ITPA Diagnostics 4/06

The Importance of Fast-Ion Profile Measurements in ITER

W. Heidbrink

•Three examples from DIII-D

•Conclusion

Fast-ion D (FIDA) Technique

Heidbrink, PPCF 46 (2004) 1855.

ITPA Diagnostics 4/06

The Fast-ion Profile is Not a Flux Function

•Even without instabilities, in current devices, the fast-ion density profile is not a flux function.

•With instabilities, wave-particle resonances occur preferentially with some classes of particles (e.g., co-passing alphas interact more strongly with TAEs than counter-passing alphas).

•The resultant transport alters the spatial profile in a non-uniform fashion.

Kiptily, NF 45 (2005) L21

JET Gamma-ray Data

ITPA Diagnostics 4/06

Fast-ion Redistribution Occurs in Current Devices

•Three discharges withdifferent levels of modeactivity•Fast-ion redistributionbroadens current profile•Optimal redistributiontriggers an internaltransport barrier•Calculations suggest asimilar phenomenon may occur in ITER.

Wong, NF 45 (2005) 30.

DIII-D Magnetics Data

MSE-derived equilibria

ITPA Diagnostics 4/06

Fast-ion Profile Flattens in Fully-Noninductive, High-Performance AT Discharge

•Flattening occurs inhighest beta phase•Neutron rate deviatesFrom TRANSP predictionduring this phase•Integrated FIDAsignalshows profile becomesflat•Agrees with analysis of driven beam current: Need flat beam density profile to match current profile

Classical

Data

Murakami, Phys. Pl. 13 (2006) in press.

DIII-D Fast-ion DData

ITPA Diagnostics 4/06

Fast-ion D-Alpha Diagnostic Measures Flat Fast-ion Profiles during Strong Alfven Activity

Heidbrink, IAEA Synopsis (2006)

DIII-D data

•If ITER operates with reversed shear, Reversed Shear Alfven Eigenmodes (RSAE) are likely.

ITPA Diagnostics 4/06

Vertical Views of the Fast-ion Profile Address a Crucial ITER Issue

•On both theoretical and empirical grounds, the fast-ion profile will vary with major radius R, not just minor radius.

•A key scientific issue for ITER is alpha-driven instabilities and the resultant alpha transport.

•Vertical camera views are far more sensitive to the expected transport than horizontal views.

Internal fluctuation diagnostics (such as high bandwidth reflectometers or interferometers) are also crucial for the study of alpha-driven instabilities.