High sensitivity imaging Thomson scattering for low temperature plasma

A highly sensitive imaging Thomson scattering system was developed for low temperature (0.1–10 eV) plasma applications at the Pilot-PSI linear plasma generator. The essential parts of the diagnostic are a neodymium doped yttrium aluminum garnet laser operating at the second harmonic (532 nm), a laser beam line with a unique stray light suppression system and a detection branch consisting of a Littrow spectrometer equipped with an efficient detector based on a Generation III image intensifier combined with an intensified charged coupled device camera. The system is capable of measuring electron density and temperature profiles of a plasma column of 30 mm in diameter with a spatial resolution of 0.6 mm and an observational error of 3% in the electron density (ne) and 6% in the electron temperature (Te) at ne=4×1019 m-3. This is achievable at an accumulated laser input energy of 11 J (from 30 laser pulses at 10 Hz repetition frequency). The stray light contribution is below 9×1017 m-3 in electron density equivalents by the application of a unique stray light suppression system. The amount of laser energy that is required for a ne and Te measurement is 7×1020/ne J, which means that single shot measurements are possible for ne>2×1021 m-3