
  consumption

J. Menard 
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Low Loop-Voltage Quiescent Phase Ends at Onset of
Saturated n1 Mode When qmin ? 1

• Saturated n1 mode persists for 0.5s
• Central rotation drops by factor 3
• Edge ff maintained
• bN decreases
• bN 6 above no-wall limit
• bN 4 below no-wall limit?
• qmin sustained near 1
• No sawteeth observed
• Similar to hybrid mode

Core ff (kHz)
Edge ff
bN
PNBI 6MW
qMIN without Er correction
qMIN
J. Menard, F. Levinton, S. Sabbagh 
Time (s)
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Unique and Complementary RWM Research
NSTX Passive Plates
Control coils
Control Coils
ITER plasma shape
ITER VV Profile
Columbia U
Six EF/RWM Coils powered by SPA supplies with
up to 6 kA-turn currents at 1 kHz to test
sustained operation near the wall-stabilized ?
limit Supported by unique RWM sensors (24 BR
and 24 BZ internal coils over 150 other
magnetic sensors) with 51 ch. CHERS to test
rotation effects and measure radial profile of
drag Mid-plane location, close plasma
proximity and passive plates simulate Columbia
design for RWM control in ITER where blanket
modules slow down RWMs
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Applying n1 Correction Field with External Coils
Extended Pulse Length at High bN

• With field in non-correcting directions,
  rotation is damped
• Earlier island locking and/or RWM formation

ff (carbon)

• In correcting direction, near-edge rotation
  collapse is avoided
• Extends pulselength at high-?

J. Menard, S. Sabbagh, R. Bell 
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Applied n 3 Stationary Field Used to
ControlPlasma Rotation

• Rotation stops completely in vicinity of resonant
  q 3 surface
• Neoclassical toroidal viscosity affects inner
  region
• Rotation can recover if RWM is not destabilized

W. Zhu, S. Sabbagh, R. Bell
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Heating and Current Drive Tools
HHFW f 30 MHz Prf 10 MW Pinj 6 MW
Te0 4 kV RF-H-mode Alfvénic study Edge
physics
ORNL, GA, MIT, UCSD
Worlds most sophisticated ICRF launcher Real
time antenna phase control for start-up, current
ramp-up and bulk plasma heating. Symmetric
antenna feed to improve reliability at high power
x2 power handling capability Edge and shape
control with rtEFIT Reflectometry to measure
wave propagation CD optimization with MSE
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Motional Stark Effect Diagnostic Routinely
Measures Magnetic Field Line Pitch

• 8 channels span from outer edge past magnetic
  axis
• Calibrated by NBI into neutral gas with known
  applied fields
• Between-shots analysis for q-profile
• EFIT, LRDFIT, ESC equilibrium codes
• Can include correction for Er using CHERS
  v??profile

F. Levinton, H. Yu - Nova Photonics
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51-Channel Charge-Exchange Recombination
Spectroscopy Reveals Extreme Gradients

• Diagnostic measures Ti(R), v?(R), nC(R)
• Infer nD(R) under assumption that carbon is
  dominant impurity

MPTS
51 Ch CHERS for Ti(r), V?(r)
Background Sightlines
NBI-crossing Sightlines
Resolves structure to ion gyro-radius
R. Bell, B, LeBlanc
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Transition to an Enhanced H-mode with increased
pedestal Te and Ti observed in NSTX
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Newly Installed High-k Scattering Diagnostic Will
Probe Turbulence Related to Electron Transport

• l 1mm probe beam launched tangentially near
  midplane
• Inboard / outboard launch configurations
• kr 0 20 cm-1 (in), -20 cm-1 (out)
• Superheterodyne receivers (UC Davis)
• Five channels with NF of 3000oK
• First scattered signals at end of 2005 run

