An infrared Schlieren interferometer for measuring electron density profiles

In rotationally symmetric plasmas one can determine the electron density profiles from refractive index effects, preferably by using infrared radiation. In this report the diagnostic value of schlieren techniques is compared to that of interferometry. As a very efficient diagnostic setup, a combined schlieren interferometer is introduced, which makes use of the plasma itself as a beam-splitter. Experimentally, arc plasmas are investigated using the infrared radiation of a CO 2 -laser at 10.6 mu wavelength.