Abstract
A fast-ion D-alpha (FIDA) diagnostic is under development for the National Spherical Torus Experiment (NSTX). The FIDA technique is a charge-exchange recombination spectroscopy measurement that exploits the large Doppler shift of Balmer-alpha light from energetic hydrogenic atoms to infer the fast-ion density. The principal objective of the NSTX installation is to measure the transport of beam ions caused by fast-ion driven instabilities; detection of perpendicular acceleration of fast ions during high harmonic fast wave heating is another important goal. Recent data from a DIII-D FIDA diagnostic guide the design. The planned NSTX diagnostic consists of two separate instruments focusing on different aspects of the measurement. One instrument uses a transmission grating spectrometer to measure the perpendicular energy spectrum and the spatial profile every 10ms; the anticipated resolution is ∼10keV in energy and ∼5cm in radius. A second instrument employs bandpass filters to detect fast-ion redistribution events with millisecond temporal resolution.
Highlights
The diagnosis of fast ions is an important element of the National Spherical Torus ExperimentNSTXprogram
The ideal fast-ion diagnostic would measure the entire distribution function in space, velocity, and time, f fr, E, vʈ / v, t. ͑Here E is the energy and vʈ / v is the pitch of the velocity vector relative to the magnetic field.͒ The fastion D-alphaFIDAconcept[3] measures light emitted by fast ions that neutralize when they pass through a heating beam
Since the DIII-D results demonstrate the feasibility of the D␣ technique, we discuss the NSTX design relative to DIII-D
Summary
R. E. Bell Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 W. Solomon Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 ͑Received 10 May 2006; presented on 10 May 2006; accepted 2 June 2006; published online 9 October 2006͒
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