A1261719908REmMq

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Transport Studies in NCSX D. R. Mikkelsen For
the NCSX Research Team NCSX PAC-8
Meeting PPPL, Nov. 9, 2006
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Overview
Goals Transport experiments in FY11 Diagnostics
needed Upgrades to enhance transport
studies Transport analysis tools Summary
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FY11 Transport-related Goals
Characterize confinement and stability
Variation with global parameters, e.g. iota,
shear, Ip, density, rotation... Comparison of
very low ripple stellarator confinement with
scalings Sensitivity to low-order
resonances Operating limits Quantify the
effects of quasi-symmetry Effect of
quasi-axisymmetry on rotation damping Effect of
quasi-axisymmetry on plasma confinement Search
for transport barriers and enhanced confinement
regimes Investigate local ion, electron, and
momentum transport
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FY11 Priorities Global Confinement
With both neutral beam heating and
ECH characterize global ?E dependence
on iota magnetic shear heating
power density beta bulk ion isotope
(H,D,He) Compare to ISS-04 scaling Also
compare to tokamak L-mode scaling ITER-97P
NCSX
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Explore ?E Dependence on Iota Shear
Vacuum
Ip150 kA
Full current
Iota and magnetic shear can be varied
independently by adjusting coil currents. Low
shear iota scan is also possible at full current.
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Will NCSX Confinement be Sensitive to iota?
W7-AS
Search for similar behavior with low shear in
NCSX. Will this also occur with large shear?
Will H-modes occur at special iota values, as
in W7-AS?
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Will NCSX Confinement Decrease with beta?
LHD
Soft equilibrium limit in both LHD and W7-AS
region with good surfaces shrinks as beta
rises. Beta 3 may be available in NCSX with
3MW (FY11). NCSX designed for large volume inside
LCFS _at_ high ?.
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Effective Helical Ripple can be Scanned by
Adjusting Coil Currents
Vary effective helical ripple, look for strong
changes in momentum confinement particle
pinch Also look for changes in ExB flow
shear energy confinement profile
stiffness transport barriers Similar to HSX
studies
?eff ()
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Effective Ripple Should Control Rotation in NCSX
HSX biased probe drives flow
low ripple
high ripple
Modulate NBI torque in NCSX measure v? with
CHERS. DNB will decouple CHERS from torque
input.
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High Ripple may Affect Heat Transport
Ion-root regime Qhel-neo ? ?eff1.5
T4.5 Negligible for the standard
configuration. Large ripple should cause
noticeable effect. More easily seen at high
temperature.
NCSX
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Local Transport studies in FY11
Will begin studies of heat and particle
diffusivities look for effect of magnetic
configuration changes. Identify regimes with
impurity accumulation. Use gas-puff source for
impurity transport studies. Compare total
bootstrap current with expected
magnitude Profile information will come from
external loops.
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Diagnostics for Transport Studies
Magnetic diagnostics provide global energy
confinement, and measure total bootstrap
current. CHERS (Ti) and Thomson scattering (Te,
ne) local heat and particle transport
analysis. CHERS toroidal rotation for momentum
transport also used to derive radial electric
field. CHERS impurity density SXR and filtered
cameras will be used for impurity transport. VUV
spectrometer and bolometer will monitor impurity
accumulation.
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Upgrades to Enhance Transport StudiesCollaboratio
n Opportunities
ECH (IPP collaboration) would enable Local
electron heating, separate ion electron
channels No fast-ion driven current or
MHD Modulated heating -gt derive diffusivity
(heat pinch?) Test profile consistency - profile
stiffness Electron-root studies HIBP (possible
NIFS/RPI collaboration) would enable Direct
determination of Er Fluctuation
studies Potential and density
fluctuations Spatial correlation lengths
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Transport Analysis Tools
Equilibrium reconstruction for Wtot and mapping
the profiles also required to provide input to
other analysis tools. D. Spongs neoclassical
transport module will be used benchmarking of
neoclassical modules maturing now. Develop
standalone neutral beam heating module several
candidates exist all need added
features. Prepare for transport analysis code.
find potential modules (ORNL, PPPL, IPP, NIFS)
identify additional features needed for
NCSX Collaborative gyrokinetic studies (IPP,
NIFS, U. Md., U. Wisc., PPPL) Coordinate work to
facilitate configuration comparisons.
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Summary FY11 Goals Achievable

• Characterize confinement and stability
• Variation with global parameters, e.g. iota,
  shear, Ip, density, rotation...
• Comparison of very low ripple stellarator
  confinement with scalings
• Sensitivity to low-order resonances
• Operating limits
• Quantify the effects of quasi-symmetry
• Effect of quasi-axisymmetry on rotation damping
• Effect of quasi-axisymmetry on plasma
  confinement
• Search for transport barriers and enhanced
  confinement regimes
• Investigate local ion, electron, and momentum
  transport