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Measurement of the D alpha spectrum produced by fast ions in DIII-D.

  • Author(s): Luo, Y
  • Heidbrink, WW
  • Burrell, KH
  • Kaplan, DH
  • Gohil, P
  • et al.

Published Web Location

https://doi.org/10.1063/1.2712806Creative Commons 'BY' version 4.0 license
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.

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