Interferometry Techniques on Fusion Plasmas

Abstract

AbstractOptical interferometry techniques allow phase changes in a medium to be accurately determined. Since plasmas introduce a phase modification proportional to electron density, interferometry has been used routinely to determine the time development of electron density profiles in magnetic confinement fusion plasmas. The present paper describes the basic principles of interferometry of plasmas and establishes criteria regarding wavelength selection, vibrational phase noise, phase averaging etc. In addition, recent advances at UCLA in interferometry of fusion plasmas will be described. For example, high spatial sampling has allowed the detailed study of MHD phenomena such as sawteeth and Mimov oscillations, and 2-D imaging interferometry has permitted tomographic reconstruction of electron density contours. Difficulties associated with interferometry on future fusion devices, such as CIT, will also be discussed together with possible solutions.