Transport Studies in NCSX D. R. Mikkelsen For the NCSX Research Team NCSX Research Forum

1. Transport Studies in NCSX • D. R. Mikkelsen • For the NCSX Research Team • NCSX Research Forum • PPPL, December 7, 2006 D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 1

2. 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 2

3. 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 3

4. FY11 Priorities: Global Confinement 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 D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 4

5. 1 .0 0.8 0.6 Norm. toroidal flux  r2 0.4 0.2 0.0 0.0 0.2 0.4 0.6 0.8 1 .0 Explore E Dependence on Iota & Shear Vacuum Ip=150 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. D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 5

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

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

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

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

10. 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 magnitude Profile information will come from external loops. D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 10

11. 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 11

12. Upgrades to Enhance Transport StudiesCollaboration Opportunities ECH (IPP collaboration) would enable: Local electron heating, separate ion &electron channels No fast-ion driven current or MHD Modulated heating -> 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 D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 12

13. 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 13

14. 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 Eandrotation. Check magnitude of bootstrap current. Investigate local ion, electron, and momentum transport. D. R. Mikkelsen, Transport Studies, NCSX Research Forum 2006 Page 14