Preliminary Report on XP819: Fast ion transport induced by Alfvn avalanches

1
Preliminary Report on XP819Fast ion transport
induced by Alfvén avalanches

• E D Fredrickson
• PPPL, March 11, 2008

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Summary of results status of experiment

• Reproduced 124764 - (higher current) possibly
  higher D-fraction
• Attempted beam voltage scan in D, too difficult
  to stay out of H-mode, plagued by MHD.
  (128426-31)
• Completed beam voltage scan in He
• Found power threshold for GAE/CAE avalanches
• No TAE up to 95 kV, 2.2 MW (128433-128438)
• Source-dependence of TAE drive (swap BC)
• Still no TAE activity with source B at 95 kV.
• TAE avalanche documentation with two sources
• Power scan to avalanche threshold (128445-50)
• Power threshold about 2.7 MW vs. 2.3 for 124764.
• (Higher current?)

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Summary/status report cont.

• TAE avalanche documentation with 5-point radial
  scan of NPA.
• Avalanches kind of reproducible (128451-55)
• Document q-profile evolution, A from 240 on (shot
  128456)
• q-profile qualitatively similar to 124781 target
• RF-power scan to 2MW for Angelfish suppression
• Possibly some affect on Angelfish seen.
• Remaining major goals
• Complete q-scan dependence of threshold
• Toroidal field scan (VAlfvén) of threshold
• Initial avalanche studies in low density H-modes
• High-k scattering radial scan

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GAE avalanche threshold found

• Threshold at 75 kV, 1.5 MW, no low frequency
  modes.
• No correlation with neutron drops, ssNPA so far

• Multiple modes participate- island overlap

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5 point NPA scan completed for shots with TAE
avalanches

• Also good data with FIDA
• Avalanche power threshold higher than in '07 2.7
  MW at 75 kV.
• Neutron rate higher for similar shots possibly
  higher D fraction affecting ion Landau Damping?
• Or different q-profile?

(Helium contaminated with neon?)
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AngelsRF

• About 2 MW current drive phasing seems to affect
  Angelfish burst period.
• Preliminary result only.