High sensitivity far infrared laser diagnostics for the C 2U advanced beam driven field reversed configuration plasmas.
A high sensitivity multi channel far infrared laser diagnostics with switchable interferometry and polarimetry operation modes for the advanced neutral beam driven C 2U field reversed configuration (FRC) plasmas is described. The interferometer achieved superior resolution of 1 x 1016 m 2 at >1.5 MHz bandwidth, illustrated by measurement of small amplitude high frequency fluctuations. The polarimetry achieved 0.04deg instrument resolution and 0.1deg actual resolution in the challenging high density gradient environment with >0.5 MHz bandwidth, making it suitable for weak internal magnetic field measurements in the C 2U plasmas, where the maximum Faraday rotation angle is less than 1deg. The polarimetry resolution data is analyzed, and high resolution Faraday rotation data in C 2U is presented together with direct evidences of field reversal in FRC magnetic structure obtained for the first time by a non perturbative method.
The Review of scientific instruments