Application of Advanced Millimeter/ Far-infrared Sources to Collective Thomson Scattering Plasma Diagnostics

The application of advanced millimeter/far infrared sources to substantially improve the effectiveness of collective Thomson scattering plasma diagnostics is discussed. Gyrotrons, C02 lasers and far infrared lasers which are optically pumped with CO 2 laser radiation can now provide important new capabilities in terms of combined high peak power and high average power, fine frequency tunability and a wide range of operating frequencies. Their capabilities can improve the signal to noise ratio and make possible time dependent scattering measurements. Both thermal level scattering used for determination of ion temperature and low level non-thermal measurements used for the investigation of plasma turbulence and wave phenomena are considered. Rapidly pulsed gyrotrons, C02, and optically pumped lasers can provide a range of combinations of high peak power and high energy during a given time interval. The use of this high peak power-high energy tradeoff capability to maximize signal to noise ratios is discussed. Dramatic reduction in stray light, using fine frequency source tunability and gas absorption cell technology, is also discussed. 205 Woskoboinikow et al.