LOCALIZED MAGNETIC-FIELD PITCH ANGLE MEASUREMENTS BY COLLECTIVE THOMSON SCATTERING

A novel new method is proposed to measure the internal magnetic field pitch angle in tokamaks by measuring the frequency of the lower hybrid resonance in the collective Thomson scattered spectrum. The resonance frequency has a dependence of 1.2 and 2.0 GHz/deg pitch angle for ITER and C-MOD-like plasma parameters, respectively, using a submillimeter-wave diagnostic source. Sensitivity to other plasma parameters such as electron density, temperature, energetic ion fraction, and magnetic field is shown to be weak.