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High Harmonic Fast Wave Heating on NSTX – II

High Harmonic Fast Wave Heating on NSTX – II. D. W. Swain, J. B. Wilgen (ORNL) J. R. Wilson, S. Bernabei, T. Biewer, S. Diem, J. Hosea, B. LeBlanc, C. K. Phillips (PPPL) R. I. Pinsker (General Atomics). Philip Ryan (ORNL). 46th APS-DPP Savannah, GA November 15, 2004. Outline. HHFW CD

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High Harmonic Fast Wave Heating on NSTX – II

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  1. High Harmonic Fast Wave Heating on NSTX – II D. W. Swain, J. B. Wilgen (ORNL) J. R. Wilson, S. Bernabei, T. Biewer, S. Diem, J. Hosea, B. LeBlanc, C. K. Phillips (PPPL) R. I. Pinsker (General Atomics) Philip Ryan (ORNL) 46th APS-DPP Savannah, GA November 15, 2004

  2. Outline • HHFW CD • Higher density operation at kz = 7 m-1 • Attempt CD at kz = 3 m-1 • HHFW-driven H-mode • kz = 14 m-1 • kz = 7 m-1 • HHFW + NBI • NBI into HHFW-preheated plasmas • HHFW into NBI-driven H-modes HHFW H-mode and HHFW+NBI details on Weds afternoon, poster JP1.009 (B. P. LeBlanc) PMR APS-DPP, Savannah, Nov 04

  3. Loop Voltage (corrected for dLi/dt) Te(0), <ne>, PRF solid: 112308 (co-CD) dotted: 112320 (cntr-CD) <ne> cntr-CD Te(0) co-CD PRF/10 HHFW CD at kz = 7 m-1 • Operated into double-null diverted plasmas in 2004 at 30% higher densities. • 2.7 MW at kz = -7 m-1 (co-CD) and 1.7 MW at kz = +7 m-1 (cntr-CD) gives similar Te, ne • Onset of H-mode at 0.3 s terminated CD measurement. • Loop voltage comparison for constant Ip gives DICD ~ 100 kA for DP = 4.2 MW for normalized efficiency (g) of 0.003 x 1020 A•m-2•W-1. • Te(0) = 1.7 keV • Ti(0) = 900 eV • ne(0) = 2.1x1019 m-3 • He, double-null diverted • Ip = 0.5 MA • BT = 0.45 T PMR APS-DPP, Savannah, Nov 04

  4. HHFW CD efficiency, referenced to total antennapower, is lower than predicted • CD efficiency lower than predicted by CURRAY ray-tracing code (Mau) and slightly lower than AORSA full-wave code (Jaeger). • Lower than expected efficiency related to lower power absorption on electrons at -7 m-1.[Bernabei JP1.011, Hosea JP1.012] • Using measured power absorption at -7 m-1 (~55%) and +7 m-1 (~70%) would increase the normalized current drive efficiency to 0.005 x 1020 A•m-2•W-1. Te(0) = 2 keV kz = 7 m-1 CURRAY D He 2002 AORSA 2003 2004 Details of CURRAY calculations on Weds afternoon, poster JP1.015 (T. K. Mau) PMR APS-DPP, Savannah, Nov 04

  5. Full-wave & ray tracing codes both predict improved CD efficiency for kz = 3 m-1 CURRAY (Mau) and AORSA (Jaeger) scaling study based on Te, ne profiles from shot 110145 Ti/Te = 0.7, D:H::0.96:0.04 Density scan at constant temperature Temperature scan at constant density Te(0) = 2 keV ne(0) = 2e19 m-3 PMR APS-DPP, Savannah, Nov 04

  6. 1 Need to preheat at 7 m-1 to operate at 3 m-1 Single-pass absorption (Landau damping) vs Te(0) as a function of kz, calculated for ne(0) = 2e19 m-3 • Single pass absorption for ohmic plasmas (500-600 eV) is very low for kz = 3 m-1, but around 20% for kz = 7 m-1. • Pre-heat the plasma to Te(0) ~ 2 keV with kz = 7 m-1. • Switch to kz = 3 m-1. SPA should be high (>40%) at 2 keV. • Power was lowered from 3 MW to 1.7 MW when phasing was switched to 3 m-1 to keep maximum voltage in the lines constant. 2 3 7 m-1 3 m-1 PMR APS-DPP, Savannah, Nov 04

  7. Electron heating stops after switch to 3 m-1 • Pre-heated to Te(0) ~ 2 keV with 2.5-3 MW of HHFW for 100 ms at (-7 m-1). • Fast switching to 1.7 MW at -3 m-1 Central electron temperature Line average density 112326 112327 112328 112336 112326 112327 112328 112336 HHFW HHFW ohmic ohmic ohmic -7 m-1 -3 m-1 -7 m-1 -3 m-1 PMR APS-DPP, Savannah, Nov 04

  8. Stored energy decreases and radiated power increases Stored Energy Radiated Power 112326 112327 112328 112336 112327 -7 m-1 -3 m-1 -7 m-1 -3 m-1 PMR APS-DPP, Savannah, Nov 04

  9. HHFW CD Summary • CD at kz = 7 m-1 • CD efficiency same for He and D, SND and DND plasmas. • Efficiency lower than predicted based on antenna power. • Efficiency in general agreement with predictions based on measured power absorption at 7 m-1. • CD at kz = 3 m-1 • HHFW power not absorbed by Te = 2 keV target plasma. • Single pass absorption should be adequate for this target plasma. • Density increases for 3 m-1 operation (additional gas source with RF power). • Power does not seem to be penetrating into plasma, does not show up in total stored energy. PMR APS-DPP, Savannah, Nov 04

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