Faraday Rotation of a Far-Infrared Laser Beam by a Small Theta-Pinch Plasma

Faraday rotation measurements have been made on a small theta‐pinch plasma using the 337, 128, 119, and 79 μm wavelength radiation of the HCN and $H_{2}O$ gas lasers. Rotation angles of up to 50 deg have been measured with an accuracy, set mainly by the laser source, estimated to be better than 10%. Enhancement or attenuation of the transmitted signal produced by density gradients in the plasma has been measured simultaneously to correct the rotation measurements. The Faraday rotation measurement confirms that a magnetic probe placed in the plasma perturbs the actual field present.