H. Park, D. Smith, E. Mazzucato, C. Domier (UCD)
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Unique Power and Particle Capability with
ITER-level heat flux
Ultra-fast cameras study edge blob events
with unprecedented resolution ELM events
including divertor regions (Hiroshima U)
transient heat flux during ELMs with a fast IR
camera
Testing active power and particle control using
lithium-based tools
ITER Level
lithium pellet injection reduced oxygen 2004 -
- continues in 2004
Lithium evaporator to be implemented in 2006
Outboard Divertor Target
In-board Divertor Target
Lithium pellet moving through NSTX plasma
R(m)
ORNL
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Puffing Deuterium into Private Flux Region
Reduces Outer Divertor Heat Flux by Factor 24

• No change in inner divertor heat flux - inner leg
  already detached
• Evidence for volume recombination from increase
  in D?/D? ratio
• Divertor radiation increases but not spatially
  resolved
• Outer divertor detachment not achieved by
  midplane injection of D2 or Ne
• Ne did reduce divertor heat flux by factor 4 by
  plasma and SOL radiation

V. Soukhanovskii (LLNL) 
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Lithium from Injected Pellets Deposited on
Plasma-Facing Surfaces Provides Edge Pumping

• Fired lithium pellets (1.7 5 mg) from
  multi-barrel pneumatic injector into sequences of
  ohmically-heated helium discharges
• Limited on center-stack tiles or
  lower-single-null divertor
• After pre-conditioning surfaces with OH helium
  plasma
• 1 or 2 pellets per discharge, 24 30 mg total
  lithium in each sequence
• Dramatic reduction in density in 1st subsequent
  NB-heated deuterium gas-fueled discharge (3.5mg
  D2) in both configurations

• Effect disappeared by 3rd similar discharge
• Expected if most injected gas reacts with
  deposited lithium

H. Kugel 
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Unique Boundary Physics Capabilities
Improving core fueling is an important issue for
NSTX and future devices
D? light from SGI gas jet
Supersonic gas injector on NSTX
Super-sonic gas injector (2.4 km/sec) being
tested on NSTX. (LLNL/Princeton U) Deuterium
pellet injector CT injector proposed (U
Washiongton) (ITPA expressed interest in NSTX
demonstration)
DEGAS 2 Neutral transport modeling reproduces
observed features
Nova
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Unique Capability for Energetic Particle Research
Addresses Critical Burning Plasma Issues
NBI up to 7 MW, 60 - 100 kV, provides versatile
tool for energetic particle studies Access to
Vf gtgt VA, substantial fast particle fraction with
MSE for j(r) is unique Wide range of plasma
beta, unprecedented parameter space in Vf / VA,
?f / ?therrmal including the planned ITER
operating parameters can be investigated
2-D scanning NPA measures Ef and pitch angle
Supported by a complete diagnostic set MSE
measures crucial current profile 2-D Scanning
NPA (widest scanning) sFLIP measures lost ions
High frequency magnetic sensors
Reflectometers Fast tangential FIR
polarimeter Fast tangential soft x-ray camera
(2 ?s) Two-color ultra soft x-ray arrays for Te
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Repetitive Bursts of MHD Activity Affect Fast
Ion Population During NBI Heating

• Bursts of MHD activity detected by Mirnov coils
  are kinetic instabilities driven by population of
  fast ions
• Instabilities chirp in frequency
• Toroidal mode numbers n 2 6
• Bursts are coincident with rapid drops in DD
  neutron rate
• Mainly beam-target reactions
• NPA measures energy and pitch angle resolved
  effect on fast ions
• Depleted over wide energy range
• No Da spikes to suggest changes in edge neutral
  density

E. Fredrickson, S. Medley 
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CHI Produced Persistent Current and Closed Flux
For 10ms After the Injector Current Pulse

• Need to develop transition to control of toroidal
  equilibrium

R. Raman, B. Nelson (U. Wash.), R. Maqueda
(Nova), B. LeBlanc 
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Status and Plans

• Now entering an outage planned to last until
  December 2005
• Install lithium evaporator for coating areas of
  divertor and wall
• Build on experience in LTX (former CDX-U) and
  with LPI in NSTX
• EF/RWM Feedback Capability
• NSTX 2005 Results Review and Research Forum for
  planning experiments in 2006 will take place
  December 12 16
• Participation by our collaborators is encouraged
• Length of 2006 experimental run is not yet known
• Awaiting outcome of budget negotiations in US
  Congress