Fusion alpha particle diagnostics with gyrotrons

Collective Thomson scattering using long-pulse, millimeter-wave sources is potentially a powerful diagnostic technique of localized alpha particle velocity distribution and density in a fusion tokamak. The Doppler broadened scattered spectrum allows an unambiguous measurement of these parameters. The combination of a long-pulse and long-wavelength source optimizes the achievable signal to noise ratio. Additional advantages include large scattering angles up to 1800, wide-bandwidth receivers, and suitability in a radiation environment. Magnetized particle resonances will be averaged out by finite diagnostic beam divergence and frequency resolution. Millimeter-waves should be accessible to high-field tokamaks using extraordinary mode (x-mode) propagation at frequencies between the lower x-mode cutoff and the upper hybrid resonance