The unfolding of multichord Doppler spectrometry

N. J. Conway, P. G. Carolan, M. R. Tournianski
1999 Review of Scientific Instruments  
A 20-chord Doppler spectrometer is used on the START spherical tokamak to record charge-exchange recombination ͑CXR͒ spectra ͑C 5ϩ 5291 Å, nϭ8→7͒. "Passive" radiation, mostly from near the plasma edge, is also present, and comes from electron-impact excitation of C 5ϩ as well as C 6ϩ CXR due to thermal neutrals. The relatively wide neutral beam, together with the blending of the passive and active emission, present difficult unfolding problems. These are overcome by imposing physics constraints
more » ... physics constraints such as constant ion temperatures on equilibrium magnetic flux surfaces. It is also necessary to model the beam-neutral atom density throughout the viewed equatorial plane. A nonlinear least-squares fitting code, using suitable profile parametrization, gives unfolded T i (r) and v (r) profiles. These are presented along with estimates of the errors on the profiles.
doi:10.1063/1.1149471 fatcat:buscctplm5er5lvfssdpzl2yti