Prototype studies of the MFTF-B far-infrared interferometer

A far-infrared (FIR) laser interferometer operating at 185 μm (Difluoremethane) will be used to monitor line integrated plasma density in the high-density center-cell region of the MFTF-B device at the Lawrence Livermore National Laboratory. There are a number of unique physical constraints and performance goals requiring careful analysis. Therefore, at UCLA a series of prototype experiments have been conducted to establish the final system design. For example, detailed studies of dielectric waveguide propagation have been performed since the laser source will be located ∼ 20 m from the vacuum vessel. Other areas studied include the expected spatial resolution achievable in the 60-cm-diameter plasma located at the center of the 8-m-diameter vacuum vessel. In addition, the effects of phase front distortion, refraction, and vibration, together with feedback in a Michelson configuration have all been carefully addressed