Measurement of the Faraday Rotation of a Laser Beam Passing through a θ-Pinch Plasma

Abstract

Faraday rotation of a beam of light is discussed as a means of determining the magnetic field within a plasma and the relative merits of various detection systems are considered. Apparatus is described for measuring the rotation of the plane of polarization of a He–Ne laser beam at 6328 Å on passing through a small θ‐pinch plasma. Using a differential detection system of risetime 0.3 μsec, an observed peak rotation of 1.0 mrad can be measured to an accuracy of 10%. Deviation of the beam by electron‐density gradients within the plasma is shown to be small and readily compensated for. Good agreement is obtained between the measurements of Faraday rotation and independent measurements of the magnetic field using magnetic probes.