D2O Laser Thomson Scattering and Submillimeter Heterodyne Receiver Measurements

The MIT program to develop high power collective Thomson scattering diagnostics will be presented. All elements of a 385 μm D2O laser Thomson scattering diagnostic are in place and operational on the Alcator C tokamak. Major components include: a 0.5 MW, 150 ns D2O laser; a heterodyne receiver using a corner reflector mounted Schottky diode mixer and a 25 mW, 381 μm DCOOD laser local oscillator; and x-band I.F. electronics including a 32 channel multiplexer filter centered at 9.4 GHz with 80 MHz wide channels. Receiver noise temperatures (not including signal collection optics) of 15,000-20,000 K double sideband (DSB) have been measured for individual filter channels. Additional details of the D2O laser, the receiver and the overall implementation of this diagnostic on Alcator C have been described previously [1-3].