| IT15 · D-Alpha Measurements of the Fast-ion Distribution Function in DIII-D
W.W. Heidbrink1, Y. Luo1, K.H. Burrell2 and the DIII-D Team
1University of California, Irvine
2General Atomics
Abstract: Hydrogenic fast-ion populations are common in toroidal magnetic fusion devices, especially in devices with neutral beam injection. As the fast ions orbit around the device and pass through a neutral beam, some fast ions neutralize and emit Balmer-alpha light. The intensity of this emission is weak compared to the signals from the injected neutrals, the warm (halo) neutrals, and the cold edge neutrals but, for a favorable viewing geometry, the emission is detectable. The intrinsic spatial resolution of the technique is ~5 cm for 40 keV/amu fast ions; the energy resolution is ~10 keV. In DIII-D experiments, we have measured the fast-ion velocity distribution and spatial profile under a wide variety of operating conditions. The technique is best suited for measurements of ~ 40 keV/amu hydrogenic fast ions but useful information on the confinement of 1000 keV deuterium beam ions in ITER may be obtainable.
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