Madison symmetric torus far‐infrared interferometer

A far‐infrared (FIR) interferometer plasma density diagnostic has been installed on the Madison Symmetric Torus (MST) at the University of Wisconsin at Madison. This collaborative experiment between University of California at Los Angeles and the University of Wisconsin at Madison has been undertaken to study the physics of the reversed field pinch magnetic confinement configuration. The density profile will be measured via an 11 channel FIR Interferometer. Since MST does not possess slotted plasma viewing ports, each channel will have an individual 4‐cm‐diam port in the vacuum vessel wall. In order to provide sufficient spatial sampling while minimizing field perturbations, the ports are positioned along two radial arms (separated by 5°) with five ports along one arm and six along the other. The FIR system consists of a tunable twin‐frequency FIR laser pumped by a tunable CO2 laser. The system will initially operate at 743 μm but can be discretely tuned from 185 to 1222 μm. This will allow the system to measure a wide range of density parameters. This paper will report and discuss the installation of the system and initial single‐chord data from the interferometer.