Ion temperature profile deconvolution and corrections to confinement parameters in spheromaks

Abstract

The purpose of this work is to determine ion temperature profiles in spheromaks [Nucl. Fusion 19, 489 (1979)] for the first time. Knowledge of the ion temperature profile is necessary in the correct calculation of plasma confinement parameters. The work herein details the calculation of ion temperature profiles for the Compact Torus Experiment (CTX) [Nucl. Fusion 28, 1555 (1988)] and S-1 [Phys. Rev. Lett. 46, 188 (1981)] spheromaks. Data from single chord Doppler ion temperature measurements in these devices have been analyzed with the aid of a one-dimensional equilibrium charge state transport code. Using electron temperature and density profiles from Thomson scattering, and estimates for transport rates, a most probable position for the emission of line radiation can be determined and correlated with the measured Doppler ion temperature, thus generating an ion temperature profile. From this ion temperature profile determination, plasma confinement parameters for the small solid flux conserver CTX [Phys. Fluids B 2, 1342 (1990)] spheromak can be determined, and confinement parameters for S-1 can be reevaluated, eliminating the previous confinement calculations assumption Ti(r)=Te(r). The CTX device has a calculated volume averaged beta 〈β〉 ranging from 3% to 8% and a volume averaged energy confinement time 〈τE〉 between 14 and 35 μsec; while the S-1 spheromak has 〈β〉 between 15% and 40% and 〈τE〉 ranging from 30 to 70 μsec.