A three-dimensional Gaussian-beam ray-tracing program for designing interferometer/polarimeter plasma diagnostics

We have developed a three-dimensional Gaussian-beam ray-tracing program to aid in the design of infrared, far-infrared, and millimeter wave interferometer and polarimeter diagnostic systems for magnetic confinement fusion relevant plasma physics experiments. An overview of the program is presented along with a description of the ray-tracing algorithm. A model is developed for the case of diffraction of a Gaussian beam off a cylindrical grating and is shown to be in good agreement with experimental measurements. The program has been used to aid the design of the scanning-grating interferometer system for the H-1NF heliac experimental plasma device. The program is written in the Research Systems Inc. Interactive Data Language and, on a typical modern personal computer, is able to trace and render the ∼50 element three-view 44-beam H-1NF interferometer optical system in about one minute.