Comparison of CTS Signals due to NBI heating and Alphas in ITER

Introduction Collective Thomson scattering (CTS) has, among other potentials, the capability to allow observation of confined fast ions in plasmas. The technique has been demonstrated at JET [1] and TEXTOR [2]. The proposed CTS system for ITER is designed to employ millimeter waves at 60 GHz emitted by 1 MW gyrotrons [3]. The spectral power density of scattered waves in this frequency range leaving the plasma can be measured and a number of plasma parameters can be inferred. With the proposed ITER CTS system it is possible to measure time-resolved fast ion velocity distributions in several measurement volumes simultaneously, which are given by overlaps of probe and receiver beams [3]. The resolved velocity direction in each volume is then given by the fluctuation wave vector k = ks −ki where ks is the wave vector of the scattered radiation (receiver beam) and ki is the wave vector of the incident radiation (probe beam).