TFTR 60-GHZ ALPHA-PARTICLE COLLECTIVE THOMSON SCATTERING DIAGNOSTIC

A 60 GHz gyrotron collective Thomson scattering alpha particle diagnostic has been implemented for the D-T period on the Tokamak Fusion Test Reactor (TFTR). Gyrotron power of 0.1-1 kW in pulses of up to 1 s can be launched in X mode. Efficient corrugated waveguides are used with antennas and vacuum windows of the TFTR Microwave Scattering system. A multichannel synchronous detector receiver system and spectrum analyzer acquire the scattered signals. A 200 megasample/s digitizer and spectrum analyzer are used to resolve fine structure in the frequency spectrum. By scattering nearly perpendicular to the magnetic field, this experiment will take advantage of an enhancement of the scattered signal which results from the interaction of energetic ions with plasma resonances in the lower hybrid frequency range. Significant enhancements are expected with D-T fusion alpha particles, which should be detectable with gyrotron power of less than 1 kW, while maintaining an acceptable signal-to-noise ratio. This diagnostic will be the first experimental test of recent collective Thomson scattering models and should also provide an indication of the presence of energetic alpha particles in the core of TFTR. © 1995 American Institute of Physics.