A Multi-Reflection Type Visible-Laser Interferometer for High Density Plasma Measurements

Abstract

In order to measure a high density plasma more than 10²⁰ m^-3 in the vicinity of a magneto-plasma-dynamic arcjet (MPDA), a visible-laser interferometer is fabricated using a He-Ne laser (λ = 632.8 nm). As it doesn't have enough phase shift when the light passes through the MPDA plasma once, we adopt a multi-reflection optical system in this interferometer to improve the phase sensitivity. We measured a plasma density by the interferometer and estimated the maximum value of line-integrated density of 4 × 10¹⁹ m^-2 . These experimental results are consistent with that of electrostatic probe measurement in the downstream region.