D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 1Columbia U.

Transport Studies in NCSX

D. R. Mikkelsen

For the NCSX Research Team

NCSX Research ForumPPPL, December 7, 2006

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 2Columbia U.

Overview

Goals

Transport experiments in FY11

Diagnostics needed

Upgrades to enhance transport studies

Transport analysis tools

Summary

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 3Columbia U.

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 plasma confinement

Effect of quasi-axisymmetry on rotation damping

Search for transport barriers and enhanced confinement regimes

Investigate local ion, electron, and momentum transport

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 4Columbia U.

FY11 Priorities: Global Confinement

Characterize global E dependence on:iotamagnetic shearheating powerdensitybetabulk ion isotope (H,D,He)

Compare to ISS-04 scaling:

Also compare to tokamakL-mode scaling: ITER-97P

NCSX

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 5Columbia U.

Explore E Dependence on Iota & Shear

Iota and magnetic shear can be varied independently by

adjusting coil currents.

Low-shear iota scan is also possible at full current.

0.0 0.2 0.4 0.6 1.00.8

0.0

0.2

0.4

0.6

1 .0

0.8

Norm. toroidal flux r2

Vacuum Ip=150 kA Full current

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 6Columbia U.

Will NCSX Confinement be Sensitive to iota?

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?

W7-AS

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 7Columbia U.

0.001

0.01

0.2 0.4 0.6 0.8 1

M45_HiEpsm50Z01e04t8g

r/a

Standard configuration

Effective Helical Ripple can be Scanned by Adjusting Coil Currents

Vary effective helical ripple,look for strong changes in:

momentum confinementparticle pinch

Also look for changes in:ExB flow shearenergy confinementprofile stiffnesstransport barriers

Similar to HSX studies

eff

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 8Columbia U.

Effective Ripple Should Control Rotation in NCSX

Modulate NBI torque in NCSX; measure v with CHERS.

DNB will decouple CHERS from torque input.

HSX biased probe drives flow

low ripple

high ripple

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 9Columbia U.

High Ripple can Affect Heat Transport

Ion-root 1/ 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

0

1

2

3

4

5

0 0.2 0.4 0.6 0.8 1r/a

axisymmetricneoclassical

neoclassical ripple

Anomalous

0

1

2

0 0.2 0.4 0.6 0.8 1

Te

Ti

Pinj

=6 MW

Ro=1.4 m B

o=1.2 T

<β>=4% . mini*=0.25

ne=6 10x 19 m-3

H-95ISS

=2.9 H-97ITER P

=0.9

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 10Columbia U.

Local Transport studies in FY11

Will begin studies of heat and particle diffusivities as profile diagnostics become available; 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 magnitudeProfile information will come from external loops.

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 11Columbia U.

Diagnostics for Transport Studies

Magnetic diagnostics provides global energy confinement,

and total bootstrap current.

CHERS (Ti) and Thomson scattering (Te, ne) : local heat-

and particle-transport.

CHERS toroidal rotation for momentum transport;

also used to infer radial electric field.

CHERS impurity density, SXR, and filtered cameras will be

used for impurity transport.

VUV spectrometer, bolometer and SXR will monitor

impurity accumulation.

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 12Columbia U.

Upgrades to Enhance Transport StudiesCollaboration Opportunities

ECH (IPP collaboration) would enable:Local electron heating, separate ion &electron channelsNo fast-ion driven current or MHDModulated heating -> derive diffusivity (heat pinch?)Test profile consistency - profile stiffnessElectron-root studies

HIBP (possible NIFS/RPI collaboration) would enable:Direct determination of Er

Fluctuation studiesPotential and density fluctuationsSpatial correlation lengths

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 13Columbia U.

Transport Analysis Tools

Magnetic analysis for Wtot and profile mapping;provides input to other analysis tools.

D. Spong’s neoclassical transport module will be used;benchmarking of neoclassical modules maturing now.

Must develop standalone neutral beam heating module;several candidates exist; all need added features.

Prepare for development of a 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.

D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 14Columbia U.

FY11 results will guide NCSX’s future

Characterize confinement and stability over broad operating space.

Compare NCSX confinement with stellarator and tokamak scalings.

Quantify the effects of quasi-symmetry on E and rotation.

Check magnitude of bootstrap current.

Investigate local ion, electron, and momentum transport.