Multi-View, Simultaneous Measurements of Helicon Plasma Emission Lights using High-Speed Camera

Most electric thrusters have a short lifetime because of their electrode damages caused by a direct contact between electrodes and plasmas. One of the ways to solve this problem is to develop a completely electrodeless plasma thruster [1]. To promote this scheme, it is necessary to measure detailed plasma parameters with spatial distributions, e.g., electron density. Here, we have proposed spectral measurement method using a high-speed camera to observe emission lights from the plasma with three fiberscopes, spectral filters and optical lenses, which can be located on any cross sections outside the plasma of the discharge tube. We utilized an Algebraic Reconstruction Technique (ART) [2] and Fourier-Bessel expansions method (F-B method) [3], using three fan-views to reconstruct a local intensity distribution from measured line-integrated values. This report shows estimations of measurements on Large Mirror Device (LMD) using these methods along with an Abel inversion technique. [1] S. Shinohara et al., IEEE Trans. on Plasma Sci., 42 (2014) 1245. [2] R. Gordon and G. T. Herman, Int. Rev. Cytol., 38 (2014) 111. [3] Y. Nagayama, J. Appl. Phys., 62 (1987) 2702.