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W. Heidbrink, R. Bell, Y. Luo * , E. Ruskov, W. Solomon, K. Burrell * , D. Liu

Fast-ion D a (FIDA) Measurements of HHFW Acceleration and Alfven-Eigenmode Transport. W. Heidbrink, R. Bell, Y. Luo * , E. Ruskov, W. Solomon, K. Burrell * , D. Liu. * (DIII-D only). FIDA complements existing diagnostics Sampler of recent DIII-D results NSTX hardware plans

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W. Heidbrink, R. Bell, Y. Luo * , E. Ruskov, W. Solomon, K. Burrell * , D. Liu

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  1. Fast-ion Da (FIDA) Measurements of HHFW Acceleration and Alfven-Eigenmode Transport W. Heidbrink, R. Bell, Y. Luo*, E. Ruskov, W. Solomon, K. Burrell*, D. Liu *(DIII-D only) • FIDA complements existing diagnostics • Sampler of recent DIII-D results • NSTX hardware plans • Proposed physics studies

  2. Fast-ion Da(FIDA) Diagnostic Measures Light from Reneutralized Fast Ions R0 • A type of Charge Exchange Recombination Spectroscopy • Use vertical view to avoid bright interferences • Exploit large Doppler shift (measure wings of line) V2 V2 Typical spectrum (1 ms integration time) • Background subtraction usually dominates uncertainty • Achieved resolution: ~ 5 cm, ~ 10 keV, 1 ms. Heidbrink, PPCF 46 (2004) 1855; Luo, RSI (2007) in press.

  3. Different Fast-ion Diagnostics Weight Phase Space Differently • FIDA: l  Vz  Perpendicular energy • A curve in (E,pitch) space contributes to a particular l • Higher energies also contribute but more weakly • Atomic cross sections also influence weighting • NPA measures a “point” in velocity space

  4. Complementarity of Fast-ion Diagnostics R0 Diagnostic Velocity Space Configuration Space Neutrons High-energy weighting Volume-average Pressure Energy weighting ~ 5 cm FIDA vz component 5 cm x 30 cm Neutrals Point Beam footprint Loss Narrow in pitch Orbit average V2 V2 Averages are useful for bulk effects on plasma; Local phase-space measurements isolate physics.

  5. Beam-beamreaction is significant when ne is low DIII-D Quiet Plasma Studies: FIDA Signal Makes Sense • Spectral shape and intensity consistent with simulation • FIDA & neutrons consistent • Expected scaling with Te, ne, beam voltage & energy Luo, Phys. Plasmas (2007) in preparation

  6. FIDA Detects Fast-ion Acceleration at 4th & 5th Cyclotron Harmonics • Neutron enhancement during ICH  fast-ion acceleration • FIDA data  distribution function distorts (Harmonic heating is expected to affect high energy ions most) • Acceleration largest ~10 cm beyond nominal resonance layer (probably due to Doppler shift and orbit effects) Heidbrink, PPCF (2007) in preparation.

  7. Alfven Eigenmodes (AE) Degrade Fast-ion Confinement R0 • Volume-averaged neutron rate is below the classical TRANSP prediction during the strong Alfven activity • During the strong Alfven activity, the fast-ion profile is nearly flat V2 V2 *Heidbrink, IAEA (2006); to be submitted to PRL

  8. NSTX Instruments: Bandpass for Time, Spectrometer for Energy/Space R0 V2 • Bandpass system integrates over wavelength--optimized for temporal resolution (< ms) • Bandpass fibers installed in 2006 • Simulation code adapted; NPA module added • Install Bandpass hardware in March • Postdoc (Mario Podesta) starts in May • Spectrometer measures full spectra across profile (10 ms) • Spectrometer operational at end of 2008 campaign? V2 Heidbrink, RSI 77 (2006) 10F120.

  9. Physics Studies with FIDA include… • The spatial profile of HHFW accelerated fast ions (also temporal & energy) • Transport at AE bursts with bandpass system • Profile flattening by AE w/ spectrometer system • Further AE similarity studies with DIII-D • Goal: Validated codes that can predict fast-ion instabilities and their consequences in ITER (and beyond).

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