Abstract
A new diagnostic, aimed at energy-resolved measurements of the spatial and temporal dynamics of fast ions in NSTX plasmas, is described. It is based on active charge-exchange recombination spectroscopy. The fast-ion signal is inferred from light emitted in the wavelength range of the D(alpha) line by fast ions recombining with an injected neutral beam. Two complementary systems are operational. The first system, based on a spectrometer coupled to a charge coupled device detector, has 16 channels with space, time, and energy resolution of 5 cm, 10 ms, and 10 keV, respectively. The second system monitors the energy-integrated fast-ion signal on time scales of approximately 20 micros at three different radii. Signals are measured by a multianode photomultiplier tube. For both systems, each channel includes two paired views, intercepting and missing the neutral beam for a direct subtraction of the background signal not associated with fast ions. Examples of signals from the 2008 NSTX run are presented.
Highlights
Fast ions inside a plasma volume illuminated by a neutral beamNBcan undergo charge-exchange reactions
This paper describes the FIDA diagnostic system installed on NSTX
As anticipated in Ref. 10 two complementary instruments have been installed on NSTX
Summary
Fast ions inside a plasma volume illuminated by a neutral beamNBcan undergo charge-exchange reactions. The response function, WE , p ͒, accounts for the effective averaging over the phase space intrinsic to the method and for the specific viewing and beam geometry It contains the information on the recombination rate of fast ions, i.e.,. ̄v is an average impact velocity, andcxvis calculated by averaging over the known fractions of NB neutrals with different injection energies, including full, 1 / 2, and 1 / 3 energy components This approximate expression is justified by the fact that cx is a smooth function ofv for the energy range of interest, E տ 20 keV. The FIDA systems will naturally complement the information already available from the other NSTX fast-ion diagnostics, including neutral particle analyzers, neutron detectors, and a scintillator based energetic ion loss detector..
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
