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Scoping Study of Ohmic H-modes on NSTX

Scoping Study of Ohmic H-modes on NSTX. C. E. Bush, R. Maingi, S. Kaye, T. Biewer, B. LeBlanc, S. Zweben, et al. And the NSTX Research Team. Goals of Ohmic H-mode Scoping XP. Document the parameter/configuration effects on Ohmic H-modes: Plasma current dependence of transition and properties

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Scoping Study of Ohmic H-modes on NSTX

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  1. Scoping Study of Ohmic H-modeson NSTX C. E. Bush, R. Maingi, S. Kaye, T. Biewer, B. LeBlanc, S. Zweben, et al. And the NSTX Research Team

  2. Goals of Ohmic H-mode Scoping XP • Document the parameter/configuration effects on Ohmic H-modes: • Plasma current dependence of transition and properties • Effect of divertor formation time vs Ip flattop time • Are profiles at L-mode to OHH-mode same as L- to H-? • Observed OH powers. • Determine applications of Ohmic H-modes in other experiments: • Early injection • Combined Edge and Core Transport Barrier Plasmas • Are formation and behavior of OHH-modes robust?

  3. OHH-mode with Dithers (DND)

  4. ELM-Free OHH-mode (LSN)

  5. Observations on Ohmic H-modes • First OH H-modes obtained in double null configuration (diverted): • Easier to obtain this run (conditioning? Reduced B errors?) • Modest Ip and Bt • Early-in-run OHH-modes ELM free or large ELMs • Easier to obtain at higher Ip: • Fewer and larger ELMs at high Ip • Small high frequency ELMs (dithers) at low Ip • (Is this indication of near-threshold power?) • Determine applications of Ohmic H-modes in other experiments: • Early injection - would the OHH-modes be good targets? • Are formation and behavior of OHH-modes robust? • Combined Edge and Core Transport Barrier Plasmas

  6. Overview of Run Plan for OH H-modes • Determine a DND target and a LSN target • Reproduce 111588 (DND) - 2 shots • Reproduce 111307 (LSN) - 2 shots • Optimize time of transition for application (DND) - 6 shots • Parameter Scans (DND) • Ip scan 600 kA, 900 kA 2+2 = 4 shots • Bt scan 0.30 T, 0.45 T 2+2 = 4 shots • Repeat B. and C. above for LSN - 20 shots • Application: (Need NBI at this point; could be another day) • Early injection using best results above (determine NBI) 5 shots • Combined Edge and Core Barriers - use best results above 6 shots Need available - 100 kV (heat core), 60 kV (other heat) Different from early injection shots

  7. Concerns • Obtaining OHH-mode at desired time • Optimize time of transition for application (DND) - • Parameter Scans (DND) • Ip scan 600 kA, 900 kA • Bt scan 0.30 T, 0.45 T • Repeat B. and C. above for LSN - • Application: (Need NBI at this point; could be another day) • Early injection using best results above (determine NBI) 5 shots • Combined Edge and Core Barriers - use best results above 6 shots Need available - 100 kV (heat core), 60 kV (other heat) Different from early injection shots

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