title: Measurement of the D alpha spectrum produced by fast ions in DIII-D.
abstract: Fast ions are produced by neutral beam injection and ion cyclotron heating in toroidal magnetic fusion devices. As deuterium fast ions orbit around the device and pass through a neutral beam, some deuterons neutralize and emit D(alpha) light. For a favorable viewing geometry, the emission is Doppler shifted away from other bright interfering signals. In the 2005 campaign, we built a two channel charge-coupled device based diagnostic to measure the fast-ion velocity distribution and spatial profile under a wide variety of operating conditions. Fast-ion data are acquired with a time resolution of approximately 1 ms, spatial resolution of approximately 5 cm, and energy resolution of approximately 10 keV. Background subtraction and fitting techniques eliminate various contaminants in the spectrum. Neutral particle and neutron diagnostics corroborate the D(alpha) measurement. Examples of fast-ion slowing down and pitch angle scattering in quiescent plasma and fast-ion acceleration by high harmonic ion cyclotron heating are presented.
authors.affiliation: University of California, Irvine, CA 92697, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Luo
authors.forename: W W
authors.initials: WW
authors.lastname: Heidbrink
authors.forename: K H
authors.initials: KH
authors.lastname: Burrell
authors.forename: D H
authors.initials: DH
authors.lastname: Kaplan
authors.forename: P
authors.initials: P
authors.lastname: Gohil