PPPL-3718 is available in pdf format (624 KB).

Initial Neutral Particle Analyzer Measurements of Ion Temperature in NSTX

Authors: S.S. Medley, R.E. Bell, M.P. Petrov, A.L. Roquemore, and E.V. Suvorkin

Date of PPPL Report: July 2002

Presented at: the 14th Topical Conference on High Temperature Plasma Diagnostics, Madison, Wisconsin, July 8-11, 2002. Proceedings published in Review of Scientific Instruments 74 No. 3 (March 2003) 1896-1899.

The Neutral Particle Analyzer (NPA) diagnostic on the National Spherical Torus Experiment (NSTX) utilizes a PPPL-designed E||B spectrometer which measures the energy spectra of minority H and bulk D species simultaneously with 39 energy channels per mass specie and a time resolution of 1 msec. The calibrated energy range is E = 0.5 -150 keV and the energy resolution varies from DE/E = 3-7% over the surface of the microchannel plate detector. The NPA measures thermal Maxwellian ion spectra to obtain line integrated ion temperatures, Ti. For line integral electron densities below neL ~ 3.5 x 1019 m-2, good agreement is observed between the line integrated NPA Ti and the central Ti(0) measured by the spatially localized CHarge Exchange Recombination Spectroscopy (CHERS) diagnostic. However, with increasingly higher neL the NPA Ti falls below the central Ti(0) measured by CHERS because the charge exchange neutral emissivity weights the line integrated NPA measurement outboard of the plasma core. An analytic neutral analysis code, DOUBLE, has been applied to the NPA data to correct for this effect and restore agreement with Ti(0) measured by CHERS. A description of the NPA diagnostic on NSTX and initial ion temperature measurements along with an illustration of application of the DOUBLE code are presented.