Two-chord interferometry using 3.39 μm He-Ne laser on a flux-coil-generated FRC

Gota, H.; Bolte, N.; Deng, B. H.; Gupta, D.; Kiyashko, V.; Knapp, K.; Mendoza, R.; Morehouse, M.; Roche, T.; Wessel, F.
October 2010
Review of Scientific Instruments;Oct2010, Vol. 81 Issue 10, p10D512
Academic Journal
A two-chord λIR∼3.39 μm He-Ne laser interferometer system was developed for a flux-coil-generated field-reversed configuration to estimate the electron density and the total temperature of the field-reversed configuration (FRC) plasma. This two-chord heterodyne interferometer system consists of a single ∼2 mW infrared He-Ne laser, a visible (λvis∼632.8 nm) He-Ne laser for the alignment, a 40 MHz acousto-optic modulator, photodetectors, and quadrature phase detectors. Initial measurement was performed and the measured average electron densities were 2-10×1019 m-3 at two different radial positions in the midplane. A time shift in density was observed as the FRC expands radially. The time evolution of the line-averaged density agrees with the density estimated from the in situ internal magnetic probes, based on a rigid-rotor profile model.


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