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Stanley M. Kaye PPPL, Princeton University ITPA Meeting Lisbon, Portugal 8-10 November 2004

Confinement Scaling Experiments on NSTX. Stanley M. Kaye PPPL, Princeton University ITPA Meeting Lisbon, Portugal 8-10 November 2004. Confinement Scaling Experiments Planned and Carried Out. H-mode scaling Part of NSTX/MAST identity experiment Examine specific parametric trends

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Stanley M. Kaye PPPL, Princeton University ITPA Meeting Lisbon, Portugal 8-10 November 2004

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  1. Confinement ScalingExperiments on NSTX Stanley M. Kaye PPPL, Princeton University ITPA Meeting Lisbon, Portugal 8-10 November 2004 1

  2. Confinement Scaling Experiments Planned and Carried Out • H-mode scaling • Part of NSTX/MAST identity experiment • Examine specific parametric trends • Use results from systematic scans + other discharges to develop scalings • Also L-mode • Dimensionless scaling • bt, n* • r*(NSTX/DIII-D similarity) 2

  3. NSTX Device Characteristics and Parameters 3

  4. Systematic Parameter Scans in H-mode Plasmas Performed • Run as part of NSTX/MAST identity experiment • Plan to run in DND, k~1.9, d~0.4 • DND not viable due to high PLH threshold • Lower k not viable at high power (disruptive) • LSN w/ PF1b (k~2.1) • Ip scan at fixed P, BT (0.45 T) • 0.6 to 1.2 MA in 4 steps • Scans at both 2 and 3 NBI sources • P scans at fixed Ip, BT (0.45 T) • Full scans at Ip=0.8, 1.0 MA • Used modulated NBI if necessary to establish low power H-mode between 1 and 2 steady sources (i.e., 1 ½ sources) 4

  5. Stored Energy Increases Linearly With Plasma Current 2 NBI Sources Linear Ip scaling for three sources as well 5

  6. Some Confinement Trends Found to be Similar to Those at Conventional Aspect Ratio Expand database to include other discharges Study global dependences of global confinement time (EFIT) (~10% “random” uncertainty on tEmag) 6

  7. Thermal Confinement Times Exhibit Similar Parametric Trends Thermal tE determined by TRANSP (126 discharges ‘TRANSPed”) ~25% uncertainty on tE,th 7

  8. BT Dependence Observed For Both Global and Thermal Confinement Are magnetic fluctuations important? 8

  9. Core Density Fluctuations Influenced Strongly by Magnetic Fluctuations • Turbulence correlation lengths long • Lcr, Dne/ne larger at lower BT • Long-l turbulence measured in core for first time in an ST through correlation reflectomtery • High correlation between magnetic and reflectometer phase fluctuations r~0.45-0.7 r~0.45 Lcr scales asrs 9 Transition from e-s to electromagnetic dominated core in finite-bT NSTX?

  10. Strong BT and Weaker Ip Dependence In Regressions  Ip0.65 BT0.45 for both if dataset constrained to BT>0.31 T • Ip1.0 BT00.95 ne0.05 P-0.50 Ip1.1 BT01.50 P-0.50(no error) • Ip0.79 BT00.71 ne0.16 P-0.49 Ip0.66 BT01.07 P-0.36(error) (Principal Component Analysis) 10

  11. Comparison With “New” H-mode Scalings (from Cordey IAEA) All data tEth (sec)  P-0.61  P-0.45 ELMy H-mode scalings - Cordey 11

  12. Global L-mode Scaling Also Exhibits Strong BT Dependence (all BT), And Linear Ip Dependence Database not complete enough for tEth scaling 12

  13. Transport Properties of NSTX Plasmas Are Also Being Studied • Electrons dominate loss in most H-modes • cNCLASS ≤ ci << ce • Electron transport higher at lower BT? Ion transport lower? • CHERS recalibration continuing 13

  14. Magnetic Shear Can Modify Plasma Transport Properties and Lead to Internal Transport Barriers Low Density (ne0~21019 m-3) L-mode TRANSP magnetic diffusion 14

  15. To Do • Combine 2004 data with previous data to try to verify BT scaling • Quantify MHD activity • Understand difference between systematic scan and MLR Ip dependence • Other hidden parameter dependences • ELMs • Rotation • Compare to MAST results at similar powers, currents • Later this year • Recalibration of CHERS data (Ti, ….) • Recalculate tE,thermal, cs, and submit to ITPA database 15

  16. TF Limited to ≤ 0.45 T in 2004 Campaign • BT scan (fixed Ip and fixed q) not carried out • Required BT ~ 0.55 T • Dimensionless Scaling Experiments Planned But Not Carried Out • Study dependence of confinement and transport on b, holding other dimensionless variables fixed as much as possible • Understand basis for observed transport • Differentiate between electrostatic and electromagnetic turbulence induced transport • Gain confidence in predictions to larger devices • Bte,th ~ v*0.35b-0.35 16

  17. n* Scan • Change n* by varying n and BT (assuming concomitant change in Te with BT) • Adjust PNBI in order to maintain bT, r* (i.e., T ~ B2) • High n*, low bT (“high” n) BT = 0.55 T, Ip = 1.1 MA, PNBI = 2 to 3 sources II)Low n*, low bT (“low” n) BT = 0.35 T, Ip = 0.7 MA, PNBI = 1 sources 17

  18. b Scan Change Ip/BT (fixed q, geometry) at constant beam power I) Low bT (from n* scan) BT = 0.55 T, Ip = 1.1 MA, PNBI = 2 to 3 sources II) High bT BT = 0.35 T, Ip = 0.7 MA, PNBI = 2 to 3 sources III) Medium bT BT = 0.45 T, Ip = 0.9 MA, PNBI = 2 to 3 sources LSN, k ~ 1.9, d ~ 0.6 18

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