Results from '04 in:

1
Results from '04 in

• 426 Collectively Driven fast ion losses
• 427 NTM Threshold
• 220 DIII-D CAE similarity experiment
• New diagnostic results

2
Xp426 - Collectively driven fast ion losses

• One run day with dedicated scans in beam power
  and plasma current.
• Much more data collected throughout campaign.
• No decrease of loss fraction yet seen at higher
  plasma current or beta (or "q(0)").
• More subtle correlations are being investigated.

3
Experiments have found no empirical scaling of
fast ion loss with plasma current or b

• Both TAE and chirping modes (fishbones, rTAE)
  seen to high b.
• Thermal ion Landau damping expected to stabilize
  TAE at high b.
• Precession drift reversal expected to stabilize
  chirping modes at high b bounce precession
  resonance is unaffected.
• Reduced loss at high current expected (smaller
  rpol).
• Both TAE and chirping modes contribute to fast
  ion losses in these events.

4
Xp427 - 1 day run of sawtoothing plasmas with
beta scans

• Plan was to introduce repetitive "standard"
  trigger, look for NTM excitation, growth, decay.
• Results not so clean, but very nice.
• More data added from random sawtoothing shots.
• Non-NTM n2 modes?

5
Soft x-ray data provides only internal
measurements

• Island (tearing mode) suggested by phase
  inversion in soft x-ray data.

• Mode amplitude drops substantially at sawtooth
  crashes not a feature of true NTMs.

6
Mp220 - CAE similarity study

• CAE-like modes are also found in conventional
  aspect ratio tokamaks (DIII-D).
• NSTX portion waiting for 6 kG capability.
• Beam voltage scans done at two fields.

7
New diagnostic data from this campaign.

• Poloidal array of fast Mirnov coils measurement
  of CAE poloidal structure.
• Lost one coil to grounding problem.
• Need work to understand phase shifts.
• Multi-channel heterodyne reflectometer data on
  CAE in L-mode plasmas.
• Should give internal measure of CAE (and TAE)
  mode amplitudes. Data available from at least on
  run-day.