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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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Confinement ScalingExperiments on NSTX Stanley M. Kaye PPPL, Princeton University ITPA Meeting Lisbon, Portugal 8-10 November 2004 1
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
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
Stored Energy Increases Linearly With Plasma Current 2 NBI Sources Linear Ip scaling for three sources as well 5
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
Thermal Confinement Times Exhibit Similar Parametric Trends Thermal tE determined by TRANSP (126 discharges ‘TRANSPed”) ~25% uncertainty on tE,th 7
BT Dependence Observed For Both Global and Thermal Confinement Are magnetic fluctuations important? 8
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?
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
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
Global L-mode Scaling Also Exhibits Strong BT Dependence (all BT), And Linear Ip Dependence Database not complete enough for tEth scaling 12
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
Magnetic Shear Can Modify Plasma Transport Properties and Lead to Internal Transport Barriers Low Density (ne0~21019 m-3) L-mode TRANSP magnetic diffusion 14
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
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
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
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