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XP-720: EBW B-X-O mode coupling in H-mode discharges

XP-720: EBW B-X-O mode coupling in H-mode discharges. Investigate collisional effects on B-X-O mode coupling LPI conditioning has shown increase in EBE Gas valve near antennas available; will be used for remaining run time

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XP-720: EBW B-X-O mode coupling in H-mode discharges

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  1. XP-720: EBW B-X-O mode coupling in H-mode discharges • Investigate collisional effects on B-X-O mode coupling • LPI conditioning has shown increase in EBE • Gas valve near antennas available; will be used for remaining run time • Bootstrap current from pressure gradient at H-mode pedestal may change field pitch at UHR • Wide acceptance angle antenna to detect EBE outside steered antenna field of view • Investigate effects of plasma parameters on B-X-O coupling • Initial outer gap scan has shown small increase in emission • Vertical position scan started • Only -2.8 cm scan achieved • Proposed at least ±3 cm

  2. Preliminary H-mode results show increase in B-X-O coupling with Li conditioning • Reference shot (123148): Te(0)=1 keV, ne(0)~4-6x1013 cm-3, Ip=1MA • 3.4 mg Li pellet injection (LPI) into ohmic He L-mode plasma for conditioning • 1st shot after LPI, 123153, exhibited 2x increase in EBE • 2nd shot after LPI, 123154, EBE reverted to pre-Li conditions Reference shot 1st after 3.4 mg LPI 2nd after 3.4 mg LPI Li conditioning reduces ELM's and increases edge Te - possibly reducing effects of EBW collisional damping. EBE modeling ongoing.

  3. Preliminary H-mode results show good fce and 2fce B-X-O coupling in high , fBS plasmas • Target plasma (with LITER): Ip=0.8 MA, k~2.5, Te~1 keV, ne(0)~2-4x1013 cm-3 • Preliminary experimental B-X-O coupling efficiency: • 30-50% for fce=18 GHz, 2fce=28 GHz • EBE simulation work is ongoing t=0.3 s shot 123544 2fce=28 GHz L-H transition More near-term experiments to focus on studying this target plasma. Antenna location will be scanned to optimize emission.

  4. Remaining run time focused on optimizing B-X-O coupling in H-mode plasmas • Excellent H-mode target identified; scans required to optimize emission and understand coupling physics • Target - 123544: Ip=0.8 MA, Te(0)~1keV, ne(0)~2-4x1013 cm3, k=2.5 with LITER conditioning Shot # Description 1-2 Shot development 3-12 Antenna scan 13-15 Vertical position scan - at least ±3 cm 16-17 Outer gap scan - +1 cm and - 3 cm • Required diagnostics: • EBW radiometers • Thomson scattering • Reflectometer

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