A CO₂ laser tangential imaging system for CDX‐U (abstract)

In a previous paper [R. Nazikian and B. Grek, Rev. Sci. Instrum. 61, 2899 (1990)], it was shown that tangential imaging provides a powerful new technique for rendering two‐dimensional images of local density fluctuations in toroidal plasma devices. The technique consists of projecting a CO₂ laser beam tangent to magnetic field lines at the plasma midplane and using phase contrast or other related optical methods for imaging line integral density fluctuations. In this paper we present recent progress in the development of such an imaging system for CDX‐U. The interferometer makes use of a novel variation on the Zernike phase contrast method for detecting phase variations impressed on laser beams propagating through random media. This work supported by Department of Energy contract No. DE‐AC02‐76‐CHO‐3073.