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Preliminary Results from XP401. S.M. Kaye NSTX Physics Meeting 19 April 2004. XP401: H-mode Confinement Scaling. Objectives of first phase of experiment Establish current and power scaling of long-pulse H-mode confinement I p =0.62 – 1.2 MA, P NBI = 1 to 3 sources (at 90 keV)
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Preliminary Results from XP401 S.M. Kaye NSTX Physics Meeting 19 April 2004
XP401: H-mode Confinement Scaling • Objectives of first phase of experiment • Establish current and power scaling of long-pulse H-mode confinement • Ip=0.62 – 1.2 MA, PNBI = 1 to 3 sources (at 90 keV) • Experimental approach • Attempted with DND plasmas at k~1.9, d~0.45 (identity comparison with MAST) • Power threshold too high to perform power scan (3-3.5 MW) • Attempted with LSN at modest k, d • Discharge disrupted at 3 source level • Success with long-pulse, “PF1b” LSN discharges • k=2-2.2, d=0.5-0.7 • “Nearly” DND
XP401: H-mode Confinement Scaling • Preliminary results • Power scans with 1, 1.5 (1 source modulated), 2 and 3 performed at all currents • Did not include 1.5 source shots in preliminary results • Power thresholds near 1-1.5 source level • Type III ELMs observed for first time • Highest current, power plasma disruptive • Confinement at 1 source (with A or B) comparable; delayed L-H transition with Source C • Stored energy exhibits almost linear dependence on plasma current at fixed Ptot • Power scaling is LESS than P-0.5 at fixed Ip • Still need to sort out differences between fixed parameter scans and statistical results
Type III ELMS Observed 0.62 MA 1.5 Sources 2 Sources 3 Sources
Ip Dependence For 2 Sources 1.2 MA 1.06 MA 0.8 MA 0.62 MA
Ip Dependence For 3 Sources 1.06 MA 0.8 MA 0.62 MA
Ip Scaling of Confinement Time HL ~ IP0.74
Power Scaling HL ~ P-0.57