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XP720: EBW Emission in H-Mode Plasmas

XP720: EBW Emission in H-Mode Plasmas. S.J. Diem Presented at the 2007 NSTX Results Review July 23-24, 2007. XP 720: EBW emission in H-mode plasmas. Measure 8-36 GHz thermal EBW emission via oblique B-X-O coupling

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XP720: EBW Emission in H-Mode Plasmas

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  1. XP720: EBW Emission in H-Mode Plasmas S.J. Diem Presented at the 2007 NSTX Results Review July 23-24, 2007

  2. XP 720: EBW emission in H-mode plasmas • Measure 8-36 GHz thermal EBW emission via oblique B-X-O coupling • Study behavior of EBWs emitted from H-mode plasmasat fce, 2fce and 3fce • Experiment had three objectives: • Study effect of collisions on B-X-O mode coupling • Investigate dependence of B-X-O coupling on plasma parameters • Study how bootstrap current at H-mode pedestal change fields field pitch at UHR

  3. Remotely Steered EBW Antennas Allow Angular Mapping of fce & 2 fce B-X-O Coupling Window Beam waist • ±10° scan in poloidal and • toroidal directions • Acceptance angle: • 8-18 GHz antenna ~ 22° • 18-40 GHz antenna ~ 14° Ln~3 cm Ln~7 cm Antenna spatial scan region

  4. Preliminary H-mode results show good fce and 2fce B-X-O coupling in high fBS plasmas 123544 • Target plasma: Ip=0.8 MA, ~2.5, Te~1 keV, and ne(0)~2-4x1013 cm-3 • Preliminary experimental EBW transmission efficiency given by the ratio Trad/Te(0): • ~30-50% for fce=18 GHz • ~20-40% for 2fce=28 GHz t=0.3 s L H L H

  5. Detected EBW Emission Sensitive to Drsep fce=18 GHz 124310 • Drsep reduction of 2 cm provided controlled z0 scan • Trad decreased from ~350 eV to ~100 eV with 8 cm decrease in z0 • Results similar to rapid EBE decay observed in 2006 H-modes after L H transition 2 fce=15.5 GHz 120910 L H 0 -2 -4 Z0 [cm] -6 -8 -10

  6. Increase in EBW transmission efficiency observed with LITER conditioning , 0 mg/min , 11.4 mg/min , 19.1 mg/min • Te(0)~0.8-0.9 keV • Trad increased from 40 eV (no Li) to ~300 eV for fce= 18 GHz emission • Li may decrease Ln atat EBW mode conversionlayer, widening EBWtransmission window • Similar trend observed for 2fce frequencies Density Scale Length

  7. More work needed to understand EBW mode coupling physics • Analyze the following: • Antenna scan data • Spiral antenna data • Analyze data from fce system • Do not have an absolute calibration for 8-18 GHz (fce)radiometer because of damage to microwave amplifiers at the end of run campaign; • Relative Trad data trends analysis during run still possible • Harmonic system measured absolutely calibrated fce=16-18 GHz • Correlation analysis of high time resolution reflectometer data • Perform comparison of experimental data to EBE simulation code results

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