1. D-Alpha Fast-Ion Diagnostic: Recent Results from DIII-D W.W. Heidbrink, UC Irvine D-Alpha Diagnostic: Yadong Luo, K. Burrell, + Ion Cyclotron Heating: R. Pinsker, C. Petty, P. Politzer, M. Murakami, + Fast-ion instabilities: R. Nazikian, M. van Zeeland, T. Rhodes, G. McKee, E. Fredrickson, E. Synakowski, + Diagnostic Concept Classical Fast-ion Distribution RF Acceleration Spatial Profile during Instabilities

2. THE FAST-ION DISTRIBUTION IS UNCERTAIN IN MOST AT DISCHARGES Nucl. Fusion 42 (2002) 972. Ad hoc diffusion model matches neutron rate. Introduces uncertainties in pressure and current profile control and analysis.

3. Bright Backgrounds: Injected, Halo, and Edge Neutrals What viewing geometry Doppler shifts the relatively dim fast-ion light away from these backgrounds?

4. Exploit gyro-motion: use a vertical view Notch filter blocks light from other neutrals (dynamic range) Beam modulation to subtract bremsstrahlung and edge impurity lines

5. Diagnostic Concept Demonstrated: 2003 data from a radial view PPCF 46 (2004) 1855. Fast-ion feature has expected temporal, spectral, and density dependencies. Signal weak at high density (>7x10 19 m -3 )

6. Atomic Physics Processes Neutralization depends on relative velocity between injected neutrals and fast ions. Intrinsic spatial resolution ~5 cm. Doppler shift determined by velocity component along line of sight. Stark broadening of minor importance

7. D  Instrumentation for 2005 Campaign New dedicated 2-channel instrument with full spectra. 8 spatial CER channels with partial spectra (tuned to D  sometimes)

8. Complications in the Interpretation of the Signal Ideally, the fast-ion density would be proportional to the signal, BUT … The injected neutral density depends on the beam deposition The Doppler shift depends on only one velocity component Impurity lines can contaminate the spectrum ELMs can complicate the background subtraction

9. “Boring” Shot with Classical Fast- ion Behavior

10. Spectra from Spatial Array in Quiet Plasma Signal visible from edge to center

11. Spatial Profile in Quiet Plasma Looks Reasonable Signal integrated from 40-80 keV and over 1.5 s. Geometrical corrections omitted.

12. Velocity-space weighting depends on pitch-angle scattering rate Competition between deceleration (T e ) and pitch- angle scattering (Z eff ) determines fraction of velocity space occupied by perpendicular ions

13. Quiet shot with T e Variation 50 keV perpen dicular neutrals

14. Expected Qualitative Dependence on Electron Temperature

15. No Prominent Contaminating Lines in Spectrum Single 1 ms spectrum Background subtraction works well for low charge states. CER lines for E>80 keV

16. Resumed High Harmonic Heating Experiments in 2005 60 MHz System Injected > 1 MW into L-Mode plasmas and ~0.6 MW into AT target. Studied beam-ion acceleration at 4 th -6 th harmonics 2 nd harmonic hydrogen acceleration (by accident!) 116 MHz System Injected ~ 2 MW into L-Mode plasmas Little beam-ion acceleration at 7 th and 8 th harmonic

17. Beam-ion Acceleration during 4 th harmonic heating

18. D  Spectrum: Perpendicular Fast- ion Tail during 60 MHz ICH Tail spectrum symmetric--expected for perpendicular ions Spectrum altered at high energies (high harmonic heating) Signal increases 75% with RF Ions accelerated above injection energy Tail correlates with neutron enhancement

19. MANY FAST-ION INSTABILITY EXPERIMENTS WERE COMPLETED Many low-field and reversed shear experiments. New internal fluctuation diagnostics: BES, interferometers, FIR scattering, reflectometry. Fast-ion diagnostics: D-alpha, neutral-particle, neutrons, edge-loss. CAEs are common at low field. Cascade modes are common in reversed and weak shear.

20. “Nasty” Low-field shot with virulent internal kink activity

21. Bizarre Profile with Virulent Instabilities Preliminary: Need improved background subtraction

22. Fast-ion D-Alpha measurements are a very promising technique Technique works best for devices with ~30 keV/amu beams, modulation capability, modest densities, and size >> 5 cm (like DIII-D & NSTX). In quiet plasmas, deposition and T e dependence look reasonable. Need detailed analysis to confirm. Tail populations accelerated by ICRF are readily observed. Will compare with predicted acceleration. We measured fast-ion spatial profiles during CAE, Cascade, internal kink, ITB formation, and helical-field (ELM suppression) experiments. Hope to use internal instability measurements to compare with predicted fast-ion transport.

23. Alfven cascade modes (cylindrical modes at q min ) observed in DIII-D Barely visible on magnetics Clearly seen on internal diagnostics: FIR scattering, interferometers, BES, PCI. Driven by sub-Alfvenic fast ions at full field. Doppler shifts indicate high toroidal mode numbers. Cascade data assist in determination of q profile Nazikian et al., IAEA (2004). NEW FLUCTUATION DIAGNOSTICS

24. CAE ARE OBSERVED ON DIII-D: WILL THESE BE EXCITED IN ITER? Very similar to NSTX instabilities. Agrees qualitatively with CAE theory. Suggest alphas will drive CAE in ITER.