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)– (increased Landau damping of TAE)

• Acquire more information on the structure and amplitude of the modes:– Upgraded soft x-ray system– Firetip?

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,

– betaPaucity of data at high largely reflects small dwell-time at highest as well as the pathology of shots reaching high .

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

Run plan overview

Goals:Determine q-profile, density profile shape dependence of stability,

Look for Landau damping stabilization of TAE ( 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 and q, 2 shots.

B) Delayed H-mode (6 shots)

– No current ramp pause, beam power scan, 2 shots each.

C) L-mode (He puffing) (6 shots)

– One, two and three sources, 2 shots each.

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

D) 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.