Collective Thomson scattering in tokomaks having energetic ions

Summary Form only given, as follows. Collective Thomson scattering (CTS) of electromagnetic waves occurs when the effective wavelength of the incoming radiation is larger than the Debye length. Under these circumstances, the electrons surrounding a fast ion radiate collectively to produce a wave that is Doppler-shifted by the ion velocity. Recent theoretical analysis suggests that an energetic (200-800 keV) He/sup 3/ minority can be produced in TFTR by ion cyclotron heating (ICH). Since the ICH-generated distribution is non-Maxwellian, the authors have generalized the theoretical analysis of CTS to allow for particle distributions which can be represented by various orthogonal polynomial expansions. They have evaluated the efficacy of CTS in detecting a fast He/sup 3/ component and determined the sensitivity of the diagnostic to the details of the ion distribution. In particular, the effectiveness of a planned 56-GHz gyrotron CTS diagnostic for TFTR has been evaluated. Detailed spectrum calculations will allow refinement of the scattering geometry, spectrum analysis electronics, required bandwidth, and resolution, and allow estimates of the expected signal-to-noise ratio.<>