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Report on xp517: Study of TAE stability vs. q shear and q(0)

Report on xp517: Study of TAE stability vs. q shear and q(0). E. D. Fredrickson PPPL, Aug. 8, 2005. Quick Summary of Status. Variations in beam injection time did result in "control" of q(0). TAE/EPM activity showed changes correlated with variation of q(0). TAE at high q(0), EPM at low.

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Report on xp517: Study of TAE stability vs. q shear and q(0)

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  1. Report on xp517:Study of TAE stability vs. q shear and q(0) E. D. Fredrickson PPPL, Aug. 8, 2005

  2. Quick Summary of Status • Variations in beam injection time did result in "control" of q(0). • TAE/EPM activity showed changes correlated with variation of q(0). • TAE at high q(0), EPM at low. • Maintaining L-mode without He puffing was difficult. • Soft x-ray emissivity was low in L-mode plasmas. • Secondary goal of documentation of internal amplitude and structure was poorly realized.

  3. Limiter plasmas used to stay in L-mode • Soft x-ray diagnostic measures EPM amplitude. • So far, TAE not seen in SXI or Firetip • Strong TAE often with mild shear reversal. • EPMs at lower q(0). 116911

  4. q(0) ≈ 1;classic fishbones • Large variation in neutron rate response; evolution in fast ion distribution or in mode structure? • Virtually no TAE activity (with 3 neutral beam sources).

  5. At higher q(0),cw EPMs • EPMs still n=1; infernal fishbones? • Convert to saturated EPMs later - possibly correlated with higher q? • Internal diagnostics include soft x-rays and Firetip. • Weak TAE activity earlier (1 source). 116903

  6. Firetip/sxi can detect EPMs • Important to have some internal, direct, measure of mode amplitude. • Soft x-rays can also provide information on mode structure. • Earlier chirps (0.28 & 0.3s) apparently weaker than cw mode; similar amplitude for dB. 116903

  7. Moderate q(0), H-mode:mixed TAE/EPM • May also be some density, density profile dependence for TAE. • "H-mode onset" about 210 ms. • Weak soft x-ray emission • Reflectometers looking near plasma edge. • May not be enough data.

  8. High q(0); TAE-like modes • This shot was anomaly, slow current penetration even with late beam injection. • L-mode density profile means potentially useful reflectometer data. • TAE still chirping, maybe more like rTAE.

  9. High q(0):TAE or rTAE • TAE-turbulence • Chirping modes at TAE frequencies suggest resonant TAE, rTAE. • Large neutron drop correlated with EPM; TAE seem to usually have small impact on fast ion confinement.

  10. TAE not seen with Firetip or sxi • Mode amplitude probably too small (probably not chord-integration cancellation). • May provide upper limit on amplitude…

  11. Density profile looks good for reflectometer data • Stays in L-mode with three sources. • Weak central shear reversal in this shot. • Inner reflectometer channel in low q-shear region. • Haven't looked at data yet.

  12. Future work • Finish sorting and categorizing. • Check out reflectometer data. • TRANSP runs to find fast ion distributions. • Input to M3D, Nova, etc.

  13. q(0) ≈ 1;Classic fishbones? • TAE present, but weak. • Fishbone becomes a saturated EPM; consistent with theoretical models and seen previously at high aspect ratio. • Possibly sawteeth later.

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