1 / 18

XP-720: EBW Coupling at 8-36 GHz in H-Mode Plasmas

XP-720: EBW Coupling at 8-36 GHz in H-Mode Plasmas. Steffi Diem Waves ET Meeting March 29 rd , 2007. Very Low B-X-O Coupling Measured During H-mode Plasmas in 2006. <10% coupling efficiency measured during I p flattop (after emission burst)

talisa
Download Presentation

XP-720: EBW Coupling at 8-36 GHz in H-Mode Plasmas

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. XP-720: EBW Coupling at 8-36 GHz in H-Mode Plasmas Steffi Diem Waves ET Meeting March 29rd, 2007

  2. Very Low B-X-O Coupling Measured During H-mode Plasmas in 2006 • <10% coupling efficiency measured during Ip flattop (after emission burst) • Emission unpolarized after t~0.25s, indicating diagnostic measuring scattered emission H-Mode Possible causes: collisional damping, edge bootstrap current effects

  3. Data Mining Suggests Reduced Emission May be Coupled to Z-Position • Emission burst occurs for z(0)>-2 cm and decays when z(0)<-2 cm • Possibly similar to results observed during EBW heating experiments on TCV 120910 121227 - decaying EBE 117970 - 30% [2005] 120910 - EBE burst

  4. Slowly Decaying EBE H-Mode Shot Observed • Emission slowly decays during discharge • Coupling efficiency drops from 40% to 15% • Antenna pointing direction not optimized • Similar to refraction effects observed on MAST • "Prospects of EBW Emission Diagnostics and EBW Heating in Spherical Tokamaks", V.F. Shevchenko, et. al. 121227 fce=15.5 GHz

  5. Low EBE During H-Mode will be Investigate During 2007 NSTX Run Campaign • Investigate collisional effects on B-X-O mode coupling • Li pellet injection will be used to modify edge Te and change collisionality at B-X-O mode conversion layer • Investigate effects of plasma parameters on B-X-O coupling • Bootstrap current from pressure gradient at H-mode pedestal may change field pitch at UHR: • Pitch may be large enough to move B-X-O emission window outside antenna acceptance angle • Install wide acceptance angle spiral antenna to detect EBE outside acceptance angle Research will support an invited talk at the 17th Topical Conference on RF in Plasmas on May 7-9th, 2007

  6. H-Mode Run Plan 2007 Campaign • Run plan (36 shots ~ 1 day) 1-5 Shot development of bursting EBE H-mode (122939) 6-7 Optimize antenna alignment 8 Reflectometer/reciprocating probe data shot Vertical position scan using rtEFIT: 9-10 - start with target discharge, move z(0) +2 to +3 cm 11 - repeat for reflectometer and reciprocating probe 12-13 - use rtEFIT to move vertical position +0 to +6 cm during Ip flattop 14-15 - start with target discharge, move z(0) -2 to -3 cm 16 - repeat for reflectometer and reciprocating probe 17-18 - use rtEFIT to move vertical position +0 to -6 cm during Ip flattop

  7. H-Mode Run Plan 2007 Campaign • Run plan (36 shots ~ 1 day) - continued Outer gap scan: 19-20 - Increase outer gap by +5 cm 21-22 - Increase outer gap by +10 cm 23-24 - Decrease outer gap to 5 cm Bootstrap current scan: 25-26- introduce later gas fueling during current flattop to increase edge collisionality 27-28 - starting with target discharge, increase k to 2.5 29-30 - starting with target discharge, TF ramp 4.5 to 5.5 kG 31-33 - add gas fueling, k~2.7, and TF ramp 4.5-5.5 kG 34 - repeat for reflectometer and reciprocating probe 35-36 - Introduce early H-L transition halfway through Ip flattop

  8. Diagnostic Requirements • EBW antennas • 8-18 GHz system • 18-36 GHz system • spiral antenna system • 30-point Thomson scattering • Magnetics (for EFIT) • Reflectometer (ORNL & UCLA) • Fast reciprocating probe • MSE

  9. Extra Slides

  10. 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

  11. 2006 Scan of H-Mode Window Indicates Very Low Emission • Target discharge: Ip~1MA, Te(0)~0.9 keV, ne(0)~5e13 m-3 • Burst of emission observed shortly after L-H transition 120910

  12. Slowly Decaying EBE H-Mode Shot Observed • Discharge characteristics: Ip=1MA, Te(0)~1keV, ne(0)~4e1013 m-3 Shot 121227 t=0.3 s

  13. Quiescent H-Mode from Previous Run Good Target Discharge • Fluctuation free edge • Steep edge gradients • Improve B-X-O coupling 117260

  14. H-L Transition May Provide Insight to Understanding B-X-O Coupling in H-Modes H-L • Event at t=0.35 s kills B-X-O emission For 2007 develop disruption-free discharge with H-L transition for bursting H-modes

  15. H-L Transition May Provide Insight to Understanding B-X-O Coupling in H-Modes • Discharge characteristics: Ip~750 kA, H-L transition at t~0.33s H-L 120217

  16. 120215 H-L t=0.42s t=0.3s

More Related