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Study of TAE stability vs. central shear and q(0)

Study of TAE stability vs. central shear and q(0). Document the scaling of TAE/EPM stability with: q(0) (mode structure) Density profile (mode structure) b (increased Landau damping of TAE) Acquire more information on the structure and amplitude of the modes: Upgraded soft x-ray system

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Study of TAE stability vs. central shear and q(0)

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  1. Study of TAE stability vs. central shear and q(0) • Document the scaling of TAE/EPM stability with: • q(0) (mode structure) • Density profile (mode structure) • b (increased Landau damping of TAE) • Acquire more information on the structure and amplitude of the modes: • Upgraded soft x-ray system • Firetip?

  2. EPM/TAE induced losses seen in existing "near hybrid" scenarios • Need both: • Empirical information on parametric dependences of modes. • Ability to model effects on fast ion transport. • Study will focus on scans of: • q-profile shape, • Density profile shape, • beta • Paucity of data at high b largely reflects small dwell-time at highest b as well as the pathology of shots reaching high b.

  3. Previous experiment found suggestion of toroidal mode number scaling • At 0.5 MA, toroidal mode numbers from 1 to 6. • At 1.0 MA, toroidal mode numbers from 3 to 6. • Data not that clean… 0.5 MA 1.0 MA

  4. Run plan overview Goals: Determine q-profile, density profile shape dependence of stability, Look for Landau damping stabilization of TAE (b scan) (Reference shot tbd, based on early shots in campaign) ) Early H-mode, fast current ramp. (8 shots) • One, two and three sources, 2 shots each. • Delay third source, decouple b and q, 2 shots. B) Delayed H-mode (6 shots) • No current ramp pause, beam power scan, 2 shots each. • L-mode (He puffing) (6 shots) • One, two and three sources, 2 shots each.

  5. Run plan overview (cont.) D) Slower current ramp, delayed H-mode (6 shots) • Let qmin drop lower, decide based on amount of change seen in A-D. Or • Beam voltage scan (? shots) • Choose best case from A-D, drop beam voltage to 70 kV, then up or down 5 kV. Source A still at 90 kV, but on-time delayed until peak of MHD activity. • Also, consider how much time is left.

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