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 ( n e ) and 6% in the electron temperature ( T e ) at n e = 4 × 10 19 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 × 10 17 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 n e and T e measurement is 7 × 10 20 ∕ n e J , which means that single shot measurements are possible for n e > 2 × 10 21 m − 3 .