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

E. D. FredricksonPPPL, 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.

• 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.

Limiter plasmas used to stay in L-mode• Soft x-ray diagnostic measures EPM amplitude.• So far, TAE not seen in SXI or Firetip

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• Strong TAE often with mild shear reversal.

• EPMs at lower q(0).

116911_0.221116903_0.250116889_0.250

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).

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).

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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 B.

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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.

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.

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.

TAE not seen with Firetip or

sxi• Mode amplitude

probably too small (probably not chord-integration cancellation).

• May provide upper limit on amplitude…

Density profile looks good for reflectometer data

• Stays in L-mode with three sources.• Weak central shear reversal in this shot.

0.000.050.100.150.200.2550100150BCDEEBDEFFBEGHBDFGHBDFGBDEFGBDDCBBBBBB CONTOURS: n/cm**3 A = 0.0000E+00 B = 5.0000E+12 C = 1.0000E+13 D = 1.5000E+13 E = 2.0000E+13 F = 2.5000E+13 G = 3.0000E+13 H = 3.5000E+13 J = 4.0000E+13 K = 4.5000E+13 L = 5.0000E+13 M = 5.5000E+13 N = 6.0000E+13 P = 6.5000E+13 Q = 7.0000E+13 R = 7.5000E+13 S = 8.0000E+13secondscmElectron Density VS time & radiusnstx 116911 page 2

• Inner reflectometer channel in low q-shear region.

• Haven't looked at data yet.

Future work

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

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.