Fractional Fringe HCN Laser-Interferometer

Abstract

An HeN laser-inte~ferometer is report.ed with better than 1/100 of a fringe phase shift sensitivity at a wavelengt~ ~; 33~:-Apphed to plasm~ densl~y measur~men~ this corresponds to electron density line integrals of ~.3 X 10 em ?r lower: The fractional frmge techmque mvolves sinusoidally driving the reference path mirror m a focused Mlc~el~on mterferomet~r; changes in the effective path length alter the relative magnitude of even and odd harmomcs m the resultant mterferometer signal. Results are shown from application of this diagnostic to the Burnout V plasma.